minSdk 19

Great catch, thanks!

.buildscript/deploy_snapshot.sh

@@ -1,26 +0,0 @@
-#!/bin/bash
-#
-# Deploy a jar, source jar, and javadoc jar to Sonatype's snapshot repo.
-#
-# Adapted from https://coderwall.com/p/9b_lfq and
-# http://benlimmer.com/2013/12/26/automatically-publish-javadoc-to-gh-pages-with-travis-ci/
-
-SLUG="bluelinelabs/Conductor"
-JDK="oraclejdk8"
-BRANCH="develop"
-
-set -e
-
-if [ "$TRAVIS_REPO_SLUG" != "$SLUG" ]; then
-  echo "Skipping snapshot deployment: wrong repository. Expected '$SLUG' but was '$TRAVIS_REPO_SLUG'."
-elif [ "$TRAVIS_JDK_VERSION" != "$JDK" ]; then
-  echo "Skipping snapshot deployment: wrong JDK. Expected '$JDK' but was '$TRAVIS_JDK_VERSION'."
-elif [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
-  echo "Skipping snapshot deployment: was pull request."
-elif [ "$TRAVIS_BRANCH" != "$BRANCH" ]; then
-  echo "Skipping snapshot deployment: wrong branch. Expected '$BRANCH' but was '$TRAVIS_BRANCH'."
-else
-  echo "Deploying snapshot..."
-  ./gradlew clean uploadArchives
-  echo "Snapshot deployed!"
-fi

.editorconfig

@@ -0,0 +1,25 @@
+root = true
+
+[*.{java,kt,kts,xml,gradle}]
+charset=utf-8
+end_of_line=lf
+max_line_length=120
+insert_final_newline=true
+trim_trailing_whitespace=true
+indent_style=space
+
+[*.{java,kt,kts,gradle}]
+spaces_around_operators=true
+indent_brace_style=K&R
+
+[*.{java,gradle}]
+indent_size=4
+
+[*.{kt,kts}]
+indent_size=2
+continuation_indent_size=2
+ij_kotlin_allow_trailing_comma=true
+ij_kotlin_allow_trailing_comma_on_call_site=true
+
+[*.xml]
+indent_size=2

.github/workflows/main.yml

@@ -0,0 +1,38 @@
+name: Test & Publish
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: set up JDK 17
+      uses: actions/setup-java@v2
+      with:
+        distribution: 'adopt'
+        java-version: '17'
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Test with Gradle
+      run: ./gradlew test
+  publish:
+    runs-on: ubuntu-latest
+    if: github.ref == 'refs/heads/develop'
+    needs: test
+ 
+    steps:
+    - uses: actions/checkout@v2
+    - name: set up JDK 17
+      uses: actions/setup-java@v2
+      with:
+        distribution: 'adopt'
+        java-version: '17'
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Release with Gradle
+      run: ./gradlew clean publishAllPublicationsToMavenCentral
+      env:
+        ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.SONATYPE_NEXUS_USERNAME }}
+        ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.SONATYPE_NEXUS_PASSWORD }}

.gitignore

@@ -5,10 +5,11 @@
 .checkstyle
 
 # IntelliJ IDEA
-.idea
 *.iml
 *.ipr
 *.iws
+/.idea/*
+!/.idea/scopes/
 classes
 gen-external-apklibs
 
@@ -35,6 +36,4 @@ pom.xml.*
 local.properties
 
 *.prefs
-
-# The keystore file
-app/spothero-release.keystore
+.DS_Store

.idea/.gitignore

@@ -0,0 +1,9 @@
+/libraries
+/runConfigurations.xml
+/misc.xml
+/vcs.xml
+/workspace.xml
+/caches
+/gradle.xml
+/modules.xml
+/compiler.xml

.idea/encodings.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="PROJECT" charset="UTF-8" />
+  </component>
+</project>

.travis.yml

@@ -1,35 +0,0 @@
-language: android
-
-android:
-  components:
-    - tools
-    - build-tools-25.0.3
-    - android-25
-    - extra-android-m2repository
-  licenses:
-    - '.+'
-
-script:
-  - ./gradlew test
-
-jdk:
-  - oraclejdk8
-
-branches:
-  only:
-    - develop
-    - master
-
-after_success:
-  - .buildscript/deploy_snapshot.sh
-
-cache:
-  directories:
-    - $HOME/.gradle
-
-sudo: false
-
-env:
-  global:
-    - secure: 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
-    - secure: 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

CONTRIBUTING.md

@@ -0,0 +1,70 @@
+# Community Contribution Guidelines
+
+As the creators and maintainers of this project, we want to ensure that the project lives and continues to grow. Not blocked by any singular person's computer time. One of the simplest ways of doing this is by encouraging a larger set of shallow contributors. Through this, we hope to mitigate the problems of a project that needs updates, but there is no-one who has the power to do so.
+
+#### Development Process
+
+We maintain two permanent, protected branches: `master` and `development`.
+
+`master` is for the current release. It has already been distributed to jcenter and can't be modified at this point (except for docs that may be incorrect for the current release!).
+
+`development` is where we stage work for the *next* release. Pull requests should be directed to this branch.
+
+When working on a new feature or fix that may span multiple commits, please do so in a feature branch (ex: `feature/my_cool_thing`). Please clean up these feature branches once merged into `development`.
+
+When a new version is ready to be released, please create a pull request to merge `development` into `master`, named something like "Release 10.0". Then we can have some final discussion before we merge it into `master` and push the release out to the public.
+
+Since `development` is a *shared* branch, it is important not to ever rebase this branch onto `master`. If a bug fix is applied to `master` it can be merged into `development` using good old simple `git checkout development && git merge master`. Yes this will clutter the history a little bit, but it also provides important context to know how/when a patch was applied. Merge commits can be considered necessary historical data, not warts on an idealized history graph.
+
+#### Testing
+
+To run tests locally, just run `./gradlew test`. Tests should always be run before pushing anything to the repo.
+
+#### Ownership
+
+If you get a merged pull-request of substance (ie not just a typo fix), then you are eligible for push access to this repo. Simply request access via a new GitHub issue.
+
+Offhand, it is easy to imagine that this would make code quality suffer, but in reality it offers fresh perspectives to the codebase and encourages ownership from people who are depending on the project. If you are building a project that relies on this codebase, then you probably have the skills to improve it and offer valuable feedback. At the end of the day, there isn't too much risk in this, as the `master` branch is still locked, and jcenter access is still being restricted.
+
+Everyone comes in with their own perspective on what a project could/should look like, and encouraging discussion can help expose good ideas sooner.
+
+#### Why do we give out push access?
+
+It can be overwhelming to be offered the chance to wipe the source code for a project. Do not worry, we do not let you push to master. All code is peer-reviewed, and we have the convention that someone other than the submitter should merge non-trivial pull requests.
+
+As a contributor, you can merge other people's pull requests, or other contributors can merge yours. You will not be assigned a pull request, but you are welcome to jump in and take a code review on topics that interest you.
+
+This project is not continuously deployed, there is space for debate after review too. Offering everyone the chance to revert, or make an amending pull request. If it feels right, merge.
+
+#### How can we help you get comfortable contributing?
+
+It is normal for a first pull request to be a potential fix for a problem, and moving on from there to helping the project's direction can be difficult. We will try to help contributors cross that barrier by offering good first step issues. These issues can be fixed without feeling like you are stepping on toes. Ideally, these are non-critical issues that are well defined. They will be purposely avoided by mature contributors to the project, to make space for others.
+
+We aim to keep all project discussion inside GitHub issues. This is to make sure valuable discussion is accessible via search. If you have questions about how to use the library, or how the project is running - GitHub issues are the goto tool for this project.
+
+#### Our expectations on you as a contributor
+
+To quote [@alloy](https://github.com/alloy) from [this issue](https://github.com/Moya/Moya/issues/135):
+
+> Do not ever feel bad for not contributing to open source.
+
+We want contributors to provide ideas, keep the ship shipping and to take some of the load from others. It is non-obligatory; we’re here to get things done in an enjoyable way. :trophy:
+
+The fact that you will have push access will allow you to:
+
+- Avoid having to fork the project if you want to submit other pull requests, as you will be able to create branches directly on the project.
+- Help triage issues and merge pull requests.
+- Pick up the project if other maintainers move their focus elsewhere.
+
+It is up to you to use those superpowers or not though 😉
+
+If someone submits a pull request that is not perfect, and you are reviewing, it is better to think about the PR's motivation rather than the specific implementation. Having braces on the wrong line should not be a blocker. Though we do want to keep test coverage high, we will work with you to figure that out together.
+
+#### What about if you have problems that cannot be discussed in a public issue?
+
+[Eric Kuck](https://github.com/erickuck) has a contactable email on his GitHub profile, and is happy to talk about any problems.
+
+#### This is a different way to handle open source! Where did it come from?
+
+The original source of this document can be found at [https://github.com/moya/contributors](https://github.com/moya/contributors).
+

README.md

@@ -1,4 +1,4 @@
-[![Travis Build](https://travis-ci.org/bluelinelabs/Conductor.svg)](https://travis-ci.org/bluelinelabs/Conductor) [![Android Arsenal](https://img.shields.io/badge/Android%20Arsenal-Conductor-brightgreen.svg?style=flat)](http://android-arsenal.com/details/1/3361) [![Javadocs](http://javadoc.io/badge/com.bluelinelabs/conductor.svg)](http://javadoc.io/doc/com.bluelinelabs/conductor)
+[![GitHub Actions Workflow](https://github.com/bluelinelabs/conductor/actions/workflows/main.yml/badge.svg)](https://github.com/bluelinelabs/conductor/actions/workflows/main.yml) [![Android Arsenal](https://img.shields.io/badge/Android%20Arsenal-Conductor-brightgreen.svg?style=flat)](http://android-arsenal.com/details/1/3361) [![Javadocs](http://javadoc.io/badge/com.bluelinelabs/conductor.svg)](http://javadoc.io/doc/com.bluelinelabs/conductor)
 
 # Conductor
 
@@ -13,42 +13,42 @@ A small, yet full-featured framework that allows building View-based Android app
 :twisted_rightwards_arrows: | Beautiful transitions between views
 :floppy_disk: | State persistence
 :phone: | Callbacks for onActivityResult, onRequestPermissionsResult, etc
-:european_post_office: | MVP / MVVM / VIPER / MVC ready
+:european_post_office: | MVP / MVVM / MVI / VIPER / MVC ready
 
 Conductor is architecture-agnostic and does not try to force any design decisions on the developer. We here at BlueLine Labs tend to use either MVP or MVVM, but it would work equally well with standard MVC or whatever else you want to throw at it.
 
 ## Installation
 
+Conductor 4.0 is coming soon. It is already being used in production with many, many millions of users. It is, however, not guaranteed to be API stable. As such, it is being released as a preview rather than a standard release. Preview in this context is _not_ a commentary on stability. It is considered to be up to the same quality standards as the current 3.x stable release.
+Changes in Conductor 4 are available in the [GitHub releases](https://github.com/bluelinelabs/Conductor/releases/). In preparation for the release of the next version, there are currently 3 installation options:
+
+### Latest Stable 3.x
 ```gradle
-compile 'com.bluelinelabs:conductor:2.1.4'
+def conductorVersion = '3.2.0'
 
-// If you want the components that go along with
-// Android's support libraries (currently just a PagerAdapter):
-compile 'com.bluelinelabs:conductor-support:2.1.4'
+implementation "com.bluelinelabs:conductor:$conductorVersion"
 
-// If you want RxJava lifecycle support:
-compile 'com.bluelinelabs:conductor-rxlifecycle:2.1.4'
+// AndroidX Transition change handlers:
+implementation "com.bluelinelabs:conductor-androidx-transition:$conductorVersion"
 
-// If you want RxJava2 lifecycle support:
-compile 'com.bluelinelabs:conductor-rxlifecycle2:2.1.4'
+// ViewPager PagerAdapter:
+implementation "com.bluelinelabs:conductor-viewpager:$conductorVersion"
 
-// If you want RxJava2 Autodispose support:
-compile 'com.bluelinelabs:conductor-autodispose:2.1.4'
-
-// If you want Controllers that are Lifecycle-aware (architecture components):
-compile 'com.bluelinelabs:conductor-arch-components-lifecycle:0.1.1'
+// ViewPager2 Adapter:
+implementation "com.bluelinelabs:conductor-viewpager2:$conductorVersion"
 ```
 
-SNAPSHOT:
+### 4.0 Preview
+Use `4.0.0-preview-4` as your version number in any of the dependencies above.
 
-Just use `2.1.5-SNAPSHOT` as your version number in any of the above dependencies and add the url to the snapshot repository:
+### SNAPSHOT
+Use `4.0.0-SNAPSHOT` as your version number in any of the dependencies above and add the url to the snapshot repository:
 
 ```gradle
 allprojects {
   repositories {
-    ...
-
     maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }
+  }
 }
 ```
 
@@ -59,53 +59,49 @@ allprojects {
 __Controller__ | The Controller is the View wrapper that will give you all of your lifecycle management features. Think of it as a lighter-weight and more predictable Fragment alternative with an easier to manage lifecycle.
 __Router__ | A Router implements navigation and backstack handling for Controllers. Router objects are attached to Activity/containing ViewGroup pairs. Routers do not directly render or push Views to the container ViewGroup, but instead defer this responsibility to the ControllerChangeHandler specified in a given transaction.
 __ControllerChangeHandler__ | ControllerChangeHandlers are responsible for swapping the View for one Controller to the View of another. They can be useful for performing animations and transitions between Controllers. Several default ControllerChangeHandlers are included.
-__ControllerTransaction__ | Transactions are used to define data about adding Controllers. RouterControllerTransactions are used to push a Controller to a Router with specified ControllerChangeHandlers, while ChildControllerTransactions are used to add child Controllers.
+__RouterTransaction__ | Transactions are used to define data about adding Controllers. RouterTransactions are used to push a Controller to a Router with specified ControllerChangeHandlers, while ChildControllerTransactions are used to add child Controllers.
 
 ## Getting Started
 
 ### Minimal Activity implementation
 
-```java
-public class MainActivity extends Activity {
+```kotlin
+class MainActivity : AppCompatActivity() {
 
-    private Router router;
+    private lateinit var router: Router
 
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
+    override fun onCreate(savedInstanceState: Bundle?) {
+      super.onCreate(savedInstanceState)
 
-        setContentView(R.layout.activity_main);
+      setContentView(R.layout.activity_main)
 
-        ViewGroup container = (ViewGroup)findViewById(R.id.controller_container);
+      val container = findViewById<ViewGroup>(R.id.controller_container)
 
-        router = Conductor.attachRouter(this, container, savedInstanceState);
-        if (!router.hasRootController()) {
-            router.setRoot(RouterTransaction.with(new HomeController()));
-        }
+      router = Conductor.attachRouter(this, binding.controllerContainer, savedInstanceState)
+        .setPopRootControllerMode(PopRootControllerMode.NEVER)
+        .setOnBackPressedDispatcherEnabled(true)
+
+      if (!router.hasRootController()) {
+        router.setRoot(RouterTransaction.with(HomeController()))
+      }
     }
-
-    @Override
-    public void onBackPressed() {
-        if (!router.handleBack()) {
-            super.onBackPressed();
-        }
-    }
-
 }
 ```
 
 ### Minimal Controller implementation
 
-```java
-public class HomeController extends Controller {
-
-    @Override
-    protected View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container) {
-        View view = inflater.inflate(R.layout.controller_home, container, false);
-        ((TextView)view.findViewById(R.id.tv_title)).setText("Hello World");
-        return view;
-    }
+```kotlin
+class HomeController : Controller() {
 
+  override fun onCreateView(
+    inflater: LayoutInflater,
+    container: ViewGroup,
+    savedViewState: Bundle?
+  ): View {
+    val view = inflater.inflate(R.layout.controller_home, container, false)
+    view.findViewById<TextView>(R.id.tv_title).text = "Hello World"
+    return view  
+  }
 }
 ```
 
@@ -131,11 +127,19 @@ The lifecycle of a Controller is significantly simpler to understand than that o
 `getChildRouter` can be called on a `Controller` in order to get a nested `Router` into which child `Controller`s can be pushed. This enables creating advanced layouts, such as Master/Detail.
 
 ### RxJava Lifecycle
-If the RxLifecycle dependency has been added, there is an `RxController` available that can be used along with the standard [RxLifecycle library](https://github.com/trello/RxLifecycle). There is also a `ControllerLifecycleProvider` available if you do not wish to use this subclass.
+If the AutoDispose dependency has been added, there is a `ControllerScopeProvider` available that can be used along with the standard [AutoDispose library](https://github.com/uber/AutoDispose).
+
+## Community Projects
+The community has provided several helpful modules to make developing apps with Conductor even easier. Here's a collection of helpful libraries:
+
+* [ConductorGlide](https://github.com/MkhytarMkhoian/ConductorGlide) - Adds Glide lifecycle support to Controllers
+* [ConductorDialog](https://github.com/MkhytarMkhoian/ConductorDialog) - Adds a helpful DialogController (a Conductor version of DialogFragment)
+* [Mosby-Conductor](https://github.com/sockeqwe/mosby-conductor) - A plugin to integrate Mosby, an MVP/MVI library
+
 
 ## License
 ```
-Copyright 2016 BlueLine Labs, Inc.
+Copyright 2020 BlueLine Labs, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.

build.gradle

@@ -1,18 +1,29 @@
 buildscript {
     repositories {
-        jcenter()
+        mavenCentral()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.2'
+        classpath libs.agp
+        classpath libs.kotlin.plugin
+        classpath libs.dokka
     }
 }
 
 allprojects {
-    repositories {
-        jcenter()
-        mavenCentral()
-        maven { url 'https://maven.google.com' }
+    if (project.hasProperty('maven_publish_url')) {
+        pluginManager.withPlugin("com.vanniktech.maven.publish") {
+            publishing {
+                repositories {
+                    maven {
+                        url = maven_publish_url
+                        credentials {
+                            username = maven_publish_username
+                            password = maven_publish_password
+                        }
+                    }
+                }
+            }
+        }
     }
 }
-
-apply from: rootProject.file('dependencies.gradle')

conductor-lint/build.gradle

@@ -1,26 +1,21 @@
-apply plugin: 'java'
-
-targetCompatibility = JavaVersion.VERSION_1_7
-sourceCompatibility = JavaVersion.VERSION_1_7
+apply plugin: 'kotlin'
 
 configurations {
-    lintChecks
+    libs.lint.checks
 }
 
 dependencies {
-    compile rootProject.ext.lintapi
-    compile rootProject.ext.lintchecks
+    compileOnly libs.lint.api
+    compileOnly libs.lint.checks
+    compileOnly libs.kotlin.stdlib
 
-    testCompile rootProject.ext.lint
-    testCompile rootProject.ext.lintTests
-
-    lintChecks files(jar)
+    testImplementation libs.junit
+    testImplementation libs.lint
+    testImplementation libs.lint.tests
 }
 
 jar {
     manifest {
-        attributes('Lint-Registry': 'com.bluelinelabs.conductor.lint.IssueRegistry')
+        attributes('Lint-Registry-v2': 'com.bluelinelabs.conductor.lint.IssueRegistry')
     }
 }
-
-apply from: rootProject.file('dependencies.gradle')

conductor-lint/src/main/java/com/bluelinelabs/conductor/lint/ControllerChangeHandlerIssueDetector.java

@@ -1,6 +1,7 @@
 package com.bluelinelabs.conductor.lint;
 
 import com.android.tools.lint.client.api.JavaEvaluator;
+import com.android.tools.lint.client.api.UElementHandler;
 import com.android.tools.lint.detector.api.Category;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Implementation;
@@ -8,62 +9,80 @@ import com.android.tools.lint.detector.api.Issue;
 import com.android.tools.lint.detector.api.JavaContext;
 import com.android.tools.lint.detector.api.Scope;
 import com.android.tools.lint.detector.api.Severity;
-import com.intellij.psi.PsiClass;
-import com.intellij.psi.PsiMethod;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.uast.UClass;
+import org.jetbrains.uast.UElement;
+import org.jetbrains.uast.UMethod;
 
 import java.util.Collections;
 import java.util.List;
 
-public final class ControllerChangeHandlerIssueDetector extends Detector implements Detector.JavaPsiScanner {
+@SuppressWarnings("UnstableApiUsage")
+public final class ControllerChangeHandlerIssueDetector extends Detector implements Detector.UastScanner {
 
-    public static final Issue ISSUE =
+    static final Issue ISSUE =
             Issue.create("ValidControllerChangeHandler", "ControllerChangeHandler not instantiatable",
                     "Non-abstract ControllerChangeHandler instances must have a default constructor for the"
                             + " system to re-create them in the case of the process being killed.",
                     Category.CORRECTNESS, 6, Severity.FATAL,
                     new Implementation(ControllerChangeHandlerIssueDetector.class, Scope.JAVA_FILE_SCOPE));
 
-    public ControllerChangeHandlerIssueDetector() { }
+    private static final String CLASS_NAME = "com.bluelinelabs.conductor.ControllerChangeHandler";
 
     @Override
-    public List<String> applicableSuperClasses() {
-        return Collections.singletonList("com.bluelinelabs.conductor.ControllerChangeHandler");
+    public List<Class<? extends UElement>> getApplicableUastTypes() {
+        return Collections.<Class<? extends UElement>>singletonList(UClass.class);
     }
 
     @Override
-    public void checkClass(JavaContext context, PsiClass declaration) {
+    public UElementHandler createUastHandler(final JavaContext context) {
         final JavaEvaluator evaluator = context.getEvaluator();
-        if (evaluator.isAbstract(declaration)) {
-            return;
-        }
 
-        if (!evaluator.isPublic(declaration)) {
-            String message = String.format("This ControllerChangeHandler class should be public (%1$s)", declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-            return;
-        }
+        return new UElementHandler() {
 
-        if (declaration.getContainingClass() != null && !evaluator.isStatic(declaration)) {
-            String message = String.format("This ControllerChangeHandler inner class should be static (%1$s)", declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-            return;
-        }
+            @Override
+            public void visitClass(@NotNull UClass node) {
+                if (evaluator.isAbstract(node)) {
+                    return;
+                }
 
-        boolean hasDefaultConstructor = false;
-        PsiMethod[] constructors = declaration.getConstructors();
-        for (PsiMethod constructor : constructors) {
-            if (evaluator.isPublic(constructor)) {
-                if (constructor.getParameterList().getParametersCount() == 0) {
-                    hasDefaultConstructor = true;
-                    break;
+                final boolean hasSuperType = evaluator.extendsClass(node.getPsi(), CLASS_NAME, true);
+                if (!hasSuperType) {
+                    return;
+                }
+
+                if (!evaluator.isPublic(node)) {
+                    String message = String.format("This ControllerChangeHandler class should be public (%1$s)", node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
+                    return;
+                }
+
+                if (node.getContainingClass() != null && !evaluator.isStatic(node)) {
+                    String message = String.format("This ControllerChangeHandler inner class should be static (%1$s)", node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
+                    return;
+                }
+
+                boolean hasConstructor = false;
+                boolean hasDefaultConstructor = false;
+                for (UMethod method : node.getMethods()) {
+                    if (method.isConstructor()) {
+                        hasConstructor = true;
+                        if (evaluator.isPublic(method) && method.getUastParameters().size() == 0) {
+                            hasDefaultConstructor = true;
+                            break;
+                        }
+                    }
+                }
+
+                if (hasConstructor && !hasDefaultConstructor) {
+                    String message = String.format(
+                            "This ControllerChangeHandler needs to have a public default constructor (`%1$s`)", node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
                 }
             }
-        }
-
-        if (constructors.length > 0 && !hasDefaultConstructor) {
-            String message = String.format(
-                    "This ControllerChangeHandler needs to have a public default constructor (`%1$s`)", declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-        }
+        };
     }
+
 }

conductor-lint/src/main/java/com/bluelinelabs/conductor/lint/ControllerIssueDetector.java

@@ -2,6 +2,7 @@ package com.bluelinelabs.conductor.lint;
 
 import com.android.SdkConstants;
 import com.android.tools.lint.client.api.JavaEvaluator;
+import com.android.tools.lint.client.api.UElementHandler;
 import com.android.tools.lint.detector.api.Category;
 import com.android.tools.lint.detector.api.Detector;
 import com.android.tools.lint.detector.api.Implementation;
@@ -9,74 +10,90 @@ import com.android.tools.lint.detector.api.Issue;
 import com.android.tools.lint.detector.api.JavaContext;
 import com.android.tools.lint.detector.api.Scope;
 import com.android.tools.lint.detector.api.Severity;
-import com.intellij.psi.PsiClass;
-import com.intellij.psi.PsiMethod;
-import com.intellij.psi.PsiParameter;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.uast.UClass;
+import org.jetbrains.uast.UElement;
+import org.jetbrains.uast.UMethod;
+import org.jetbrains.uast.UParameter;
 
 import java.util.Collections;
 import java.util.List;
 
-public final class ControllerIssueDetector extends Detector implements Detector.JavaPsiScanner {
+@SuppressWarnings("UnstableApiUsage")
+public final class ControllerIssueDetector extends Detector implements Detector.UastScanner {
 
-    public static final Issue ISSUE =
+    static final Issue ISSUE =
             Issue.create("ValidController", "Controller not instantiatable",
                     "Non-abstract Controller instances must have a default or single-argument constructor"
                             + " that takes a Bundle in order for the system to re-create them in the"
                             + " case of the process being killed.", Category.CORRECTNESS, 6, Severity.FATAL,
                     new Implementation(ControllerIssueDetector.class, Scope.JAVA_FILE_SCOPE));
 
-    public ControllerIssueDetector() { }
+    private static final String CLASS_NAME = "com.bluelinelabs.conductor.Controller";
 
     @Override
-    public List<String> applicableSuperClasses() {
-        return Collections.singletonList("com.bluelinelabs.conductor.Controller");
+    public List<Class<? extends UElement>> getApplicableUastTypes() {
+        return Collections.singletonList(UClass.class);
     }
 
     @Override
-    public void checkClass(JavaContext context, PsiClass declaration) {
+    public UElementHandler createUastHandler(final JavaContext context) {
         final JavaEvaluator evaluator = context.getEvaluator();
-        if (evaluator.isAbstract(declaration)) {
-            return;
-        }
 
-        if (!evaluator.isPublic(declaration)) {
-            String message = String.format("This Controller class should be public (%1$s)", declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-            return;
-        }
+        return new UElementHandler() {
+            @Override
+            public void visitClass(@NotNull UClass node) {
+                if (evaluator.isAbstract(node)) {
+                    return;
+                }
 
-        if (declaration.getContainingClass() != null && !evaluator.isStatic(declaration)) {
-            String message = String.format("This Controller inner class should be static (%1$s)", declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-            return;
-        }
+                final boolean hasSuperType = evaluator.extendsClass(node.getPsi(), CLASS_NAME, true);
+                if (!hasSuperType) {
+                    return;
+                }
 
+                if (!evaluator.isPublic(node)) {
+                    String message = String.format("This Controller class should be public (%1$s)", node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
+                    return;
+                }
 
-        boolean hasDefaultConstructor = false;
-        boolean hasBundleConstructor = false;
-        PsiMethod[] constructors = declaration.getConstructors();
-        for (PsiMethod constructor : constructors) {
-            if (evaluator.isPublic(constructor)) {
-                PsiParameter[] parameters = constructor.getParameterList().getParameters();
+                if (node.getContainingClass() != null && !evaluator.isStatic(node)) {
+                    String message = String.format("This Controller inner class should be static (%1$s)", node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
+                    return;
+                }
 
-                if (parameters.length == 0) {
-                    hasDefaultConstructor = true;
-                    break;
-                } else if (parameters.length == 1 &&
-                        parameters[0].getType().equalsToText(SdkConstants.CLASS_BUNDLE) ||
-                        parameters[0].getType().equalsToText("Bundle")) {
-                    hasBundleConstructor = true;
-                    break;
+                boolean hasConstructor = false;
+                boolean hasDefaultConstructor = false;
+                boolean hasBundleConstructor = false;
+                for (UMethod method : node.getMethods()) {
+                    if (method.isConstructor()) {
+                        hasConstructor = true;
+                        if (evaluator.isPublic(method)) {
+                            List<UParameter> parameters = method.getUastParameters();
+                            if (parameters.size() == 0) {
+                                hasDefaultConstructor = true;
+                                break;
+                            } else if (parameters.size() == 1 &&
+                                    (parameters.get(0).getType().equalsToText(SdkConstants.CLASS_BUNDLE)) ||
+                                    parameters.get(0).getType().equalsToText("Bundle")) {
+                                hasBundleConstructor = true;
+                            }
+                        }
+                    }
+                }
+
+                if (hasConstructor && !hasDefaultConstructor && !hasBundleConstructor) {
+                    String message = String.format(
+                            "This Controller needs to have either a public default constructor or a" +
+                                    " public single-argument constructor that takes a Bundle. (`%1$s`)",
+                            node.getQualifiedName());
+                    context.report(ISSUE, node, context.getLocation((UElement) node), message);
                 }
             }
-        }
-
-        if (constructors.length > 0 && !hasDefaultConstructor && !hasBundleConstructor) {
-            String message = String.format(
-                    "This Controller needs to have either a public default constructor or a" +
-                            " public single-argument constructor that takes a Bundle. (`%1$s`)",
-                    declaration.getQualifiedName());
-            context.report(ISSUE, declaration, context.getLocation(declaration), message);
-        }
+        };
     }
+
 }

conductor-lint/src/main/java/com/bluelinelabs/conductor/lint/IssueRegistry.java

@@ -1,14 +0,0 @@
-package com.bluelinelabs.conductor.lint;
-
-import com.android.tools.lint.detector.api.Issue;
-
-import java.util.Arrays;
-import java.util.List;
-
-public final class IssueRegistry extends com.android.tools.lint.client.api.IssueRegistry {
-    @Override public List<Issue> getIssues() {
-        return Arrays.asList(
-                ControllerIssueDetector.ISSUE,
-                ControllerChangeHandlerIssueDetector.ISSUE);
-    }
-}

conductor-lint/src/main/java/com/bluelinelabs/conductor/lint/IssueRegistry.kt

@@ -0,0 +1,24 @@
+package com.bluelinelabs.conductor.lint
+
+import com.android.tools.lint.client.api.Vendor
+import com.android.tools.lint.detector.api.CURRENT_API
+import com.android.tools.lint.client.api.IssueRegistry as LintIssueRegistry
+
+@Suppress("UnstableApiUsage", "unused")
+class IssueRegistry : LintIssueRegistry() {
+
+  override val issues = listOf(
+    ControllerIssueDetector.ISSUE,
+    ControllerChangeHandlerIssueDetector.ISSUE
+  )
+
+  override val api: Int = CURRENT_API
+
+  private val githubIssueLink = "https://github.com/bluelinelabs/Conductor/issues/new"
+
+  override val vendor = Vendor(
+    vendorName = "Conductor",
+    feedbackUrl = githubIssueLink,
+    contact = githubIssueLink
+  )
+}

conductor-lint/src/test/java/com/bluelinelabs/conductor/lint/ControllerChangeHandlerDetectorTest.java

@@ -1,96 +1,137 @@
 package com.bluelinelabs.conductor.lint;
 
-import com.android.tools.lint.checks.infrastructure.LintDetectorTest;
-import com.android.tools.lint.detector.api.Detector;
-import com.android.tools.lint.detector.api.Issue;
+import static com.android.tools.lint.checks.infrastructure.TestFiles.java;
+import static com.android.tools.lint.checks.infrastructure.TestLintTask.lint;
+
+import com.android.tools.lint.checks.infrastructure.TestFile;
 
 import org.intellij.lang.annotations.Language;
+import org.junit.Test;
 
-import java.util.Collections;
-import java.util.List;
+@SuppressWarnings("UnstableApiUsage")
+public class ControllerChangeHandlerDetectorTest {
 
-import static com.google.common.truth.Truth.assertThat;
-
-public class ControllerChangeHandlerDetectorTest extends LintDetectorTest {
-
-    private static final String NO_WARNINGS = "No warnings.";
     private static final String CONSTRUCTOR =
             "src/test/SampleHandler.java:2: Error: This ControllerChangeHandler needs to have a public default constructor (test.SampleHandler) [ValidControllerChangeHandler]\n"
-            + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
-            + "^\n"
-            + "1 errors, 0 warnings\n";
-    private static final String PRIVATE_CLASS_ERROR =
-            "src/test/SampleHandler.java:2: Error: This ControllerChangeHandler class should be public (test.SampleHandler) [ValidControllerChangeHandler]\n"
-                    + "private class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
+                    + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                     + "^\n"
                     + "1 errors, 0 warnings\n";
 
-    public void testWithNoConstructor() throws Exception {
+    private final TestFile controllerChangeHandlerStub = java(
+            "package com.bluelinelabs.conductor;\n"
+                    + "abstract class ControllerChangeHandler {}"
+    );
+
+    @Test
+    public void testWithNoConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithEmptyConstructor() throws Exception {
+    @Test
+    public void testWithEmptyConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "    public SampleHandler() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithInvalidConstructor() throws Exception {
+    @Test
+    public void testWithInvalidConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "    public SampleHandler(int number) { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(CONSTRUCTOR);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(CONSTRUCTOR);
     }
 
-    public void testWithEmptyAndInvalidConstructor() throws Exception {
+    @Test
+    public void testWithEmptyAndInvalidConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "    public SampleHandler() { }\n"
                 + "    public SampleHandler(int number) { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithPrivateConstructor() throws Exception {
+    @Test
+    public void testWithPrivateConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "    private SampleHandler() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(CONSTRUCTOR);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(CONSTRUCTOR);
     }
 
-    public void testWithPrivateClass() throws Exception {
+    @Test
+    public void testWithPrivateClass() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "private class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
                 + "    public SampleHandler() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(PRIVATE_CLASS_ERROR);
+
+        lint()
+                .files(controllerChangeHandlerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect("src/test/SampleHandler.java:2: Error: This ControllerChangeHandler class should be public (test.SampleHandler) [ValidControllerChangeHandler]\n"
+                        + "private class SampleHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {\n"
+                        + "^\n"
+                        + "1 errors, 0 warnings\n");
     }
 
-    @Override
-    protected Detector getDetector() {
-        return new ControllerChangeHandlerIssueDetector();
-    }
+    @Test
+    public void testWithPrivateClassOfBaseClass() {
+        @Language("JAVA") String baseClass = ""
+                + "package test;\n"
+                + "abstract class BaseChangeHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {}";
 
-    @Override
-    protected List<Issue> getIssues() {
-        return Collections.singletonList(ControllerChangeHandlerIssueDetector.ISSUE);
-    }
+        @Language("JAVA") String source = ""
+                + "package test;\n"
+                + "private class SampleHandler extends test.BaseChangeHandler {}";
 
-    @Override
-    protected boolean allowCompilationErrors() {
-        return true;
+        lint()
+                .files(controllerChangeHandlerStub, java(baseClass), java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect("src/test/SampleHandler.java:2: Error: This ControllerChangeHandler class should be public (test.SampleHandler) [ValidControllerChangeHandler]\n" +
+                        "private class SampleHandler extends test.BaseChangeHandler {}\n" +
+                        "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\n" +
+                        "1 errors, 0 warnings");
     }
 }

conductor-lint/src/test/java/com/bluelinelabs/conductor/lint/ControllerDetectorTest.java

@@ -1,96 +1,147 @@
 package com.bluelinelabs.conductor.lint;
 
-import com.android.tools.lint.checks.infrastructure.LintDetectorTest;
-import com.android.tools.lint.detector.api.Detector;
-import com.android.tools.lint.detector.api.Issue;
+import static com.android.tools.lint.checks.infrastructure.TestFiles.java;
+import static com.android.tools.lint.checks.infrastructure.TestLintTask.lint;
+
+import com.android.tools.lint.checks.infrastructure.TestFile;
 
 import org.intellij.lang.annotations.Language;
+import org.junit.Test;
 
-import java.util.Collections;
-import java.util.List;
+@SuppressWarnings("UnstableApiUsage")
+public class ControllerDetectorTest {
 
-import static com.google.common.truth.Truth.assertThat;
-
-public class ControllerDetectorTest extends LintDetectorTest {
-
-    private static final String NO_WARNINGS = "No warnings.";
     private static final String CONSTRUCTOR_ERROR =
             "src/test/SampleController.java:2: Error: This Controller needs to have either a public default constructor or a public single-argument constructor that takes a Bundle. (test.SampleController) [ValidController]\n"
-            + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
-            + "^\n"
-            + "1 errors, 0 warnings\n";
+                    + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
+                    + "^\n"
+                    + "1 errors, 0 warnings\n";
     private static final String CLASS_ERROR =
             "src/test/SampleController.java:2: Error: This Controller class should be public (test.SampleController) [ValidController]\n"
                     + "private class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                     + "^\n"
                     + "1 errors, 0 warnings\n";
 
-    public void testWithNoConstructor() throws Exception {
+    private final TestFile controllerStub = java(
+            "package com.bluelinelabs.conductor;\n"
+                    + "abstract class Controller {}"
+    );
+
+
+    @Test
+    public void testWithNoConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithEmptyConstructor() throws Exception {
+    @Test
+    public void testWithEmptyConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "    public SampleController() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithInvalidConstructor() throws Exception {
+    @Test
+    public void testWithInvalidConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "    public SampleController(int number) { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(CONSTRUCTOR_ERROR);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(CONSTRUCTOR_ERROR);
     }
 
-    public void testWithEmptyAndInvalidConstructor() throws Exception {
+    @Test
+    public void testWithEmptyAndInvalidConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "    public SampleController() { }\n"
                 + "    public SampleController(int number) { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(NO_WARNINGS);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expectClean();
     }
 
-    public void testWithPrivateConstructor() throws Exception {
+    @Test
+    public void testWithBaseClassAndPrivateConstructor() {
+        @Language("JAVA")
+        String baseClass = ""
+                + "package test;\n"
+                + "public class BaseController extends com.bluelinelabs.conductor.Controller {}";
+
+        @Language("JAVA")
+        String source = ""
+                + "package test;\n"
+                + "public class SampleController extends BaseController {\n"
+                + "    private SampleController() { }\n"
+                + "}";
+
+        lint()
+                .files(controllerStub, java(baseClass), java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(
+                        "src/test/SampleController.java:2: Error: This Controller needs to have either a public default constructor or a public single-argument constructor that takes a Bundle. (test.SampleController) [ValidController]\n" +
+                                "public class SampleController extends BaseController {\n" +
+                                "^\n" +
+                                "1 errors, 0 warnings"
+                );
+    }
+
+    @Test
+    public void testWithPrivateConstructor() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "public class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "    private SampleController() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(CONSTRUCTOR_ERROR);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(CONSTRUCTOR_ERROR);
     }
 
-    public void testWithPrivateClass() throws Exception {
+    @Test
+    public void testWithPrivateClass() {
         @Language("JAVA") String source = ""
                 + "package test;\n"
                 + "private class SampleController extends com.bluelinelabs.conductor.Controller {\n"
                 + "    public SampleController() { }\n"
                 + "}";
-        assertThat(lintProject(java(source))).isEqualTo(CLASS_ERROR);
+
+        lint()
+                .files(controllerStub, java(source))
+                .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
+                .run()
+                .expect(CLASS_ERROR);
     }
 
-    @Override
-    protected Detector getDetector() {
-        return new ControllerIssueDetector();
-    }
-
-    @Override
-    protected List<Issue> getIssues() {
-        return Collections.singletonList(ControllerIssueDetector.ISSUE);
-    }
-
-    @Override
-    protected boolean allowCompilationErrors() {
-        return true;
-    }
 }

conductor-modules/androidx-transition/build.gradle

@@ -0,0 +1,31 @@
+plugins {
+    id("com.android.library")
+    alias(libs.plugins.mvnpublish)
+}
+
+android {
+    compileSdk libs.versions.compilesdk.get() as Integer
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+
+    defaultConfig {
+        minSdkVersion libs.versions.minsdk.get()
+        targetSdkVersion libs.versions.targetsdk.get()
+        versionCode Integer.parseInt(project.VERSION_CODE)
+        versionName project.VERSION_NAME
+    }
+
+    namespace "com.bluelinelabs.conductor.androidxtransition"
+}
+
+dependencies {
+    implementation libs.androidx.appcompat
+    implementation libs.androidx.collection
+    api libs.androidx.transition
+    implementation project(':conductor')
+}
+
+ext.artifactId = 'conductor-androidx-transition'

conductor-modules/androidx-transition/gradle.properties

@@ -0,0 +1,3 @@
+POM_NAME=Conductor AndroidX Transition Extensions
+POM_ARTIFACT_ID=conductor-androidx-transition
+POM_PACKAGING=aar

conductor-modules/androidx-transition/src/main/java/com/bluelinelabs/conductor/changehandler/androidxtransition/SharedElementTransitionChangeHandler.java

@@ -0,0 +1,656 @@
+package com.bluelinelabs.conductor.changehandler.androidxtransition;
+
+import android.graphics.Rect;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.ViewTreeObserver;
+import android.view.ViewTreeObserver.OnPreDrawListener;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.collection.ArrayMap;
+import androidx.core.app.SharedElementCallback;
+import androidx.core.view.ViewCompat;
+import androidx.core.view.ViewGroupCompat;
+import androidx.transition.Transition;
+import androidx.transition.TransitionSet;
+
+import com.bluelinelabs.conductor.Controller;
+import com.bluelinelabs.conductor.ControllerChangeHandler;
+import com.bluelinelabs.conductor.internal.TransitionUtils;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A TransitionChangeHandler that facilitates using different Transitions for the entering view, the exiting view,
+ * and shared elements between the two.
+ * <p/>
+ * Note that this class uses the <b>androidx</b> {@link Transition}. If you're using Android's platform transitions,
+ * consider using the {@code SharedElementTransitionChangeHandler} provided by the {@code android-transitions} Conductor module.
+ */
+// Much of this class is based on FragmentTransition.java and FragmentTransitionCompat21.java from the Android support library
+public abstract class SharedElementTransitionChangeHandler extends TransitionChangeHandler {
+
+    // A map of from -> to names. Generally these will be the same.
+    @NonNull  final ArrayMap<String, String> sharedElementNames = new ArrayMap<>();
+
+    @NonNull  final List<String> waitForTransitionNames = new ArrayList<>();
+    @NonNull  final List<ViewParentPair> removedViews = new ArrayList<>();
+
+    @Nullable Transition exitTransition;
+    @Nullable Transition enterTransition;
+    @Nullable Transition sharedElementTransition;
+    @Nullable private SharedElementCallback exitTransitionCallback;
+    @Nullable private SharedElementCallback enterTransitionCallback;
+
+    @NonNull
+    @Override
+    protected final Transition getTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush) {
+        exitTransition = getExitTransition(container, from, to, isPush);
+        enterTransition = getEnterTransition(container, from, to, isPush);
+        sharedElementTransition = getSharedElementTransition(container, from, to, isPush);
+        exitTransitionCallback = getExitTransitionCallback(container, from, to, isPush);
+        enterTransitionCallback = getEnterTransitionCallback(container, from, to, isPush);
+
+        if (enterTransition == null && sharedElementTransition == null && exitTransition == null) {
+            throw new IllegalStateException("SharedElementTransitionChangeHandler must have at least one transaction.");
+        }
+
+        return mergeTransitions(isPush);
+    }
+
+    @Override
+    public void prepareForTransition(@NonNull final ViewGroup container, @Nullable final View from, @Nullable final View to, @NonNull final Transition transition, final boolean isPush, @NonNull final OnTransitionPreparedListener onTransitionPreparedListener) {
+        OnTransitionPreparedListener listener = new OnTransitionPreparedListener() {
+            @Override
+            public void onPrepared() {
+                configureTransition(container, from, to, transition, isPush);
+                onTransitionPreparedListener.onPrepared();
+            }
+        };
+
+        configureSharedElements(container, from, to, isPush);
+
+        if (to != null && to.getParent() == null && waitForTransitionNames.size() > 0) {
+            waitOnAllTransitionNames(to, listener);
+            container.addView(to);
+        } else {
+            listener.onPrepared();
+        }
+    }
+
+    @Override
+    public final void executePropertyChanges(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, @Nullable Transition transition, boolean isPush) {
+        if (to != null && removedViews.size() > 0) {
+            to.setVisibility(View.VISIBLE);
+
+            for (ViewParentPair removedView : removedViews) {
+                removedView.parent.addView(removedView.view);
+            }
+
+            removedViews.clear();
+        }
+
+        super.executePropertyChanges(container, from, to, transition, isPush);
+    }
+
+    @Override
+    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) {
+        super.onAbortPush(newHandler, newTop);
+
+        removedViews.clear();
+    }
+
+    void configureTransition(@NonNull final ViewGroup container, @Nullable View from, @Nullable View to, @NonNull final Transition transition, boolean isPush) {
+        final View nonExistentView = new View(container.getContext());
+
+        List<View> fromSharedElements = new ArrayList<>();
+        List<View> toSharedElements = new ArrayList<>();
+
+        configureSharedElements(container, nonExistentView, to, from, isPush, fromSharedElements, toSharedElements);
+
+        List<View> exitingViews = exitTransition != null ? configureEnteringExitingViews(exitTransition, from, fromSharedElements, nonExistentView) : null;
+        if (exitingViews == null || exitingViews.isEmpty()) {
+            exitTransition = null;
+        }
+
+        if (enterTransition != null) {
+            enterTransition.addTarget(nonExistentView);
+        }
+
+        final List<View> enteringViews = new ArrayList<>();
+        scheduleRemoveTargets(transition, enterTransition, enteringViews, exitTransition, exitingViews, sharedElementTransition, toSharedElements);
+        scheduleTargetChange(container, to, nonExistentView, toSharedElements, enteringViews, exitingViews);
+
+        setNameOverrides(container, toSharedElements);
+        scheduleNameReset(container, toSharedElements);
+    }
+
+    private void waitOnAllTransitionNames(@NonNull final View to, @NonNull final OnTransitionPreparedListener onTransitionPreparedListener) {
+        OnPreDrawListener onPreDrawListener = new OnPreDrawListener() {
+            boolean addedSubviewListeners;
+
+            @Override
+            public boolean onPreDraw() {
+                List<View> foundViews = new ArrayList<>();
+                boolean allViewsFound = true;
+                for (String transitionName : waitForTransitionNames) {
+                    View namedView = TransitionUtils.findNamedView(to, transitionName);
+                    if (namedView != null) {
+                        foundViews.add(TransitionUtils.findNamedView(to, transitionName));
+                    } else {
+                        allViewsFound = false;
+                        break;
+                    }
+                }
+
+                if (allViewsFound && !addedSubviewListeners) {
+                    addedSubviewListeners = true;
+                    waitOnChildTransitionNames(to, foundViews, this, onTransitionPreparedListener);
+                }
+
+                return false;
+            }
+        };
+
+        to.getViewTreeObserver().addOnPreDrawListener(onPreDrawListener);
+    }
+
+    void waitOnChildTransitionNames(@NonNull final View to, @NonNull List<View> foundViews, @NonNull final OnPreDrawListener parentPreDrawListener, @NonNull final OnTransitionPreparedListener onTransitionPreparedListener) {
+        for (final View view : foundViews) {
+            OneShotPreDrawListener.add(true, view, new Runnable() {
+                @Override
+                public void run() {
+                    waitForTransitionNames.remove(ViewCompat.getTransitionName(view));
+
+                    removedViews.add(new ViewParentPair(view, (ViewGroup)view.getParent()));
+                    ((ViewGroup)view.getParent()).removeView(view);
+
+                    if (waitForTransitionNames.size() == 0) {
+                        to.getViewTreeObserver().removeOnPreDrawListener(parentPreDrawListener);
+                        to.setVisibility(View.INVISIBLE);
+                        onTransitionPreparedListener.onPrepared();
+                    }
+                }
+            });
+        }
+    }
+
+    private void scheduleTargetChange(@NonNull final ViewGroup container, @Nullable final View to, @NonNull final View nonExistentView,
+                                      @NonNull final List<View> toSharedElements, @NonNull final List<View> enteringViews, @Nullable final List<View> exitingViews) {
+        OneShotPreDrawListener.add(true, container, new Runnable() {
+            @Override
+            public void run() {
+                if (enterTransition != null) {
+                    enterTransition.removeTarget(nonExistentView);
+                    List<View> views = configureEnteringExitingViews(enterTransition, to, toSharedElements, nonExistentView);
+                    enteringViews.addAll(views);
+                }
+
+                if (exitingViews != null) {
+                    if (exitTransition != null) {
+                        List<View> tempExiting = new ArrayList<>();
+                        tempExiting.add(nonExistentView);
+                        TransitionUtils.replaceTargets(exitTransition, exitingViews, tempExiting);
+                    }
+                    exitingViews.clear();
+                    exitingViews.add(nonExistentView);
+                }
+            }
+        });
+    }
+
+    private Transition mergeTransitions(boolean isPush) {
+        boolean overlap = enterTransition == null || exitTransition == null || allowTransitionOverlap(isPush);
+
+        if (overlap) {
+            return TransitionUtils.mergeTransitions(TransitionSet.ORDERING_TOGETHER, exitTransition, enterTransition, sharedElementTransition);
+        } else {
+            Transition staggered = TransitionUtils.mergeTransitions(TransitionSet.ORDERING_SEQUENTIAL, exitTransition, enterTransition);
+            return TransitionUtils.mergeTransitions(TransitionSet.ORDERING_TOGETHER, staggered, sharedElementTransition);
+        }
+    }
+
+    @NonNull List<View> configureEnteringExitingViews(@NonNull Transition transition, @Nullable View view, @NonNull List<View> sharedElements, @NonNull View nonExistentView) {
+        List<View> viewList = new ArrayList<>();
+        if (view != null) {
+            captureTransitioningViews(viewList, view);
+        }
+        viewList.removeAll(sharedElements);
+        if (!viewList.isEmpty()) {
+            viewList.add(nonExistentView);
+            TransitionUtils.addTargets(transition, viewList);
+        }
+        return viewList;
+    }
+
+    private void configureSharedElements(@NonNull ViewGroup container, @NonNull final View nonExistentView, @Nullable final View to, @Nullable View from,
+                                         final boolean isPush, @NonNull final List<View> fromSharedElements, @NonNull final List<View> toSharedElements) {
+
+        if (to == null || from == null) {
+            return;
+        }
+
+        ArrayMap<String, View> capturedFromSharedElements = captureFromSharedElements(from);
+
+        if (sharedElementNames.isEmpty()) {
+            sharedElementTransition = null;
+        } else if (capturedFromSharedElements != null) {
+            fromSharedElements.addAll(capturedFromSharedElements.values());
+        }
+
+        if (enterTransition == null && exitTransition == null && sharedElementTransition == null) {
+            return;
+        }
+
+        callSharedElementStartEnd(capturedFromSharedElements, true);
+
+        final Rect toEpicenter;
+        if (sharedElementTransition != null) {
+            toEpicenter = new Rect();
+            TransitionUtils.setTargets(sharedElementTransition, nonExistentView, fromSharedElements);
+            setFromEpicenter(capturedFromSharedElements);
+            if (enterTransition != null) {
+                enterTransition.setEpicenterCallback(new Transition.EpicenterCallback() {
+                    @Override
+                    public Rect onGetEpicenter(Transition transition) {
+                        if (toEpicenter.isEmpty()) {
+                            return null;
+                        }
+                        return toEpicenter;
+                    }
+                });
+            }
+        } else {
+            toEpicenter = null;
+        }
+
+        OneShotPreDrawListener.add(true, container, new Runnable() {
+            @Override
+            public void run() {
+                ArrayMap<String, View> capturedToSharedElements = captureToSharedElements(to, isPush);
+
+                if (capturedToSharedElements != null) {
+                    toSharedElements.addAll(capturedToSharedElements.values());
+                    toSharedElements.add(nonExistentView);
+                }
+
+                callSharedElementStartEnd(capturedToSharedElements, false);
+                if (sharedElementTransition != null) {
+                    sharedElementTransition.getTargets().clear();
+                    sharedElementTransition.getTargets().addAll(toSharedElements);
+                    TransitionUtils.replaceTargets(sharedElementTransition, fromSharedElements, toSharedElements);
+
+                    final View toEpicenterView = getToEpicenterView(capturedToSharedElements);
+                    if (toEpicenterView != null && toEpicenter != null) {
+                        TransitionUtils.getBoundsOnScreen(toEpicenterView, toEpicenter);
+                    }
+                }
+            }
+        });
+    }
+
+    @Nullable View getToEpicenterView(@Nullable ArrayMap<String, View> toSharedElements) {
+        if (enterTransition != null && sharedElementNames.size() > 0 && toSharedElements != null) {
+            return toSharedElements.get(sharedElementNames.valueAt(0));
+        }
+        return null;
+    }
+
+    private void setFromEpicenter(@Nullable ArrayMap<String, View> fromSharedElements) {
+        if (sharedElementNames.size() > 0 && fromSharedElements != null) {
+            final View fromEpicenterView = fromSharedElements.get(sharedElementNames.keyAt(0));
+
+            if (sharedElementTransition != null) {
+                TransitionUtils.setEpicenter(sharedElementTransition, fromEpicenterView);
+            }
+
+            if (exitTransition != null) {
+                TransitionUtils.setEpicenter(exitTransition, fromEpicenterView);
+            }
+        }
+    }
+
+    @Nullable ArrayMap<String, View> captureToSharedElements(@Nullable final View to, boolean isPush) {
+        if (sharedElementNames.isEmpty() || sharedElementTransition == null || to == null) {
+            sharedElementNames.clear();
+            return null;
+        }
+
+        final ArrayMap<String, View> toSharedElements = new ArrayMap<>();
+        TransitionUtils.findNamedViews(toSharedElements, to);
+        for (ViewParentPair removedView : removedViews) {
+            toSharedElements.put(ViewCompat.getTransitionName(removedView.view), removedView.view);
+        }
+
+        final List<String> names = new ArrayList<>(sharedElementNames.values());
+
+        toSharedElements.retainAll(names);
+        if (enterTransitionCallback != null) {
+            enterTransitionCallback.onMapSharedElements(names, toSharedElements);
+            for (int i = names.size() - 1; i >= 0; i--) {
+                String name = names.get(i);
+                View view = toSharedElements.get(name);
+                if (view == null) {
+                    String key = findKeyForValue(sharedElementNames, name);
+                    if (key != null) {
+                        sharedElementNames.remove(key);
+                    }
+                } else if (!name.equals(ViewCompat.getTransitionName(view))) {
+                    String key = findKeyForValue(sharedElementNames, name);
+                    if (key != null) {
+                        sharedElementNames.put(key, ViewCompat.getTransitionName(view));
+                    }
+                }
+            }
+        } else {
+            for (int i = sharedElementNames.size() - 1; i >= 0; i--) {
+                final String targetName = sharedElementNames.valueAt(i);
+                if (!toSharedElements.containsKey(targetName)) {
+                    sharedElementNames.removeAt(i);
+                }
+            }
+        }
+        return toSharedElements;
+    }
+
+    @Nullable String findKeyForValue(@NonNull ArrayMap<String, String> map, @NonNull String value) {
+        final int numElements = map.size();
+        for (int i = 0; i < numElements; i++) {
+            if (value.equals(map.valueAt(i))) {
+                return map.keyAt(i);
+            }
+        }
+        return null;
+    }
+
+    @Nullable
+    private ArrayMap<String, View> captureFromSharedElements(@NonNull View from) {
+        if (sharedElementNames.isEmpty() || sharedElementTransition == null) {
+            sharedElementNames.clear();
+            return null;
+        }
+
+        final ArrayMap<String, View> fromSharedElements = new ArrayMap<>();
+        TransitionUtils.findNamedViews(fromSharedElements, from);
+
+        final List<String> names = new ArrayList<>(sharedElementNames.keySet());
+
+        fromSharedElements.retainAll(names);
+        if (exitTransitionCallback != null) {
+            exitTransitionCallback.onMapSharedElements(names, fromSharedElements);
+            for (int i = names.size() - 1; i >= 0; i--) {
+                String name = names.get(i);
+                View view = fromSharedElements.get(name);
+                if (view == null) {
+                    sharedElementNames.remove(name);
+                } else if (!name.equals(ViewCompat.getTransitionName(view))) {
+                    String targetValue = sharedElementNames.remove(name);
+                    sharedElementNames.put(ViewCompat.getTransitionName(view), targetValue);
+                }
+            }
+        } else {
+            sharedElementNames.retainAll(fromSharedElements.keySet());
+        }
+        return fromSharedElements;
+    }
+
+    void callSharedElementStartEnd(@Nullable ArrayMap<String, View> sharedElements, boolean isStart) {
+        if (enterTransitionCallback != null) {
+            final int count = sharedElements == null ? 0 : sharedElements.size();
+            List<View> views = new ArrayList<>(count);
+            List<String> names = new ArrayList<>(count);
+            for (int i = 0; i < count; i++) {
+                names.add(sharedElements.keyAt(i));
+                views.add(sharedElements.valueAt(i));
+            }
+            if (isStart) {
+                enterTransitionCallback.onSharedElementStart(names, views, null);
+            } else {
+                enterTransitionCallback.onSharedElementEnd(names, views, null);
+            }
+        }
+    }
+
+    private void captureTransitioningViews(@NonNull List<View> transitioningViews, @NonNull View view) {
+        if (view.getVisibility() == View.VISIBLE) {
+            if (view instanceof ViewGroup) {
+                ViewGroup viewGroup = (ViewGroup) view;
+                if (ViewGroupCompat.isTransitionGroup(viewGroup)) {
+                    transitioningViews.add(viewGroup);
+                } else {
+                    int count = viewGroup.getChildCount();
+                    for (int i = 0; i < count; i++) {
+                        View child = viewGroup.getChildAt(i);
+                        captureTransitioningViews(transitioningViews, child);
+                    }
+                }
+            } else {
+                transitioningViews.add(view);
+            }
+        }
+    }
+
+    private void scheduleRemoveTargets(@NonNull final Transition overallTransition,
+                                       @Nullable final Transition enterTransition, @Nullable final List<View> enteringViews,
+                                       @Nullable final Transition exitTransition, @Nullable final List<View> exitingViews,
+                                       @Nullable final Transition sharedElementTransition, @Nullable final List<View> toSharedElements) {
+        overallTransition.addListener(new Transition.TransitionListener() {
+            @Override
+            public void onTransitionStart(Transition transition) {
+                if (enterTransition != null && enteringViews != null) {
+                    TransitionUtils.replaceTargets(enterTransition, enteringViews, null);
+                }
+                if (exitTransition != null && exitingViews != null) {
+                    TransitionUtils.replaceTargets(exitTransition, exitingViews, null);
+                }
+                if (sharedElementTransition != null && toSharedElements != null) {
+                    TransitionUtils.replaceTargets(sharedElementTransition, toSharedElements, null);
+                }
+            }
+
+            @Override
+            public void onTransitionEnd(Transition transition) { }
+
+            @Override
+            public void onTransitionCancel(Transition transition) { }
+
+            @Override
+            public void onTransitionPause(Transition transition) { }
+
+            @Override
+            public void onTransitionResume(Transition transition) { }
+        });
+    }
+
+    private void setNameOverrides(@NonNull final View container, @NonNull final List<View> toSharedElements) {
+        OneShotPreDrawListener.add(true, container, new Runnable() {
+            @Override
+            public void run() {
+                final int numSharedElements = toSharedElements.size();
+                for (int i = 0; i < numSharedElements; i++) {
+                    View view = toSharedElements.get(i);
+                    String name = ViewCompat.getTransitionName(view);
+                    if (name != null) {
+                        String inName = findKeyForValue(sharedElementNames, name);
+                        ViewCompat.setTransitionName(view, inName);
+                    }
+                }
+            }
+        });
+    }
+
+    private void scheduleNameReset(@NonNull final ViewGroup container, @NonNull final List<View> toSharedElements) {
+        OneShotPreDrawListener.add(true, container, new Runnable() {
+            @Override
+            public void run() {
+                final int numSharedElements = toSharedElements.size();
+                for (int i = 0; i < numSharedElements; i++) {
+                    final View view = toSharedElements.get(i);
+                    final String name = ViewCompat.getTransitionName(view);
+                    final String inName = sharedElementNames.get(name);
+                    ViewCompat.setTransitionName(view, inName);
+                }
+            }
+        });
+    }
+
+    /**
+     * Will be called when views are ready to have their shared elements configured. Within this method one of the addSharedElement methods
+     * should be called for each shared element that will be used. If one or more of these shared elements will not instantly be available in
+     * the incoming view (for ex, in a RecyclerView), waitOnSharedElementNamed can be called to delay the transition until everything is available.
+     */
+    public abstract void configureSharedElements(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush);
+
+    /**
+     * Should return the transition that will be used on the exiting ("from") view, if one is desired.
+     */
+    @Nullable
+    public abstract Transition getExitTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush);
+
+    /**
+     * Should return the transition that will be used on shared elements between the from and to views.
+     */
+    @Nullable
+    public abstract Transition getSharedElementTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush);
+
+    /**
+     * Should return the transition that will be used on the entering ("to") view, if one is desired.
+     */
+    @Nullable
+    public abstract Transition getEnterTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush);
+
+    /**
+     * Should return a callback that can be used to customize transition behavior of the shared element transition for the "from" view.
+     */
+    @Nullable
+    public SharedElementCallback getExitTransitionCallback(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush) {
+        return null;
+    }
+
+    /**
+     * Should return a callback that can be used to customize transition behavior of the shared element transition for the "to" view.
+     */
+    @Nullable
+    public SharedElementCallback getEnterTransitionCallback(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush) {
+        return null;
+    }
+
+    /**
+     * Should return whether or not the the exit transition and enter transition should overlap. If true,
+     * the enter transition will start as soon as possible. Otherwise, the enter transition will wait until the
+     * completion of the exit transition. Defaults to true.
+     */
+    public boolean allowTransitionOverlap(boolean isPush) {
+        return true;
+    }
+
+    /**
+     * Used to register an element that will take part in the shared element transition.
+     *
+     * @param name The transition name that is used for both the entering and exiting views.
+     */
+    protected final void addSharedElement(@NonNull String name) {
+        sharedElementNames.put(name, name);
+    }
+
+    /**
+     * Used to register an element that will take part in the shared element transition. Maps the name used in the
+     * "from" view to the name used in the "to" view if they are not the same.
+     *
+     * @param fromName The transition name used in the "from" view
+     * @param toName The transition name used in the "to" view
+     */
+    protected final void addSharedElement(@NonNull String fromName, @NonNull String toName) {
+        sharedElementNames.put(fromName, toName);
+    }
+
+    /**
+     * Used to register an element that will take part in the shared element transition. Maps the name used in the
+     * "from" view to the name used in the "to" view if they are not the same.
+     *
+     * @param sharedElement The view from the "from" view that will take part in the shared element transition
+     * @param toName The transition name used in the "to" view
+     */
+    protected final void addSharedElement(@NonNull View sharedElement, @NonNull String toName) {
+        String transitionName = ViewCompat.getTransitionName(sharedElement);
+        if (transitionName == null) {
+            throw new IllegalArgumentException("Unique transitionNames are required for all sharedElements");
+        }
+        sharedElementNames.put(transitionName, toName);
+    }
+
+    /**
+     * The transition will be delayed until the view with the name passed in is available in the "to" hierarchy. This is
+     * particularly useful for views that don't load instantly, like RecyclerViews. Note that using this method can
+     * potentially lock up your app indefinitely if the view never loads!
+     */
+    protected final void waitOnSharedElementNamed(@NonNull String name) {
+        if (!sharedElementNames.values().contains(name)) {
+            throw new IllegalStateException("Can't wait on a shared element that hasn't been registered using addSharedElement");
+        }
+        waitForTransitionNames.add(name);
+    }
+
+    private static class OneShotPreDrawListener implements OnPreDrawListener, View.OnAttachStateChangeListener {
+
+        private final View view;
+        private ViewTreeObserver viewTreeObserver;
+        private final Runnable runnable;
+        private final boolean preDrawReturnValue;
+
+        private OneShotPreDrawListener(boolean preDrawReturnValue, @NonNull View view, @NonNull Runnable runnable) {
+            this.preDrawReturnValue = preDrawReturnValue;
+            this.view = view;
+            viewTreeObserver = view.getViewTreeObserver();
+            this.runnable = runnable;
+        }
+
+        @NonNull
+        public static OneShotPreDrawListener add(boolean preDrawReturnValue, @NonNull View view, @NonNull Runnable runnable) {
+            OneShotPreDrawListener listener = new OneShotPreDrawListener(preDrawReturnValue, view, runnable);
+            view.getViewTreeObserver().addOnPreDrawListener(listener);
+            view.addOnAttachStateChangeListener(listener);
+            return listener;
+        }
+
+        @Override
+        public boolean onPreDraw() {
+            removeListener();
+            runnable.run();
+            return preDrawReturnValue;
+        }
+
+        private void removeListener() {
+            if (viewTreeObserver.isAlive()) {
+                viewTreeObserver.removeOnPreDrawListener(this);
+            } else {
+                view.getViewTreeObserver().removeOnPreDrawListener(this);
+            }
+            view.removeOnAttachStateChangeListener(this);
+        }
+
+        @Override
+        public void onViewAttachedToWindow(View v) {
+            viewTreeObserver = v.getViewTreeObserver();
+        }
+
+        @Override
+        public void onViewDetachedFromWindow(View v) {
+            removeListener();
+        }
+
+    }
+
+    private static class ViewParentPair {
+        @NonNull final View view;
+        @NonNull final ViewGroup parent;
+
+        ViewParentPair(@NonNull View view, ViewGroup parent) {
+            this.view = view;
+            this.parent = parent;
+        }
+    }
+
+}

conductor-modules/androidx-transition/src/main/java/com/bluelinelabs/conductor/changehandler/androidxtransition/TransitionChangeHandler.java

@@ -1,29 +1,29 @@
-package com.bluelinelabs.conductor.changehandler;
+package com.bluelinelabs.conductor.changehandler.androidxtransition;
 
-import android.annotation.TargetApi;
-import android.os.Build;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.transition.Transition;
-import android.transition.Transition.TransitionListener;
-import android.transition.TransitionManager;
 import android.view.View;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.transition.Transition;
+import androidx.transition.TransitionManager;
+
 import com.bluelinelabs.conductor.Controller;
 import com.bluelinelabs.conductor.ControllerChangeHandler;
 
 /**
- * A base {@link ControllerChangeHandler} that facilitates using {@link android.transition.Transition}s to replace Controller Views.
+ * A base {@link ControllerChangeHandler} that facilitates using {@link Transition}s to replace Controller Views.
+ * <p/>
+ * Note that this class uses the <b>androidx</b> {@link Transition}. If you're using Android's platform transitions,
+ * consider using the {@code TransitionChangeHandler} provided by the {@code android-transitions} Conductor module.
  */
-@TargetApi(Build.VERSION_CODES.LOLLIPOP)
 public abstract class TransitionChangeHandler extends ControllerChangeHandler {
 
     public interface OnTransitionPreparedListener {
         void onPrepared();
     }
 
-    private boolean canceled;
+    boolean canceled;
     private boolean needsImmediateCompletion;
 
     /**
@@ -51,8 +51,12 @@ public abstract class TransitionChangeHandler extends ControllerChangeHandler {
         needsImmediateCompletion = true;
     }
 
+    @Nullable
+    private ControllerChangeCompletedListener listener;
+
     @Override
     public void performChange(@NonNull final ViewGroup container, @Nullable final View from, @Nullable final View to, final boolean isPush, @NonNull final ControllerChangeCompletedListener changeListener) {
+        listener = changeListener;
         if (canceled) {
             changeListener.onChangeCompleted();
             return;
@@ -63,19 +67,30 @@ public abstract class TransitionChangeHandler extends ControllerChangeHandler {
             return;
         }
 
-        final Transition transition = getTransition(container, from, to, isPush);
-        transition.addListener(new TransitionListener() {
+        final Runnable onTransitionNotStarted = new Runnable() {
             @Override
-            public void onTransitionStart(Transition transition) { }
+            public void run() {
+                changeListener.onChangeCompleted();
+            }
+        };
+
+        final Transition transition = getTransition(container, from, to, isPush);
+        transition.addListener(new Transition.TransitionListener() {
+            @Override
+            public void onTransitionStart(Transition transition) {
+                container.removeCallbacks(onTransitionNotStarted);
+            }
 
             @Override
             public void onTransitionEnd(Transition transition) {
-                changeListener.onChangeCompleted();
+                listener.onChangeCompleted();
+                listener = null;
             }
 
             @Override
             public void onTransitionCancel(Transition transition) {
-                changeListener.onChangeCompleted();
+                listener.onChangeCompleted();
+                listener = null;
             }
 
             @Override
@@ -91,13 +106,14 @@ public abstract class TransitionChangeHandler extends ControllerChangeHandler {
                 if (!canceled) {
                     TransitionManager.beginDelayedTransition(container, transition);
                     executePropertyChanges(container, from, to, transition, isPush);
+                    container.post(onTransitionNotStarted);
                 }
             }
         });
     }
 
     @Override
-    public boolean removesFromViewOnPush() {
+    public boolean getRemovesFromViewOnPush() {
         return true;
     }
 
@@ -126,7 +142,7 @@ public abstract class TransitionChangeHandler extends ControllerChangeHandler {
      * @param isPush     True if this is a push transaction, false if it's a pop
      */
     public void executePropertyChanges(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, @Nullable Transition transition, boolean isPush) {
-        if (from != null && (removesFromViewOnPush() || !isPush) && from.getParent() == container) {
+        if (from != null && (getRemovesFromViewOnPush() || !isPush) && from.getParent() == container) {
             container.removeView(from);
         }
         if (to != null && to.getParent() == null) {

conductor-modules/androidx-transition/src/main/java/com/bluelinelabs/conductor/internal/TransitionUtils.java

@@ -0,0 +1,184 @@
+package com.bluelinelabs.conductor.internal;
+
+import android.graphics.Rect;
+import android.view.View;
+import android.view.ViewGroup;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.core.view.ViewCompat;
+import androidx.transition.Transition;
+import androidx.transition.TransitionSet;
+
+import java.util.List;
+import java.util.Map;
+
+public class TransitionUtils {
+
+    public static void findNamedViews(@NonNull Map<String, View> namedViews, View view) {
+        if (view.getVisibility() == View.VISIBLE) {
+            String transitionName = ViewCompat.getTransitionName(view);
+            if (transitionName != null) {
+                namedViews.put(transitionName, view);
+            }
+
+            if (view instanceof ViewGroup) {
+                ViewGroup viewGroup = (ViewGroup) view;
+                int childCount = viewGroup.getChildCount();
+                for (int i = 0; i < childCount; i++) {
+                    View child = viewGroup.getChildAt(i);
+                    findNamedViews(namedViews, child);
+                }
+            }
+        }
+    }
+
+    @Nullable
+    public static View findNamedView(@NonNull View view, @NonNull String transitionName) {
+        if (transitionName.equals(ViewCompat.getTransitionName(view))) {
+            return view;
+        }
+
+        if (view instanceof ViewGroup) {
+            ViewGroup viewGroup = (ViewGroup) view;
+            int childCount = viewGroup.getChildCount();
+            for (int i = 0; i < childCount; i++) {
+                View viewWithTransitionName = findNamedView(viewGroup.getChildAt(i), transitionName);
+                if (viewWithTransitionName != null) {
+                    return viewWithTransitionName;
+                }
+            }
+        }
+
+        return null;
+    }
+
+    public static void setEpicenter(@NonNull Transition transition, @Nullable View view) {
+        if (view != null) {
+            final Rect epicenter = new Rect();
+            getBoundsOnScreen(view, epicenter);
+            transition.setEpicenterCallback(new Transition.EpicenterCallback() {
+                @Override
+                public Rect onGetEpicenter(Transition transition) {
+                    return epicenter;
+                }
+            });
+        }
+    }
+
+    public static void getBoundsOnScreen(@NonNull View view, @NonNull Rect epicenter) {
+        int[] loc = new int[2];
+        view.getLocationOnScreen(loc);
+        epicenter.set(loc[0], loc[1], loc[0] + view.getWidth(), loc[1] + view.getHeight());
+    }
+
+    public static void setTargets(@NonNull Transition transition, @NonNull View nonExistentView, @NonNull List<View> sharedViews) {
+        final List<View> views = transition.getTargets();
+        views.clear();
+        final int count = sharedViews.size();
+        for (int i = 0; i < count; i++) {
+            final View view = sharedViews.get(i);
+            bfsAddViewChildren(views, view);
+        }
+        views.add(nonExistentView);
+        sharedViews.add(nonExistentView);
+        addTargets(transition, sharedViews);
+    }
+
+    public static void addTargets(@Nullable Transition transition, @NonNull List<View> views) {
+        if (transition == null) {
+            return;
+        }
+        if (transition instanceof TransitionSet) {
+            TransitionSet set = (TransitionSet) transition;
+            int numTransitions = set.getTransitionCount();
+            for (int i = 0; i < numTransitions; i++) {
+                Transition child = set.getTransitionAt(i);
+                addTargets(child, views);
+            }
+        } else if (!hasSimpleTarget(transition)) {
+            List<View> targets = transition.getTargets();
+            if (isNullOrEmpty(targets)) {
+                int numViews = views.size();
+                for (int i = 0; i < numViews; i++) {
+                    transition.addTarget(views.get(i));
+                }
+            }
+        }
+    }
+
+    public static void replaceTargets(@NonNull Transition transition, @NonNull List<View> oldTargets, @Nullable List<View> newTargets) {
+        if (transition instanceof TransitionSet) {
+            TransitionSet set = (TransitionSet) transition;
+            int numTransitions = set.getTransitionCount();
+            for (int i = 0; i < numTransitions; i++) {
+                Transition child = set.getTransitionAt(i);
+                replaceTargets(child, oldTargets, newTargets);
+            }
+        } else if (!TransitionUtils.hasSimpleTarget(transition)) {
+            List<View> targets = transition.getTargets();
+            if (targets != null && targets.size() == oldTargets.size() && targets.containsAll(oldTargets)) {
+                final int targetCount = newTargets == null ? 0 : newTargets.size();
+                for (int i = 0; i < targetCount; i++) {
+                    transition.addTarget(newTargets.get(i));
+                }
+                for (int i = oldTargets.size() - 1; i >= 0; i--) {
+                    transition.removeTarget(oldTargets.get(i));
+                }
+            }
+        }
+    }
+
+    private static void bfsAddViewChildren(@NonNull final List<View> views, @NonNull final View startView) {
+        final int startIndex = views.size();
+        if (containedBeforeIndex(views, startView, startIndex)) {
+            return; // This child is already in the list, so all its children are also.
+        }
+        views.add(startView);
+        for (int index = startIndex; index < views.size(); index++) {
+            final View view = views.get(index);
+            if (view instanceof ViewGroup) {
+                ViewGroup viewGroup = (ViewGroup) view;
+                final int childCount = viewGroup.getChildCount();
+                for (int childIndex = 0; childIndex < childCount; childIndex++) {
+                    final View child = viewGroup.getChildAt(childIndex);
+                    if (!containedBeforeIndex(views, child, startIndex)) {
+                        views.add(child);
+                    }
+                }
+            }
+        }
+    }
+
+    private static boolean containedBeforeIndex(@NonNull List<View> views, View view, int maxIndex) {
+        for (int i = 0; i < maxIndex; i++) {
+            if (views.get(i) == view) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public static boolean hasSimpleTarget(@NonNull Transition transition) {
+        return !isNullOrEmpty(transition.getTargetIds())
+                || !isNullOrEmpty(transition.getTargetNames())
+                || !isNullOrEmpty(transition.getTargetTypes());
+    }
+
+    private static boolean isNullOrEmpty(@Nullable List list) {
+        return list == null || list.isEmpty();
+    }
+
+    @NonNull
+    public static TransitionSet mergeTransitions(int ordering, Transition... transitions) {
+        TransitionSet transitionSet = new TransitionSet();
+        for (Transition transition : transitions) {
+            if (transition != null) {
+                transitionSet.addTransition(transition);
+            }
+        }
+        transitionSet.setOrdering(ordering);
+        return transitionSet;
+    }
+
+}

conductor-modules/arch-components-lifecycle/build.gradle

@@ -1,29 +0,0 @@
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')
-
-apply plugin: 'com.android.library'
-
-android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
-    }
-
-    defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode Integer.parseInt(project.VERSION_CODE)
-        versionName project.VERSION_NAME
-    }
-}
-
-dependencies {
-    compile rootProject.ext.archComopnentsLifecycle
-
-    compile project(':conductor')
-}
-
-ext.artifactId = 'conductor-arch-components-lifecycle'

conductor-modules/arch-components-lifecycle/gradle.properties

@@ -1,4 +0,0 @@
-POM_NAME=Conductor Architecture Components Lifecycle Extensions
-POM_ARTIFACT_ID=conductor-archlifecycle
-POM_PACKAGING=aar
-VERSION_NAME=0.1.2-SNAPSHOT

conductor-modules/arch-components-lifecycle/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor.archlifecycle">
-    <application />
-</manifest>

conductor-modules/arch-components-lifecycle/src/main/java/com/bluelinelabs/conductor/archlifecycle/ControllerLifecycleRegistryOwner.java

@@ -1,79 +0,0 @@
-package com.bluelinelabs.conductor.archlifecycle;
-
-import android.arch.lifecycle.Lifecycle.Event;
-import android.arch.lifecycle.Lifecycle.State;
-import android.arch.lifecycle.LifecycleRegistry;
-import android.arch.lifecycle.LifecycleRegistryOwner;
-import android.support.annotation.NonNull;
-import android.view.View;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.Controller.LifecycleListener;
-
-public class ControllerLifecycleRegistryOwner extends LifecycleListener implements LifecycleRegistryOwner {
-
-    private final LifecycleRegistry lifecycleRegistry = new LifecycleRegistry(this);
-
-    public ControllerLifecycleRegistryOwner(Controller controller) {
-        lifecycleRegistry.handleLifecycleEvent(Event.ON_CREATE);
-        lifecycleRegistry.markState(State.CREATED);
-
-        controller.addLifecycleListener(new LifecycleListener() {
-            @Override
-            public void preCreateView(@NonNull Controller controller) {
-                lifecycleRegistry.handleLifecycleEvent(Event.ON_START);
-            }
-
-            @Override
-            public void postCreateView(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.markState(State.STARTED);
-            }
-
-            @Override
-            public void preAttach(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.handleLifecycleEvent(Event.ON_RESUME);
-            }
-
-            @Override
-            public void postAttach(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.markState(State.RESUMED);
-            }
-
-            @Override
-            public void preDetach(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.handleLifecycleEvent(Event.ON_PAUSE);
-            }
-
-            @Override
-            public void postDetach(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.markState(State.STARTED);
-            }
-
-            @Override
-            public void preDestroyView(@NonNull Controller controller, @NonNull View view) {
-                lifecycleRegistry.handleLifecycleEvent(Event.ON_STOP);
-            }
-
-            @Override
-            public void postDestroyView(@NonNull Controller controller) {
-                lifecycleRegistry.markState(State.CREATED);
-            }
-
-            @Override
-            public void preDestroy(@NonNull Controller controller) {
-                lifecycleRegistry.handleLifecycleEvent(Event.ON_DESTROY);
-            }
-
-            @Override
-            public void postDestroy(@NonNull Controller controller) {
-                lifecycleRegistry.markState(State.DESTROYED);
-            }
-        });
-    }
-
-    @Override
-    public LifecycleRegistry getLifecycle() {
-        return lifecycleRegistry;
-    }
-
-}

conductor-modules/arch-components-lifecycle/src/main/java/com/bluelinelabs/conductor/archlifecycle/LifecycleController.java

@@ -1,17 +0,0 @@
-package com.bluelinelabs.conductor.archlifecycle;
-
-import android.arch.lifecycle.LifecycleRegistry;
-import android.arch.lifecycle.LifecycleRegistryOwner;
-
-import com.bluelinelabs.conductor.Controller;
-
-public abstract class LifecycleController extends Controller implements LifecycleRegistryOwner {
-
-    private final ControllerLifecycleRegistryOwner lifecycleRegistryOwner = new ControllerLifecycleRegistryOwner(this);
-
-    @Override
-    public LifecycleRegistry getLifecycle() {
-        return lifecycleRegistryOwner.getLifecycle();
-    }
-
-}

conductor-modules/arch-components-lifecycle/src/main/java/com/bluelinelabs/conductor/archlifecycle/LifecycleRestoreViewOnCreateController.java

@@ -1,17 +0,0 @@
-package com.bluelinelabs.conductor.archlifecycle;
-
-import android.arch.lifecycle.LifecycleRegistry;
-import android.arch.lifecycle.LifecycleRegistryOwner;
-
-import com.bluelinelabs.conductor.RestoreViewOnCreateController;
-
-public abstract class LifecycleRestoreViewOnCreateController extends RestoreViewOnCreateController implements LifecycleRegistryOwner {
-
-    private final ControllerLifecycleRegistryOwner lifecycleRegistryOwner = new ControllerLifecycleRegistryOwner(this);
-
-    @Override
-    public LifecycleRegistry getLifecycle() {
-        return lifecycleRegistryOwner.getLifecycle();
-    }
-
-}

conductor-modules/autodispose/build.gradle

@@ -1,30 +0,0 @@
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')
-
-apply plugin: 'com.android.library'
-
-android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
-    }
-
-    defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode Integer.parseInt(project.VERSION_CODE)
-        versionName project.VERSION_NAME
-    }
-}
-
-dependencies {
-    compile rootProject.ext.rxJava2
-    compile rootProject.ext.autodispose
-
-    compile project(':conductor')
-}
-
-ext.artifactId = 'conductor-autodispose'

conductor-modules/autodispose/gradle.properties

@@ -1,3 +0,0 @@
-POM_NAME=Conductor AutoDispose Extensions
-POM_ARTIFACT_ID=conductor-autodispose
-POM_PACKAGING=aar

conductor-modules/autodispose/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor.autodispose">
-    <application />
-</manifest>

conductor-modules/autodispose/src/main/java/com/bluelinelabs/conductor/autodispose/ControllerEvent.java

@@ -1,14 +0,0 @@
-package com.bluelinelabs.conductor.autodispose;
-
-public enum ControllerEvent {
-
-    CREATE,
-    CONTEXT_AVAILABLE,
-    CREATE_VIEW,
-    ATTACH,
-    DETACH,
-    DESTROY_VIEW,
-    CONTEXT_UNAVAILABLE,
-    DESTROY
-
-}

conductor-modules/autodispose/src/main/java/com/bluelinelabs/conductor/autodispose/ControllerLifecycleSubjectHelper.java

@@ -1,71 +0,0 @@
-package com.bluelinelabs.conductor.autodispose;
-
-import android.content.Context;
-import android.support.annotation.NonNull;
-import android.view.View;
-
-import com.bluelinelabs.conductor.Controller;
-import com.uber.autodispose.OutsideLifecycleException;
-
-import io.reactivex.subjects.BehaviorSubject;
-
-public class ControllerLifecycleSubjectHelper {
-    private ControllerLifecycleSubjectHelper() { }
-
-    @NonNull
-    public static BehaviorSubject<ControllerEvent> create(Controller controller) {
-        ControllerEvent initialState;
-        if (controller.isBeingDestroyed() || controller.isDestroyed()) {
-            throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-        } else if (controller.isAttached()) {
-            initialState = ControllerEvent.ATTACH;
-        } else if (controller.getView() != null) {
-            initialState = ControllerEvent.CREATE_VIEW;
-        } else if (controller.getActivity() != null) {
-            initialState = ControllerEvent.CONTEXT_AVAILABLE;
-        } else {
-            initialState = ControllerEvent.CREATE;
-        }
-
-        final BehaviorSubject<ControllerEvent> subject = BehaviorSubject.createDefault(initialState);
-
-        controller.addLifecycleListener(new Controller.LifecycleListener() {
-            @Override
-            public void preContextAvailable(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CONTEXT_AVAILABLE);
-            }
-
-            @Override
-            public void preCreateView(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CREATE_VIEW);
-            }
-
-            @Override
-            public void preAttach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.ATTACH);
-            }
-
-            @Override
-            public void preDetach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DETACH);
-            }
-
-            @Override
-            public void preDestroyView(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DESTROY_VIEW);
-            }
-
-            @Override
-            public void preContextUnavailable(@NonNull Controller controller, @NonNull Context context) {
-                subject.onNext(ControllerEvent.CONTEXT_UNAVAILABLE);
-            }
-
-            @Override
-            public void preDestroy(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.DESTROY);
-            }
-        });
-
-        return subject;
-    }
-}

conductor-modules/autodispose/src/main/java/com/bluelinelabs/conductor/autodispose/ControllerScopeProvider.java

@@ -1,59 +0,0 @@
-package com.bluelinelabs.conductor.autodispose;
-
-import android.support.annotation.NonNull;
-
-import com.bluelinelabs.conductor.Controller;
-import com.uber.autodispose.LifecycleScopeProvider;
-import com.uber.autodispose.OutsideLifecycleException;
-
-import io.reactivex.Observable;
-import io.reactivex.functions.Function;
-import io.reactivex.subjects.BehaviorSubject;
-
-public class ControllerScopeProvider implements LifecycleScopeProvider<ControllerEvent> {
-    private static final Function<ControllerEvent, ControllerEvent> CORRESPONDING_EVENTS =
-            new Function<ControllerEvent, ControllerEvent>() {
-                @Override
-                public ControllerEvent apply(ControllerEvent lastEvent) throws Exception {
-                    switch (lastEvent) {
-                        case CREATE:
-                            return ControllerEvent.DESTROY;
-                        case CONTEXT_AVAILABLE:
-                            return ControllerEvent.CONTEXT_UNAVAILABLE;
-                        case CREATE_VIEW:
-                            return ControllerEvent.DESTROY_VIEW;
-                        case ATTACH:
-                            return ControllerEvent.DETACH;
-                        case DETACH:
-                            return ControllerEvent.DESTROY;
-                        default:
-                            throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-                    }
-                }
-            };
-
-    @NonNull private final BehaviorSubject<ControllerEvent> lifecycleSubject;
-
-    public static ControllerScopeProvider from(@NonNull Controller controller) {
-        return new ControllerScopeProvider(controller);
-    }
-
-    private ControllerScopeProvider(@NonNull Controller controller) {
-        lifecycleSubject = ControllerLifecycleSubjectHelper.create(controller);
-    }
-
-    @Override
-    public Observable<ControllerEvent> lifecycle() {
-        return lifecycleSubject.hide();
-    }
-
-    @Override
-    public Function<ControllerEvent, ControllerEvent> correspondingEvents() {
-        return CORRESPONDING_EVENTS;
-    }
-
-    @Override
-    public ControllerEvent peekLifecycle() {
-        return lifecycleSubject.getValue();
-    }
-}

conductor-modules/rxlifecycle/build.gradle

@@ -1,31 +0,0 @@
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')
-
-apply plugin: 'com.android.library'
-
-android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
-    }
-
-    defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode Integer.parseInt(project.VERSION_CODE)
-        versionName project.VERSION_NAME
-    }
-}
-
-dependencies {
-    compile rootProject.ext.rxJava
-    compile rootProject.ext.rxLifecycle
-    compile rootProject.ext.rxLifecycleAndroid
-
-    compile project(':conductor')
-}
-
-ext.artifactId = 'conductor-rxlifecycle'

conductor-modules/rxlifecycle/gradle.properties

@@ -1,3 +0,0 @@
-POM_NAME=Conductor RxLifecycle Extensions
-POM_ARTIFACT_ID=conductor-rxlifecycle
-POM_PACKAGING=aar

conductor-modules/rxlifecycle/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor.rxlifecycle">
-    <application />
-</manifest>

conductor-modules/rxlifecycle/src/main/java/com/bluelinelabs/conductor/rxlifecycle/ControllerEvent.java

@@ -1,14 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle;
-
-public enum ControllerEvent {
-
-    CREATE,
-    CONTEXT_AVAILABLE,
-    CREATE_VIEW,
-    ATTACH,
-    DETACH,
-    DESTROY_VIEW,
-    CONTEXT_UNAVAILABLE,
-    DESTROY
-
-}

conductor-modules/rxlifecycle/src/main/java/com/bluelinelabs/conductor/rxlifecycle/ControllerLifecycleSubjectHelper.java

@@ -1,77 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle;
-
-import android.content.Context;
-import android.support.annotation.NonNull;
-import android.view.View;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.Controller.LifecycleListener;
-import com.trello.rxlifecycle.OutsideLifecycleException;
-
-import rx.subjects.BehaviorSubject;
-
-/**
- * A simple utility class that will create a {@link BehaviorSubject} that calls onNext when events
- * occur in your {@link Controller}
- */
-public class ControllerLifecycleSubjectHelper {
-
-    private ControllerLifecycleSubjectHelper() { }
-
-    public static BehaviorSubject<ControllerEvent> create(Controller controller) {
-        ControllerEvent initialState;
-        if (controller.isBeingDestroyed() || controller.isDestroyed()) {
-            throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-        } else if (controller.isAttached()) {
-            initialState = ControllerEvent.ATTACH;
-        } else if (controller.getView() != null) {
-            initialState = ControllerEvent.CREATE_VIEW;
-        } else if (controller.getActivity() != null) {
-            initialState = ControllerEvent.CONTEXT_AVAILABLE;
-        } else {
-            initialState = ControllerEvent.CREATE;
-        }
-
-        final BehaviorSubject<ControllerEvent> subject = BehaviorSubject.create(initialState);
-
-        controller.addLifecycleListener(new LifecycleListener() {
-            @Override
-            public void preContextAvailable(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CONTEXT_AVAILABLE);
-            }
-
-            @Override
-            public void preCreateView(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CREATE_VIEW);
-            }
-
-            @Override
-            public void preAttach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.ATTACH);
-            }
-
-            @Override
-            public void preDetach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DETACH);
-            }
-
-            @Override
-            public void preDestroyView(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DESTROY_VIEW);
-            }
-
-            @Override
-            public void preContextUnavailable(@NonNull Controller controller, @NonNull Context context) {
-                subject.onNext(ControllerEvent.CONTEXT_UNAVAILABLE);
-            }
-
-            @Override
-            public void preDestroy(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.DESTROY);
-            }
-        });
-
-        return subject;
-    }
-
-}

conductor-modules/rxlifecycle/src/main/java/com/bluelinelabs/conductor/rxlifecycle/RxController.java

@@ -1,52 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle;
-
-import android.os.Bundle;
-import android.support.annotation.CheckResult;
-import android.support.annotation.NonNull;
-
-import com.bluelinelabs.conductor.Controller;
-import com.trello.rxlifecycle.LifecycleProvider;
-import com.trello.rxlifecycle.LifecycleTransformer;
-import com.trello.rxlifecycle.RxLifecycle;
-
-import rx.Observable;
-import rx.subjects.BehaviorSubject;
-
-/**
- * A base {@link Controller} that can be used to expose lifecycle events using RxJava
- */
-public abstract class RxController extends Controller implements LifecycleProvider<ControllerEvent> {
-
-    private final BehaviorSubject<ControllerEvent> lifecycleSubject;
-
-    public RxController() {
-        this(null);
-    }
-
-    public RxController(Bundle args) {
-        super(args);
-        lifecycleSubject = ControllerLifecycleSubjectHelper.create(this);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final Observable<ControllerEvent> lifecycle() {
-        return lifecycleSubject.asObservable();
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindUntilEvent(@NonNull ControllerEvent event) {
-        return RxLifecycle.bindUntilEvent(lifecycleSubject, event);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindToLifecycle() {
-        return RxControllerLifecycle.bindController(lifecycleSubject);
-    }
-
-}

conductor-modules/rxlifecycle/src/main/java/com/bluelinelabs/conductor/rxlifecycle/RxControllerLifecycle.java

@@ -1,48 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle;
-
-import android.support.annotation.CheckResult;
-import android.support.annotation.NonNull;
-
-import com.trello.rxlifecycle.LifecycleTransformer;
-import com.trello.rxlifecycle.OutsideLifecycleException;
-import com.trello.rxlifecycle.RxLifecycle;
-
-import rx.Observable;
-import rx.functions.Func1;
-
-public class RxControllerLifecycle {
-
-    /**
-     * Binds the given source to a Controller lifecycle. This is the Controller version of
-     * {@link com.trello.rxlifecycle.android.RxLifecycleAndroid#bindFragment(Observable)}.
-     *
-     * @param lifecycle the lifecycle sequence of a Controller
-     * @return a reusable {@link rx.Observable.Transformer} that unsubscribes the source during the Controller lifecycle
-     */
-    @NonNull
-    @CheckResult
-    public static <T> LifecycleTransformer<T> bindController(@NonNull final Observable<ControllerEvent> lifecycle) {
-        return RxLifecycle.bind(lifecycle, CONTROLLER_LIFECYCLE);
-    }
-
-    private static final Func1<ControllerEvent, ControllerEvent> CONTROLLER_LIFECYCLE =
-            new Func1<ControllerEvent, ControllerEvent>() {
-                @Override
-                public ControllerEvent call(ControllerEvent lastEvent) {
-                    switch (lastEvent) {
-                        case CREATE:
-                            return ControllerEvent.DESTROY;
-                        case CONTEXT_AVAILABLE:
-                            return ControllerEvent.CONTEXT_UNAVAILABLE;
-                        case ATTACH:
-                            return ControllerEvent.DETACH;
-                        case CREATE_VIEW:
-                            return ControllerEvent.DESTROY_VIEW;
-                        case DETACH:
-                            return ControllerEvent.DESTROY;
-                        default:
-                            throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-                    }
-                }
-            };
-}

conductor-modules/rxlifecycle/src/main/java/com/bluelinelabs/conductor/rxlifecycle/RxRestoreViewOnCreateController.java

@@ -1,52 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle;
-
-import android.os.Bundle;
-import android.support.annotation.CheckResult;
-import android.support.annotation.NonNull;
-
-import com.bluelinelabs.conductor.RestoreViewOnCreateController;
-import com.trello.rxlifecycle.LifecycleProvider;
-import com.trello.rxlifecycle.LifecycleTransformer;
-import com.trello.rxlifecycle.RxLifecycle;
-
-import rx.Observable;
-import rx.subjects.BehaviorSubject;
-
-/**
- * A base {@link RestoreViewOnCreateController} that can be used to expose lifecycle events using RxJava
- */
-public abstract class RxRestoreViewOnCreateController extends RestoreViewOnCreateController implements LifecycleProvider<ControllerEvent> {
-
-    private final BehaviorSubject<ControllerEvent> lifecycleSubject;
-
-    public RxRestoreViewOnCreateController() {
-        this(null);
-    }
-
-    public RxRestoreViewOnCreateController(Bundle args) {
-        super(args);
-        lifecycleSubject = ControllerLifecycleSubjectHelper.create(this);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final Observable<ControllerEvent> lifecycle() {
-        return lifecycleSubject.asObservable();
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindUntilEvent(@NonNull ControllerEvent event) {
-        return RxLifecycle.bindUntilEvent(lifecycleSubject, event);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindToLifecycle() {
-        return RxControllerLifecycle.bindController(lifecycleSubject);
-    }
-
-}

conductor-modules/rxlifecycle2/build.gradle

@@ -1,31 +0,0 @@
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')
-
-apply plugin: 'com.android.library'
-
-android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
-    }
-
-    defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode Integer.parseInt(project.VERSION_CODE)
-        versionName project.VERSION_NAME
-    }
-}
-
-dependencies {
-    compile rootProject.ext.rxJava2
-    compile rootProject.ext.rxLifecycle2
-    compile rootProject.ext.rxLifecycleAndroid2
-
-    compile project(':conductor')
-}
-
-ext.artifactId = 'conductor-rxlifecycle2'

conductor-modules/rxlifecycle2/gradle.properties

@@ -1,3 +0,0 @@
-POM_NAME=Conductor RxLifecycle2 Extensions
-POM_ARTIFACT_ID=conductor-rxlifecycle2
-POM_PACKAGING=aar

conductor-modules/rxlifecycle2/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor.rxlifecycle2">
-    <application />
-</manifest>

conductor-modules/rxlifecycle2/src/main/java/com/bluelinelabs/conductor/rxlifecycle2/ControllerEvent.java

@@ -1,14 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle2;
-
-public enum ControllerEvent {
-
-    CREATE,
-    CONTEXT_AVAILABLE,
-    CREATE_VIEW,
-    ATTACH,
-    DETACH,
-    DESTROY_VIEW,
-    CONTEXT_UNAVAILABLE,
-    DESTROY
-
-}

conductor-modules/rxlifecycle2/src/main/java/com/bluelinelabs/conductor/rxlifecycle2/ControllerLifecycleSubjectHelper.java

@@ -1,71 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle2;
-
-import android.content.Context;
-import android.support.annotation.NonNull;
-import android.view.View;
-
-import com.bluelinelabs.conductor.Controller;
-import com.trello.rxlifecycle2.OutsideLifecycleException;
-
-import io.reactivex.subjects.BehaviorSubject;
-
-public class ControllerLifecycleSubjectHelper {
-    private ControllerLifecycleSubjectHelper() {
-    }
-
-    public static BehaviorSubject<ControllerEvent> create(Controller controller) {
-        ControllerEvent initialState;
-        if (controller.isBeingDestroyed() || controller.isDestroyed()) {
-            throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-        } else if (controller.isAttached()) {
-            initialState = ControllerEvent.ATTACH;
-        } else if (controller.getView() != null) {
-            initialState = ControllerEvent.CREATE_VIEW;
-        } else if (controller.getActivity() != null) {
-            initialState = ControllerEvent.CONTEXT_AVAILABLE;
-        } else {
-            initialState = ControllerEvent.CREATE;
-        }
-
-        final BehaviorSubject<ControllerEvent> subject = BehaviorSubject.createDefault(initialState);
-
-        controller.addLifecycleListener(new Controller.LifecycleListener() {
-            @Override
-            public void preContextAvailable(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CONTEXT_AVAILABLE);
-            }
-
-            @Override
-            public void preCreateView(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.CREATE_VIEW);
-            }
-
-            @Override
-            public void preAttach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.ATTACH);
-            }
-
-            @Override
-            public void preDetach(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DETACH);
-            }
-
-            @Override
-            public void preDestroyView(@NonNull Controller controller, @NonNull View view) {
-                subject.onNext(ControllerEvent.DESTROY_VIEW);
-            }
-
-            @Override
-            public void preContextUnavailable(@NonNull Controller controller, @NonNull Context context) {
-                subject.onNext(ControllerEvent.CONTEXT_UNAVAILABLE);
-            }
-
-            @Override
-            public void preDestroy(@NonNull Controller controller) {
-                subject.onNext(ControllerEvent.DESTROY);
-            }
-        });
-
-        return subject;
-    }
-}

conductor-modules/rxlifecycle2/src/main/java/com/bluelinelabs/conductor/rxlifecycle2/RxController.java

@@ -1,49 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle2;
-
-import android.os.Bundle;
-import android.support.annotation.CheckResult;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import com.bluelinelabs.conductor.Controller;
-import com.trello.rxlifecycle2.LifecycleProvider;
-import com.trello.rxlifecycle2.LifecycleTransformer;
-import com.trello.rxlifecycle2.RxLifecycle;
-import io.reactivex.Observable;
-import io.reactivex.subjects.BehaviorSubject;
-
-/**
- * A base {@link Controller} that can be used to expose lifecycle events using RxJava
- */
-public abstract class RxController extends Controller implements LifecycleProvider<ControllerEvent> {
-    private final BehaviorSubject<ControllerEvent> lifecycleSubject;
-
-    public RxController(){
-        this(null);
-    }
-
-    public RxController(@Nullable Bundle args) {
-        super(args);
-        lifecycleSubject = ControllerLifecycleSubjectHelper.create(this);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final Observable<ControllerEvent> lifecycle() {
-        return lifecycleSubject.hide();
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindUntilEvent(@NonNull ControllerEvent event) {
-        return RxLifecycle.bindUntilEvent(lifecycleSubject, event);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindToLifecycle() {
-        return RxControllerLifecycle.bindController(lifecycleSubject);
-    }
-}

conductor-modules/rxlifecycle2/src/main/java/com/bluelinelabs/conductor/rxlifecycle2/RxControllerLifecycle.java

@@ -1,43 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle2;
-
-import android.support.annotation.NonNull;
-import com.trello.rxlifecycle2.LifecycleTransformer;
-import com.trello.rxlifecycle2.OutsideLifecycleException;
-import com.trello.rxlifecycle2.RxLifecycle;
-import io.reactivex.Observable;
-import io.reactivex.functions.Function;
-
-public class RxControllerLifecycle {
-
-    /**
-     * Binds the given source to a Controller lifecycle. This is the Controller version of
-     * {@link com.trello.rxlifecycle2.android.RxLifecycleAndroid#bindFragment(Observable)}.
-     *
-     * @param lifecycle the lifecycle sequence of a Controller
-     * @return a reusable {@link io.reactivex.ObservableTransformer} that unsubscribes the source during the Controller lifecycle
-     */
-    public static <T> LifecycleTransformer<T> bindController(@NonNull final Observable<ControllerEvent> lifecycle) {
-        return RxLifecycle.bind(lifecycle, CONTROLLER_LIFECYCLE);
-    }
-
-    private static final Function<ControllerEvent, ControllerEvent> CONTROLLER_LIFECYCLE =
-        new Function<ControllerEvent, ControllerEvent>() {
-            @Override
-            public ControllerEvent apply(ControllerEvent lastEvent) {
-                switch (lastEvent) {
-                    case CREATE:
-                        return ControllerEvent.DESTROY;
-                    case CONTEXT_AVAILABLE:
-                        return ControllerEvent.CONTEXT_UNAVAILABLE;
-                    case ATTACH:
-                        return ControllerEvent.DETACH;
-                    case CREATE_VIEW:
-                        return ControllerEvent.DESTROY_VIEW;
-                    case DETACH:
-                        return ControllerEvent.DESTROY;
-                    default:
-                        throw new OutsideLifecycleException("Cannot bind to Controller lifecycle when outside of it.");
-                }
-            }
-        };
-}

conductor-modules/rxlifecycle2/src/main/java/com/bluelinelabs/conductor/rxlifecycle2/RxRestoreViewOnCreateController.java

@@ -1,45 +0,0 @@
-package com.bluelinelabs.conductor.rxlifecycle2;
-
-import android.os.Bundle;
-import android.support.annotation.CheckResult;
-import android.support.annotation.NonNull;
-import com.bluelinelabs.conductor.RestoreViewOnCreateController;
-import com.trello.rxlifecycle2.LifecycleProvider;
-import com.trello.rxlifecycle2.LifecycleTransformer;
-import com.trello.rxlifecycle2.RxLifecycle;
-import io.reactivex.Observable;
-import io.reactivex.subjects.BehaviorSubject;
-
-public abstract class RxRestoreViewOnCreateController extends RestoreViewOnCreateController implements LifecycleProvider<ControllerEvent> {
-    private final BehaviorSubject<ControllerEvent> lifecycleSubject;
-
-    public RxRestoreViewOnCreateController() {
-        this(null);
-    }
-
-    public RxRestoreViewOnCreateController(Bundle args) {
-        super(args);
-        lifecycleSubject = ControllerLifecycleSubjectHelper.create(this);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final Observable<ControllerEvent> lifecycle() {
-        return lifecycleSubject.hide();
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindUntilEvent(@NonNull ControllerEvent event) {
-        return RxLifecycle.bindUntilEvent(lifecycleSubject, event);
-    }
-
-    @Override
-    @NonNull
-    @CheckResult
-    public final <T> LifecycleTransformer<T> bindToLifecycle() {
-        return RxControllerLifecycle.bindController(lifecycleSubject);
-    }
-}

conductor-modules/support/build.gradle

@@ -1,48 +0,0 @@
-buildscript {
-    repositories {
-        jcenter()
-    }
-    dependencies {
-        classpath 'de.mobilej.unmock:UnMockPlugin:0.6.0'
-    }
-}
-
-apply plugin: 'com.android.library'
-apply plugin: 'de.mobilej.unmock'
-
-android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
-    }
-
-    defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
-        versionCode Integer.parseInt(project.VERSION_CODE)
-        versionName project.VERSION_NAME
-    }
-}
-
-dependencies {
-    testCompile rootProject.ext.junit
-    testCompile rootProject.ext.roboelectric
-
-    compile rootProject.ext.supportAppCompat
-    compile project(':conductor')
-
-    unmock 'org.robolectric:android-all:4.3_r2-robolectric-0'
-}
-
-unMock {
-    keep "android.os.Bundle"
-    keep "android.os.BaseBundle"
-}
-
-ext.artifactId = 'conductor-support'
-
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')

conductor-modules/support/gradle.properties

@@ -1,3 +0,0 @@
-POM_NAME=Conductor Support Extensions
-POM_ARTIFACT_ID=conductor-support
-POM_PACKAGING=aar

conductor-modules/support/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor.support">
-    <application />
-</manifest>

conductor-modules/support/src/main/java/com/bluelinelabs/conductor/support/ControllerPagerAdapter.java

@@ -1,154 +0,0 @@
-package com.bluelinelabs.conductor.support;
-
-import android.os.Bundle;
-import android.os.Parcelable;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.view.PagerAdapter;
-import android.util.SparseArray;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.Router;
-import com.bluelinelabs.conductor.RouterTransaction;
-
-/**
- * @deprecated Use RouterPagerAdapter instead! This implementation was too limited and had too many
- * gotchas associated with it.
- *
- * An adapter for ViewPagers that will handle adding and removing Controllers
- */
-@Deprecated
-public abstract class ControllerPagerAdapter extends PagerAdapter {
-
-    private static final String KEY_SAVED_PAGES = "ControllerPagerAdapter.savedStates";
-    private static final String KEY_SAVES_STATE = "ControllerPagerAdapter.savesState";
-    private static final String KEY_VISIBLE_PAGE_IDS_KEYS = "ControllerPagerAdapter.visiblePageIds.keys";
-    private static final String KEY_VISIBLE_PAGE_IDS_VALUES = "ControllerPagerAdapter.visiblePageIds.values";
-
-    private final Controller host;
-    private boolean savesState;
-    private SparseArray<Bundle> savedPages = new SparseArray<>();
-    private SparseArray<String> visiblePageIds = new SparseArray<>();
-
-    /**
-     * Creates a new ControllerPagerAdapter using the passed host.
-     */
-    public ControllerPagerAdapter(@NonNull Controller host, boolean saveControllerState) {
-        this.host = host;
-        savesState = saveControllerState;
-    }
-
-    /**
-     * Return the Controller associated with a specified position.
-     */
-    @NonNull
-    public abstract Controller getItem(int position);
-
-    @Override
-    public Object instantiateItem(ViewGroup container, int position) {
-        final String name = makeControllerName(container.getId(), getItemId(position));
-
-        Router router = host.getChildRouter(container, name);
-        if (savesState && !router.hasRootController()) {
-            Bundle routerSavedState = savedPages.get(position);
-
-            if (routerSavedState != null) {
-                router.restoreInstanceState(routerSavedState);
-            }
-        }
-
-        final Controller controller;
-        if (!router.hasRootController()) {
-            controller = getItem(position);
-            router.setRoot(RouterTransaction.with(controller).tag(name));
-        } else {
-            router.rebindIfNeeded();
-            controller = router.getControllerWithTag(name);
-        }
-
-        if (controller != null) {
-            visiblePageIds.put(position, controller.getInstanceId());
-        }
-
-        return router.getControllerWithTag(name);
-    }
-
-    @Override
-    public void destroyItem(ViewGroup container, int position, Object object) {
-        Router router = ((Controller)object).getRouter();
-
-        if (savesState) {
-            Bundle savedState = new Bundle();
-            router.saveInstanceState(savedState);
-            savedPages.put(position, savedState);
-        }
-
-        visiblePageIds.remove(position);
-
-        host.removeChildRouter(router);
-    }
-
-    @Override
-    public boolean isViewFromObject(View view, Object object) {
-        return ((Controller)object).getView() == view;
-    }
-
-    @Override
-    public Parcelable saveState() {
-        Bundle bundle = new Bundle();
-        bundle.putBoolean(KEY_SAVES_STATE, savesState);
-        bundle.putSparseParcelableArray(KEY_SAVED_PAGES, savedPages);
-
-        int[] visiblePageIdsKeys = new int[visiblePageIds.size()];
-        String[] visiblePageIdsValues = new String[visiblePageIds.size()];
-        for (int i = 0; i < visiblePageIds.size(); i++) {
-            visiblePageIdsKeys[i] = visiblePageIds.keyAt(i);
-            visiblePageIdsValues[i] = visiblePageIds.valueAt(i);
-        }
-        bundle.putIntArray(KEY_VISIBLE_PAGE_IDS_KEYS, visiblePageIdsKeys);
-        bundle.putStringArray(KEY_VISIBLE_PAGE_IDS_VALUES, visiblePageIdsValues);
-
-        return bundle;
-    }
-
-    @Override
-    public void restoreState(Parcelable state, ClassLoader loader) {
-        Bundle bundle = (Bundle)state;
-        if (state != null) {
-            savesState = bundle.getBoolean(KEY_SAVES_STATE, false);
-            savedPages = bundle.getSparseParcelableArray(KEY_SAVED_PAGES);
-
-            int[] visiblePageIdsKeys = bundle.getIntArray(KEY_VISIBLE_PAGE_IDS_KEYS);
-            String[] visiblePageIdsValues = bundle.getStringArray(KEY_VISIBLE_PAGE_IDS_VALUES);
-            visiblePageIds = new SparseArray<>(visiblePageIdsKeys.length);
-            for (int i = 0; i < visiblePageIdsKeys.length; i++) {
-                visiblePageIds.put(visiblePageIdsKeys[i], visiblePageIdsValues[i]);
-            }
-        }
-    }
-
-    /**
-     * Returns the already instantiated Controller in the specified position or {@code null} if
-     * this position does not yet have a controller.
-     */
-    @Nullable
-    public Controller getController(int position) {
-        String instanceId = visiblePageIds.get(position);
-        if (instanceId != null) {
-            return host.getRouter().getControllerWithInstanceId(instanceId);
-        } else {
-            return null;
-        }
-    }
-
-    public long getItemId(int position) {
-        return position;
-    }
-
-    private static String makeControllerName(int viewId, long id) {
-        return viewId + ":" + id;
-    }
-
-}

conductor-modules/support/src/test/java/com/bluelinelabs/conductor/support/StateSaveTests.java

@@ -1,113 +0,0 @@
-package com.bluelinelabs.conductor.support;
-
-import android.app.Activity;
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.util.SparseArray;
-import android.widget.FrameLayout;
-
-import com.bluelinelabs.conductor.Conductor;
-import com.bluelinelabs.conductor.Router;
-import com.bluelinelabs.conductor.RouterTransaction;
-import com.bluelinelabs.conductor.support.util.FakePager;
-import com.bluelinelabs.conductor.support.util.TestController;
-
-import org.junit.Before;
-import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.robolectric.Robolectric;
-import org.robolectric.RobolectricTestRunner;
-import org.robolectric.annotation.Config;
-import org.robolectric.util.ActivityController;
-
-import static org.junit.Assert.assertEquals;
-
-@RunWith(RobolectricTestRunner.class)
-@Config(manifest = Config.NONE)
-public class StateSaveTests {
-
-    private FakePager pager;
-    private RouterPagerAdapter pagerAdapter;
-
-    public void createActivityController(Bundle savedInstanceState) {
-        ActivityController<Activity> activityController = Robolectric.buildActivity(Activity.class).create().start().resume();
-        Router router = Conductor.attachRouter(activityController.get(), new FrameLayout(activityController.get()), savedInstanceState);
-        TestController controller = new TestController();
-        router.setRoot(RouterTransaction.with(controller));
-
-        pager = new FakePager(new FrameLayout(activityController.get()));
-        pager.setOffscreenPageLimit(1);
-
-        pagerAdapter = new RouterPagerAdapter(controller) {
-            @Override
-            public void configureRouter(@NonNull Router router, int position) {
-                if (!router.hasRootController()) {
-                    router.setRoot(RouterTransaction.with(new TestController()));
-                }
-            }
-
-            @Override
-            public int getCount() {
-                return 20;
-            }
-        };
-
-        pager.setAdapter(pagerAdapter);
-    }
-
-    @Before
-    public void setup() {
-        createActivityController(null);
-    }
-
-    @Test
-    public void testNoMaxSaves() {
-        // Load all pages
-        for (int i = 0; i < pagerAdapter.getCount(); i++) {
-            pager.pageTo(i);
-        }
-
-        pager.pageTo(pagerAdapter.getCount() / 2);
-
-        // Ensure all non-visible pages are saved
-        assertEquals(pagerAdapter.getCount() - 1 - pager.getOffscreenPageLimit() * 2, pagerAdapter.getSavedPages().size());
-    }
-
-    @Test
-    public void testMaxSavedSet() {
-        final int maxPages = 3;
-        pagerAdapter.setMaxPagesToStateSave(maxPages);
-
-        // Load all pages
-        for (int i = 0; i < pagerAdapter.getCount(); i++) {
-            pager.pageTo(i);
-        }
-
-        final int firstSelectedItem = pagerAdapter.getCount() / 2;
-        pager.pageTo(firstSelectedItem);
-
-        SparseArray<Bundle> savedPages = pagerAdapter.getSavedPages();
-
-        // Ensure correct number of pages are saved
-        assertEquals(maxPages, savedPages.size());
-
-        // Ensure correct pages are saved
-        assertEquals(pagerAdapter.getCount() - 3, savedPages.keyAt(0));
-        assertEquals(pagerAdapter.getCount() - 2, savedPages.keyAt(1));
-        assertEquals(pagerAdapter.getCount() - 1, savedPages.keyAt(2));
-
-        final int secondSelectedItem = 1;
-        pager.pageTo(secondSelectedItem);
-
-        savedPages = pagerAdapter.getSavedPages();
-
-        // Ensure correct number of pages are saved
-        assertEquals(maxPages, savedPages.size());
-
-        // Ensure correct pages are saved
-        assertEquals(firstSelectedItem - 1, savedPages.keyAt(0));
-        assertEquals(firstSelectedItem, savedPages.keyAt(1));
-        assertEquals(firstSelectedItem + 1, savedPages.keyAt(2));
-    }
-
-}

conductor-modules/support/src/test/java/com/bluelinelabs/conductor/support/util/FakePager.java

@@ -1,61 +0,0 @@
-package com.bluelinelabs.conductor.support.util;
-
-import android.util.SparseArray;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.support.RouterPagerAdapter;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public class FakePager {
-
-    private ViewGroup container;
-    private int offscreenPageLimit;
-    private final SparseArray<Object> pages = new SparseArray<>();
-
-    private RouterPagerAdapter adapter;
-
-    public FakePager(ViewGroup container) {
-        this.container = container;
-    }
-
-    public void setAdapter(RouterPagerAdapter adapter) {
-        this.adapter = adapter;
-    }
-
-    public void pageTo(int page) {
-        int firstPage = Math.max(0, page - offscreenPageLimit);
-        int lastPage = Math.min(adapter.getCount() - 1, page + offscreenPageLimit);
-
-        List<Integer> pagesI = new ArrayList<>();
-        for (int i = 0; i < pages.size(); i++) {
-            pagesI.add(pages.keyAt(i));
-        }
-
-        for (int i = pages.size() - 1; i >= 0; i--) {
-            int key = pages.keyAt(i);
-
-            if (key < firstPage || key > lastPage) {
-                adapter.destroyItem(container, key, pages.get(key));
-                pages.remove(key);
-            }
-        }
-
-        for (int key = firstPage; key <= lastPage; key++) {
-            if (pages.get(key) == null) {
-                pages.put(key, adapter.instantiateItem(container, key));
-            }
-        }
-
-        adapter.setPrimaryItem(container, page, pages.get(page));
-    }
-
-    public int getOffscreenPageLimit() {
-        return offscreenPageLimit;
-    }
-
-    public void setOffscreenPageLimit(int offscreenPageLimit) {
-        this.offscreenPageLimit = offscreenPageLimit;
-    }
-}

conductor-modules/viewpager/build.gradle

@@ -0,0 +1,37 @@
+plugins {
+    id("com.android.library")
+    id("kotlin-android")
+    alias(libs.plugins.mvnpublish)
+}
+
+android {
+    compileSdk libs.versions.compilesdk.get() as Integer
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+
+    kotlinOptions {
+        jvmTarget = "11"
+    }
+
+    defaultConfig {
+        minSdkVersion libs.versions.minsdk.get()
+        targetSdkVersion libs.versions.targetsdk.get()
+        versionCode Integer.parseInt(project.VERSION_CODE)
+        versionName project.VERSION_NAME
+    }
+
+    namespace "com.bluelinelabs.conductor.viewpager"
+}
+
+dependencies {
+    testImplementation libs.junit
+    testImplementation libs.robolectric
+
+    implementation libs.androidx.appcompat
+    implementation project(':conductor')
+}
+
+ext.artifactId = 'conductor-viewpager'

conductor-modules/viewpager/gradle.properties

@@ -0,0 +1,3 @@
+POM_NAME=Conductor PagerAdapter
+POM_ARTIFACT_ID=conductor-viewpager
+POM_PACKAGING=aar

conductor-modules/viewpager/src/main/java/com/bluelinelabs/conductor/viewpager/RouterPagerAdapter.java

@@ -1,35 +1,42 @@
-package com.bluelinelabs.conductor.support;
+package com.bluelinelabs.conductor.viewpager;
 
 import android.os.Bundle;
 import android.os.Parcelable;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.v4.view.PagerAdapter;
 import android.util.SparseArray;
 import android.view.View;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.viewpager.widget.PagerAdapter;
+
 import com.bluelinelabs.conductor.Controller;
 import com.bluelinelabs.conductor.Router;
 import com.bluelinelabs.conductor.RouterTransaction;
 
 import java.util.ArrayList;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 /**
- * An adapter for ViewPagers that uses Routers as pages
+ * An ViewPager adapter that uses Routers as pages
  */
 public abstract class RouterPagerAdapter extends PagerAdapter {
 
     private static final String KEY_SAVED_PAGES = "RouterPagerAdapter.savedStates";
+    private static final String KEY_TAGS_KEYS = "RouterPagerAdapter.tags.keys";
+    private static final String KEY_TAGS_VALUES = "RouterPagerAdapter.tags.values";
     private static final String KEY_MAX_PAGES_TO_STATE_SAVE = "RouterPagerAdapter.maxPagesToStateSave";
     private static final String KEY_SAVE_PAGE_HISTORY = "RouterPagerAdapter.savedPageHistory";
 
     private final Controller host;
     private int maxPagesToStateSave = Integer.MAX_VALUE;
+    private final Map<Integer, String> tags = new HashMap<>();
     private SparseArray<Bundle> savedPages = new SparseArray<>();
-    private SparseArray<Router> visibleRouters = new SparseArray<>();
+    private final SparseArray<Router> visibleRouters = new SparseArray<>();
     private ArrayList<Integer> savedPageHistory = new ArrayList<>();
+    private Router currentPrimaryRouter;
 
     /**
      * Creates a new RouterPagerAdapter using the passed host.
@@ -64,32 +71,47 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
     public Object instantiateItem(ViewGroup container, int position) {
         final String name = makeRouterName(container.getId(), getItemId(position));
 
-        Router router = host.getChildRouter(container, name);
+        // Ensure we don't try to restore state for a router with a different ID just because
+        // the position was reused. Fixes https://github.com/bluelinelabs/Conductor/issues/582
+        if (tags.get(position) != null && !tags.get(position).equals(name)) {
+            savedPages.remove(position);
+        }
+
+        Router router = host.getChildRouter(container, name)
+                .setPopRootControllerMode(Router.PopRootControllerMode.NEVER);
         if (!router.hasRootController()) {
             Bundle routerSavedState = savedPages.get(position);
 
             if (routerSavedState != null) {
                 router.restoreInstanceState(routerSavedState);
                 savedPages.remove(position);
+                savedPageHistory.remove((Integer) position);
             }
         }
 
         router.rebindIfNeeded();
         configureRouter(router, position);
 
+        if (router != currentPrimaryRouter) {
+            for (RouterTransaction transaction : router.getBackstack()) {
+                transaction.controller().setOptionsMenuHidden(true);
+            }
+        }
+
+        tags.put(position, name);
         visibleRouters.put(position, router);
         return router;
     }
 
     @Override
-    public void destroyItem(ViewGroup container, int position, Object object) {
+    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
         Router router = (Router)object;
 
         Bundle savedState = new Bundle();
         router.saveInstanceState(savedState);
         savedPages.put(position, savedState);
 
-        savedPageHistory.remove((Integer)position);
+        savedPageHistory.remove((Integer) position);
         savedPageHistory.add(position);
 
         ensurePagesSaved();
@@ -100,7 +122,25 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
     }
 
     @Override
-    public boolean isViewFromObject(View view, Object object) {
+    public void setPrimaryItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
+        Router router = (Router) object;
+        if (router != currentPrimaryRouter) {
+            if (currentPrimaryRouter != null) {
+                for (RouterTransaction transaction : currentPrimaryRouter.getBackstack()) {
+                    transaction.controller().setOptionsMenuHidden(true);
+                }
+            }
+            if (router != null) {
+                for (RouterTransaction transaction : router.getBackstack()) {
+                    transaction.controller().setOptionsMenuHidden(false);
+                }
+            }
+            currentPrimaryRouter = router;
+        }
+    }
+
+    @Override
+    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
         Router router = (Router)object;
         final List<RouterTransaction> backstack = router.getBackstack();
         for (RouterTransaction transaction : backstack) {
@@ -115,6 +155,8 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
     public Parcelable saveState() {
         Bundle bundle = new Bundle();
         bundle.putSparseParcelableArray(KEY_SAVED_PAGES, savedPages);
+        bundle.putIntegerArrayList(KEY_TAGS_KEYS, new ArrayList<>(tags.keySet()));
+        bundle.putStringArrayList(KEY_TAGS_VALUES, new ArrayList<>(tags.values()));
         bundle.putInt(KEY_MAX_PAGES_TO_STATE_SAVE, maxPagesToStateSave);
         bundle.putIntegerArrayList(KEY_SAVE_PAGE_HISTORY, savedPageHistory);
         return bundle;
@@ -127,6 +169,14 @@ public abstract class RouterPagerAdapter extends PagerAdapter {
             savedPages = bundle.getSparseParcelableArray(KEY_SAVED_PAGES);
             maxPagesToStateSave = bundle.getInt(KEY_MAX_PAGES_TO_STATE_SAVE);
             savedPageHistory = bundle.getIntegerArrayList(KEY_SAVE_PAGE_HISTORY);
+
+            List<Integer> tagsKeys = bundle.getIntegerArrayList(KEY_TAGS_KEYS);
+            List<String> tagsValues = bundle.getStringArrayList(KEY_TAGS_VALUES);
+            if (tagsKeys != null && tagsValues != null && tagsKeys.size() == tagsValues.size()) {
+                for (int i = 0; i < tagsKeys.size(); i++) {
+                    tags.put(tagsKeys.get(i), tagsValues.get(i));
+                }
+            }
         }
     }
 

conductor-modules/viewpager/src/test/java/com/bluelinelabs/conductor/viewpager/StateSaveTests.kt

@@ -0,0 +1,78 @@
+package com.bluelinelabs.conductor.viewpager
+
+import com.bluelinelabs.conductor.viewpager.util.TestActivity
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.Robolectric
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE)
+class StateSaveTests {
+
+  private val testController = Robolectric.buildActivity(TestActivity::class.java)
+    .setup()
+    .get()
+    .testController()
+
+  private val pagerAdapter = testController.pagerAdapter
+  private val pager = testController.pager
+  private val destroyedItems = testController.destroyedItems
+
+  @Test
+  fun testNoMaxSaves() {
+    // Load all pages
+    for (i in 0 until pagerAdapter.count) {
+      pager.currentItem = i
+    }
+
+    // Ensure all non-visible pages are saved
+    assertEquals(
+      destroyedItems.size,
+      pagerAdapter.savedPages.size()
+    )
+  }
+
+  @Test
+  fun testMaxSavedSet() {
+    val maxPages = 3
+    pagerAdapter.setMaxPagesToStateSave(maxPages)
+
+    // Load all pages
+    for (i in 0 until pagerAdapter.count) {
+      pager.currentItem = i
+    }
+
+    val firstSelectedItem = pagerAdapter.count / 2
+    for (i in pagerAdapter.count downTo firstSelectedItem) {
+      pager.currentItem = i
+    }
+
+    var savedPages = pagerAdapter.savedPages
+
+    // Ensure correct number of pages are saved
+    assertEquals(maxPages, savedPages.size())
+
+    // Ensure correct pages are saved
+    assertEquals(destroyedItems[destroyedItems.lastIndex], savedPages.keyAt(0))
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 1], savedPages.keyAt(1))
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 2], savedPages.keyAt(2))
+
+    val secondSelectedItem = 1
+    for (i in firstSelectedItem downTo secondSelectedItem) {
+      pager.currentItem = i
+    }
+
+    savedPages = pagerAdapter.savedPages
+
+    // Ensure correct number of pages are saved
+    assertEquals(maxPages, savedPages.size())
+
+    // Ensure correct pages are saved
+    assertEquals(destroyedItems[destroyedItems.lastIndex], savedPages.keyAt(0))
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 1], savedPages.keyAt(1))
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 2], savedPages.keyAt(2))
+  }
+}

conductor-modules/viewpager/src/test/java/com/bluelinelabs/conductor/viewpager/util/TestActivity.kt

@@ -0,0 +1,85 @@
+package com.bluelinelabs.conductor.viewpager.util
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.FrameLayout
+import androidx.core.view.ViewCompat
+import androidx.fragment.app.FragmentActivity
+import androidx.viewpager.widget.ViewPager
+import com.bluelinelabs.conductor.Conductor
+import com.bluelinelabs.conductor.Controller
+import com.bluelinelabs.conductor.Router
+import com.bluelinelabs.conductor.RouterTransaction
+import com.bluelinelabs.conductor.asTransaction
+import com.bluelinelabs.conductor.viewpager.RouterPagerAdapter
+
+class TestActivity : FragmentActivity() {
+
+  private lateinit var router: Router
+
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+
+    router = Conductor.attachRouter(
+      this,
+      findViewById(android.R.id.content),
+      savedInstanceState
+    )
+    if (!router.hasRootController()) {
+      router.setRoot(TestController().asTransaction())
+    }
+  }
+
+  fun testController(): TestController {
+    return router.backstack.single().controller as TestController
+  }
+}
+
+class TestController : Controller() {
+
+  val destroyedItems = mutableListOf<Int>()
+  lateinit var pagerAdapter: RouterPagerAdapter
+  lateinit var pager: ViewPager
+
+  override fun onCreateView(
+    inflater: LayoutInflater,
+    container: ViewGroup,
+    savedViewState: Bundle?
+  ): View {
+    pager = ViewPager(container.context).also {
+      it.id = ViewCompat.generateViewId()
+    }
+    pager.offscreenPageLimit = 1
+    pagerAdapter = object : RouterPagerAdapter(this) {
+
+      override fun configureRouter(router: Router, position: Int) {
+        if (!router.hasRootController()) {
+          router.setRoot(RouterTransaction.with(PageController()))
+        }
+      }
+
+      override fun getCount(): Int {
+        return 20
+      }
+
+      override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
+        super.destroyItem(container, position, `object`)
+        destroyedItems.add(position)
+      }
+    }
+    pager.adapter = pagerAdapter
+    return pager
+  }
+}
+
+class PageController : Controller() {
+  override fun onCreateView(
+    inflater: LayoutInflater,
+    container: ViewGroup,
+    savedViewState: Bundle?
+  ): View {
+    return FrameLayout(container.context)
+  }
+}

conductor-modules/viewpager2/build.gradle

@@ -0,0 +1,45 @@
+plugins {
+    id("com.android.library")
+    id("kotlin-android")
+    id("kotlin-parcelize")
+    alias(libs.plugins.mvnpublish)
+}
+
+android {
+    compileSdk libs.versions.compilesdk.get() as Integer
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+
+    kotlinOptions {
+        jvmTarget = "11"
+    }
+
+    defaultConfig {
+        minSdkVersion libs.versions.minsdk.get()
+        targetSdkVersion libs.versions.targetsdk.get()
+        versionCode Integer.parseInt(project.VERSION_CODE)
+        versionName project.VERSION_NAME
+    }
+
+    testOptions {
+        unitTests {
+            includeAndroidResources = true
+        }
+    }
+
+    namespace "com.bluelinelabs.conductor.viewpager2"
+}
+
+dependencies {
+    testImplementation libs.junit
+    testImplementation libs.robolectric
+
+    implementation libs.androidx.appcompat
+    implementation libs.androidx.viewpager2
+    implementation project(':conductor')
+}
+
+ext.artifactId = 'conductor-viewpager2'

conductor-modules/viewpager2/gradle.properties

@@ -0,0 +1,3 @@
+POM_NAME=Conductor ViewPager2 Adapter
+POM_ARTIFACT_ID=conductor-viewpager2
+POM_PACKAGING=aar

conductor-modules/viewpager2/src/main/java/com/bluelinelabs/conductor/viewpager2/RouterStateAdapter.kt

@@ -0,0 +1,256 @@
+package com.bluelinelabs.conductor.viewpager2
+
+import android.os.Bundle
+import android.os.Parcelable
+import android.util.LongSparseArray
+import android.util.SparseArray
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+import androidx.viewpager2.adapter.StatefulAdapter
+import androidx.viewpager2.widget.ViewPager2
+import com.bluelinelabs.conductor.Controller
+import com.bluelinelabs.conductor.Router
+import kotlinx.parcelize.Parcelize
+
+/**
+ * An ViewPager2 adapter that uses Routers as pages
+ */
+abstract class RouterStateAdapter(private val host: Controller) :
+  RecyclerView.Adapter<RouterViewHolder>(), StatefulAdapter {
+
+  private var savedPages = LongSparseArray<Bundle>()
+  internal var savedPageHistory = mutableListOf<Long>()
+  private var maxPagesToStateSave = Int.MAX_VALUE
+  private val visibleRouters = SparseArray<Router>()
+  private var currentPrimaryRouterPosition = 0
+  private var primaryItemCallback: PrimaryItemCallback? = null
+
+  init {
+    super.setHasStableIds(true)
+  }
+
+  /**
+   * Called when a router is instantiated. Here the router's root should be set if needed.
+   *
+   * @param router   The router used for the page
+   * @param position The page position to be instantiated.
+   */
+  abstract fun configureRouter(router: Router, position: Int)
+
+  /**
+   * Sets the maximum number of pages that will have their states saved. When this number is exceeded,
+   * the page that was state saved least recently will have its state removed from the save data.
+   */
+  open fun setMaxPagesToStateSave(maxPagesToStateSave: Int) {
+    require(maxPagesToStateSave >= 0) { "Only positive integers may be passed for maxPagesToStateSave." }
+    this.maxPagesToStateSave = maxPagesToStateSave
+    ensurePagesSaved()
+  }
+
+  private fun inferViewPager(recyclerView: RecyclerView): ViewPager2 {
+    return recyclerView.parent as? ViewPager2
+      ?: error("Expected ViewPager2 instance. Got: ${recyclerView.parent}")
+  }
+
+  override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
+    val viewPager = inferViewPager(recyclerView)
+    primaryItemCallback = PrimaryItemCallback().also {
+      viewPager.registerOnPageChangeCallback(it)
+    }
+  }
+
+  override fun onDetachedFromRecyclerView(recyclerView: RecyclerView) {
+    val viewPager = inferViewPager(recyclerView)
+    primaryItemCallback?.let {
+      viewPager.unregisterOnPageChangeCallback(it)
+    }
+    primaryItemCallback = null
+  }
+
+  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RouterViewHolder {
+    return RouterViewHolder(parent)
+  }
+
+  override fun onBindViewHolder(holder: RouterViewHolder, position: Int) {
+    holder.currentItemPosition = position
+
+    attachRouter(holder, position)
+  }
+
+  override fun onViewAttachedToWindow(holder: RouterViewHolder) {
+    super.onViewAttachedToWindow(holder)
+
+    if (!holder.attached) {
+      attachRouter(holder, holder.currentItemPosition)
+    }
+  }
+
+  override fun onViewDetachedFromWindow(holder: RouterViewHolder) {
+    super.onViewDetachedFromWindow(holder)
+
+    detachRouter(holder)
+
+    // Controller has fully detached and destroyed its view reference by now. Remove the leftover
+    // view from the container.
+    holder.container.removeAllViews()
+  }
+
+  override fun onViewRecycled(holder: RouterViewHolder) {
+    super.onViewRecycled(holder)
+
+    detachRouter(holder)
+
+    holder.currentRouter?.let { router ->
+      host.removeChildRouter(router)
+      holder.currentRouter = null
+    }
+  }
+
+  override fun onFailedToRecycleView(holder: RouterViewHolder): Boolean {
+    return true
+  }
+
+  override fun getItemId(position: Int): Long {
+    return position.toLong()
+  }
+
+  override fun setHasStableIds(hasStableIds: Boolean) {
+    throw UnsupportedOperationException("Stable Ids are required for the adapter to function properly")
+  }
+
+  override fun saveState(): Parcelable {
+    // Ensure all visible pages are saved, starting at the outermost pages and working our way in
+    val visiblePositions = (0 until visibleRouters.size())
+      .map { visibleRouters.keyAt(it) }.toMutableList()
+    while (visiblePositions.isNotEmpty()) {
+      val lastPosition = visiblePositions.removeAt(visiblePositions.lastIndex)
+      savePage(getItemId(lastPosition), visibleRouters[lastPosition])
+
+      if (visiblePositions.isNotEmpty()) {
+        val firstPosition = visiblePositions.removeAt(0)
+        savePage(getItemId(firstPosition), visibleRouters[firstPosition])
+      }
+    }
+
+    return SavedState(
+      savedPagesKeys = (0 until savedPages.size()).map { savedPages.keyAt(it) },
+      savedPagesValues = (0 until savedPages.size()).map { savedPages.valueAt(it) },
+      savedPageHistory = savedPageHistory,
+      maxPagesToStateSave = maxPagesToStateSave
+    )
+  }
+
+  override fun restoreState(state: Parcelable) {
+    if (state !is SavedState) return
+
+    savedPages = LongSparseArray()
+    state.savedPagesKeys.indices.forEach { index ->
+      savedPages.put(state.savedPagesKeys[index], state.savedPagesValues[index])
+    }
+
+    savedPageHistory = state.savedPageHistory.toMutableList()
+    maxPagesToStateSave = state.maxPagesToStateSave
+  }
+
+  private fun attachRouter(holder: RouterViewHolder, position: Int) {
+    val itemId = getItemId(position)
+    val router = host.getChildRouter(holder.container, "$itemId", true, false)!!
+            .setPopRootControllerMode(Router.PopRootControllerMode.NEVER)
+
+    // This should have already been handled by onViewRecycled, but it seems like this wasn't
+    // always reliably called
+    if (router != holder.currentRouter) {
+      holder.currentRouter?.let { host.removeChildRouter(it) }
+    }
+
+    holder.currentRouter = router
+    holder.currentItemId = itemId
+
+    if (!router.hasRootController()) {
+      val routerSavedState = savedPages[itemId]
+      if (routerSavedState != null) {
+        router.restoreInstanceState(routerSavedState)
+        savedPages.remove(itemId)
+        savedPageHistory.remove(itemId)
+      }
+    }
+
+    router.rebindIfNeeded()
+    configureRouter(router, position)
+
+    if (position != currentPrimaryRouterPosition) {
+      for (transaction in router.backstack) {
+        transaction.controller.setOptionsMenuHidden(true)
+      }
+    }
+
+    visibleRouters.put(position, router)
+
+    holder.attached = true
+  }
+
+  private fun detachRouter(holder: RouterViewHolder) {
+    if (!holder.attached) {
+      return
+    }
+
+    holder.currentRouter?.let { router ->
+      router.prepareForHostDetach()
+
+      savePage(holder.currentItemId, router)
+
+      if (visibleRouters[holder.currentItemPosition] == router) {
+        visibleRouters.remove(holder.currentItemPosition)
+      }
+    }
+
+    holder.attached = false
+  }
+
+  private fun savePage(itemId: Long, router: Router) {
+    val savedState = Bundle()
+    router.saveInstanceState(savedState)
+    savedPages.put(itemId, savedState)
+
+    savedPageHistory.remove(itemId)
+    savedPageHistory.add(itemId)
+
+    ensurePagesSaved()
+  }
+
+  private fun ensurePagesSaved() {
+    while (savedPages.size() > maxPagesToStateSave) {
+      val routerIdToRemove = savedPageHistory.removeAt(0)
+      savedPages.remove(routerIdToRemove)
+    }
+  }
+
+  /**
+   * Returns the already instantiated Router in the specified position or `null` if there
+   * is no router associated with this position.
+   */
+  fun getRouter(position: Int): Router? {
+    return visibleRouters[position]
+  }
+
+  inner class PrimaryItemCallback : ViewPager2.OnPageChangeCallback() {
+    override fun onPageSelected(position: Int) {
+      val router = visibleRouters[position]
+      if (position != currentPrimaryRouterPosition) {
+        val previousRouter = visibleRouters[currentPrimaryRouterPosition]
+
+        previousRouter?.backstack?.forEach { it.controller.setOptionsMenuHidden(true) }
+        router?.backstack?.forEach { it.controller.setOptionsMenuHidden(false) }
+        currentPrimaryRouterPosition = position
+      }
+    }
+  }
+
+  @Parcelize
+  private data class SavedState(
+    val savedPagesKeys: List<Long>,
+    val savedPagesValues: List<Bundle>,
+    val savedPageHistory: List<Long>,
+    val maxPagesToStateSave: Int
+  ) : Parcelable
+}

conductor-modules/viewpager2/src/main/java/com/bluelinelabs/conductor/viewpager2/RouterViewHolder.kt

@@ -0,0 +1,27 @@
+package com.bluelinelabs.conductor.viewpager2
+
+import android.view.ViewGroup
+import androidx.core.view.ViewCompat
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+import com.bluelinelabs.conductor.ChangeHandlerFrameLayout
+import com.bluelinelabs.conductor.Router
+
+class RouterViewHolder private constructor(val container: ChangeHandlerFrameLayout) : ViewHolder(container) {
+  var currentRouter: Router? = null
+  var currentItemPosition = 0
+  var currentItemId = 0L
+  var attached = false
+
+  companion object {
+    operator fun invoke(parent: ViewGroup): RouterViewHolder {
+      val container = ChangeHandlerFrameLayout(parent.context)
+      container.id = ViewCompat.generateViewId()
+      container.layoutParams = ViewGroup.LayoutParams(
+        ViewGroup.LayoutParams.MATCH_PARENT,
+        ViewGroup.LayoutParams.MATCH_PARENT
+      )
+      container.isSaveEnabled = false
+      return RouterViewHolder(container)
+    }
+  }
+}

conductor-modules/viewpager2/src/test/java/com/bluelinelabs/conductor/viewpager2/StateSaveTests.kt

@@ -0,0 +1,119 @@
+package com.bluelinelabs.conductor.viewpager2
+
+import android.os.Looper.getMainLooper
+import android.widget.FrameLayout
+import androidx.core.view.ViewCompat
+import androidx.fragment.app.FragmentActivity
+import androidx.viewpager2.widget.ViewPager2
+import com.bluelinelabs.conductor.Conductor
+import com.bluelinelabs.conductor.Router
+import com.bluelinelabs.conductor.RouterTransaction.Companion.with
+import com.bluelinelabs.conductor.viewpager2.util.TestController
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.Robolectric
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.Shadows.shadowOf
+import org.robolectric.annotation.Config
+
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE)
+class StateSaveTests {
+
+  private val pager: ViewPager2
+  private val adapter: RouterStateAdapter
+  private val destroyedItems = mutableListOf<Int>()
+
+  init {
+    val activityController = Robolectric.buildActivity(FragmentActivity::class.java).setup()
+    val layout = FrameLayout(activityController.get())
+    activityController.get().setContentView(layout)
+    val router = Conductor.attachRouter(activityController.get(), FrameLayout(activityController.get()), null)
+    val controller = TestController()
+    router.setRoot(with(controller))
+    pager = ViewPager2(activityController.get()).also {
+      it.id = ViewCompat.generateViewId()
+    }
+    layout.addView(pager)
+    pager.offscreenPageLimit = 1
+    adapter = object : RouterStateAdapter(controller) {
+      override fun configureRouter(router: Router, position: Int) {
+        if (!router.hasRootController()) {
+          router.setRoot(with(TestController()))
+        }
+      }
+
+      override fun getItemCount(): Int {
+        return 20
+      }
+
+      override fun onViewDetachedFromWindow(holder: RouterViewHolder) {
+        super.onViewDetachedFromWindow(holder)
+
+        destroyedItems.add(holder.currentItemPosition)
+      }
+    }
+    pager.adapter = adapter
+    shadowOf(getMainLooper()).idle()
+  }
+
+  @Test
+  fun testNoMaxSaves() {
+    // Load all pages
+    for (i in 0 until adapter.itemCount) {
+      pager.setCurrentItem(i, false)
+      shadowOf(getMainLooper()).idle()
+    }
+
+    // Ensure all non-visible pages are saved
+    assertEquals(
+      destroyedItems.size,
+      adapter.savedPageHistory.size
+    )
+  }
+
+  @Test
+  fun testMaxSavedSet() {
+    val maxPages = 3
+    adapter.setMaxPagesToStateSave(maxPages)
+
+    // Load all pages
+    for (i in 0 until adapter.itemCount) {
+      pager.setCurrentItem(i, false)
+      shadowOf(getMainLooper()).idle()
+    }
+
+    val firstSelectedItem = adapter.itemCount / 2
+    for (i in adapter.itemCount downTo firstSelectedItem) {
+      pager.setCurrentItem(i, false)
+      shadowOf(getMainLooper()).idle()
+    }
+
+    var savedPages = adapter.savedPageHistory
+
+    // Ensure correct number of pages are saved
+    assertEquals(maxPages, savedPages.size)
+
+    // Ensure correct pages are saved
+    assertEquals(destroyedItems[destroyedItems.lastIndex], savedPages[savedPages.lastIndex].toInt())
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 1], savedPages[savedPages.lastIndex - 1].toInt())
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 2], savedPages[savedPages.lastIndex - 2].toInt())
+
+    val secondSelectedItem = 1
+    for (i in adapter.itemCount downTo secondSelectedItem) {
+      pager.setCurrentItem(i, false)
+      shadowOf(getMainLooper()).idle()
+    }
+
+    savedPages = adapter.savedPageHistory
+
+    // Ensure correct number of pages are saved
+    assertEquals(maxPages, savedPages.size)
+
+    // Ensure correct pages are saved
+    assertEquals(destroyedItems[destroyedItems.lastIndex], savedPages[savedPages.lastIndex].toInt())
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 1], savedPages[savedPages.lastIndex - 1].toInt())
+    assertEquals(destroyedItems[destroyedItems.lastIndex - 2], savedPages[savedPages.lastIndex - 2].toInt())
+  }
+}

conductor-modules/viewpager2/src/test/java/com/bluelinelabs/conductor/viewpager2/util/TestController.java

@@ -1,17 +1,20 @@
-package com.bluelinelabs.conductor.support.util;
+package com.bluelinelabs.conductor.viewpager2.util;
 
-import android.support.annotation.NonNull;
+import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.FrameLayout;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.bluelinelabs.conductor.Controller;
 
 public class TestController extends Controller {
 
-    @NonNull @Override
-    protected View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container) {
+    @Override @NonNull
+    protected View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container, @Nullable Bundle savedViewState) {
         return new FrameLayout(inflater.getContext());
     }
 

conductor/build.gradle

@@ -1,67 +1,47 @@
-buildscript {
-    repositories {
-        jcenter()
-    }
-    dependencies {
-        classpath 'de.mobilej.unmock:UnMockPlugin:0.6.0'
-    }
+plugins {
+    id("com.android.library")
+    id("kotlin-android")
+    id("kotlin-parcelize")
+    alias(libs.plugins.mvnpublish)
 }
 
-apply plugin: 'com.android.library'
-apply plugin: 'de.mobilej.unmock'
-
 android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
-    buildToolsVersion rootProject.ext.buildToolsVersion
+    compileSdk libs.versions.compilesdk.get() as Integer
 
     compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_7
-        targetCompatibility JavaVersion.VERSION_1_7
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+
+    kotlinOptions {
+        jvmTarget = "11"
     }
 
     defaultConfig {
-        minSdkVersion rootProject.ext.minSdkVersion
-        targetSdkVersion rootProject.ext.targetSdkVersion
+        minSdkVersion libs.versions.minsdk.get()
+        targetSdkVersion libs.versions.targetsdk.get()
         versionCode Integer.parseInt(project.VERSION_CODE)
         versionName project.VERSION_NAME
         consumerProguardFiles 'proguard-rules.txt'
     }
-}
 
-configurations {
-    lintChecks
+    namespace "com.bluelinelabs.conductor"
 }
 
 dependencies {
-    testCompile rootProject.ext.junit
-    testCompile rootProject.ext.roboelectric
+    api libs.androidx.activity
+    api libs.androidx.appcompat
+    api libs.androidx.savedstate.ktx
+    testImplementation libs.junit
+    testImplementation libs.robolectric
+    testImplementation libs.kotest
 
-    compile rootProject.ext.supportAnnotations
+    api libs.androidx.lifecycle.runtime
 
-    lintChecks project(path: ':conductor-lint', configuration: 'lintChecks')
+    api libs.androidx.annotation
+    api libs.kotlin.stdlib
 
-    unmock 'org.robolectric:android-all:4.3_r2-robolectric-0'
-}
-
-unMock {
-    keep "android.os.Bundle"
-    keep "android.os.BaseBundle"
-    keep "android.text.TextUtils"
-}
-
-task copyLintJar(type: Copy) {
-    from(configurations.lintChecks) {
-        rename { 'lint.jar' }
-    }
-    into 'build/intermediates/lint/'
-}
-
-project.afterEvaluate {
-    def compileLintTask = project.tasks.find { it.name == 'compileLint' }
-    compileLintTask.dependsOn(copyLintJar)
+    lintPublish project(':conductor-lint')
 }
 
 ext.artifactId = 'conductor'
-
-apply from: rootProject.file('dependencies.gradle')
-apply from: rootProject.file('gradle-mvn-push.gradle')

conductor/proguard-rules.txt

@@ -3,3 +3,6 @@
    public <init>();
    public <init>(android.os.Bundle);
 }
+-keepclassmembers public class * extends com.bluelinelabs.conductor.ControllerChangeHandler {
+   public <init>();
+}

conductor/src/main/AndroidManifest.xml

@@ -1,3 +0,0 @@
-<manifest package="com.bluelinelabs.conductor">
-    <application />
-</manifest>

conductor/src/main/java/com/bluelinelabs/conductor/ActivityHostedRouter.java

@@ -5,10 +5,11 @@ import android.content.Intent;
 import android.content.IntentSender;
 import android.content.IntentSender.SendIntentException;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener;
 import com.bluelinelabs.conductor.internal.LifecycleHandler;
 import com.bluelinelabs.conductor.internal.TransactionIndexer;
@@ -20,6 +21,10 @@ public class ActivityHostedRouter extends Router {
     private LifecycleHandler lifecycleHandler;
     private final TransactionIndexer transactionIndexer = new TransactionIndexer();
 
+    public ActivityHostedRouter() {
+        popRootControllerMode = PopRootControllerMode.NEVER;
+    }
+
     public final void setHost(@NonNull LifecycleHandler lifecycleHandler, @NonNull ViewGroup container) {
         if (this.lifecycleHandler != lifecycleHandler || this.container != container) {
             if (this.container != null && this.container instanceof ControllerChangeListener) {
@@ -57,15 +62,18 @@ public class ActivityHostedRouter extends Router {
     }
 
     @Override
-    public void onActivityDestroyed(@NonNull Activity activity) {
-        super.onActivityDestroyed(activity);
-        lifecycleHandler = null;
+    public void onActivityDestroyed(@NonNull Activity activity, boolean isConfigurationChange) {
+        super.onActivityDestroyed(activity, isConfigurationChange);
+
+        if (!isConfigurationChange) {
+            lifecycleHandler = null;
+        }
     }
 
     @Override
     public final void invalidateOptionsMenu() {
-        if (lifecycleHandler != null && lifecycleHandler.getFragmentManager() != null) {
-            lifecycleHandler.getFragmentManager().invalidateOptionsMenu();
+        if (lifecycleHandler != null && getActivity() != null) {
+            getActivity().invalidateOptionsMenu();
         }
     }
 
@@ -81,7 +89,7 @@ public class ActivityHostedRouter extends Router {
 
     @Override
     void startActivityForResult(@NonNull String instanceId, @NonNull Intent intent, int requestCode) {
-        lifecycleHandler.startActivityForResult(instanceId, intent, requestCode);
+        lifecycleHandler.startActivityForResult(instanceId, intent, requestCode, null);
     }
 
     @Override
@@ -125,7 +133,7 @@ public class ActivityHostedRouter extends Router {
         return this;
     }
 
-    @Override @Nullable
+    @Override @NonNull
     TransactionIndexer getTransactionIndexer() {
         return transactionIndexer;
     }

conductor/src/main/java/com/bluelinelabs/conductor/Backstack.java

@@ -1,130 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-
-import java.util.ArrayDeque;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Deque;
-import java.util.Iterator;
-import java.util.List;
-
-class Backstack implements Iterable<RouterTransaction> {
-
-    private static final String KEY_ENTRIES = "Backstack.entries";
-
-    private final Deque<RouterTransaction> backstack = new ArrayDeque<>();
-
-    @SuppressWarnings("BooleanMethodIsAlwaysInverted")
-    boolean isEmpty() {
-        return backstack.isEmpty();
-    }
-
-    int size() {
-        return backstack.size();
-    }
-
-    @Nullable
-    RouterTransaction root() {
-        return backstack.size() > 0 ? backstack.getLast() : null;
-    }
-
-    @Override @NonNull
-    public Iterator<RouterTransaction> iterator() {
-        return backstack.iterator();
-    }
-
-    @NonNull
-    Iterator<RouterTransaction> reverseIterator() {
-        return backstack.descendingIterator();
-    }
-
-    @NonNull
-    List<RouterTransaction> popTo(@NonNull RouterTransaction transaction) {
-        List<RouterTransaction> popped = new ArrayList<>();
-        if (backstack.contains(transaction)) {
-            while (backstack.peek() != transaction) {
-                RouterTransaction poppedTransaction = pop();
-                popped.add(poppedTransaction);
-            }
-        } else {
-            throw new RuntimeException("Tried to pop to a transaction that was not on the back stack");
-        }
-        return popped;
-    }
-
-    @NonNull
-    RouterTransaction pop() {
-        RouterTransaction popped = backstack.pop();
-        popped.controller.destroy();
-        return popped;
-    }
-
-    @Nullable
-    RouterTransaction peek() {
-        return backstack.peek();
-    }
-
-    void remove(@NonNull RouterTransaction transaction) {
-        backstack.removeFirstOccurrence(transaction);
-    }
-
-    void push(@NonNull RouterTransaction transaction) {
-        backstack.push(transaction);
-    }
-
-    @NonNull
-    List<RouterTransaction> popAll() {
-        List<RouterTransaction> list = new ArrayList<>();
-        while (!isEmpty()) {
-            list.add(pop());
-        }
-        return list;
-    }
-
-    void setBackstack(@NonNull List<RouterTransaction> backstack) {
-        for (RouterTransaction existingTransaction : this.backstack) {
-            boolean contains = false;
-            for (RouterTransaction newTransaction : backstack) {
-                if (existingTransaction.controller == newTransaction.controller) {
-                    contains = true;
-                    break;
-                }
-            }
-
-            if (!contains) {
-                existingTransaction.controller.destroy();
-            }
-        }
-
-        this.backstack.clear();
-        for (RouterTransaction transaction : backstack) {
-            this.backstack.push(transaction);
-        }
-    }
-
-    boolean contains(@NonNull RouterTransaction transaction) {
-        return backstack.contains(transaction);
-    }
-
-    void saveInstanceState(@NonNull Bundle outState) {
-        ArrayList<Bundle> entryBundles = new ArrayList<>(backstack.size());
-        for (RouterTransaction entry : backstack) {
-            entryBundles.add(entry.saveInstanceState());
-        }
-
-        outState.putParcelableArrayList(KEY_ENTRIES, entryBundles);
-    }
-
-    void restoreInstanceState(@NonNull Bundle savedInstanceState) {
-        ArrayList<Bundle> entryBundles = savedInstanceState.getParcelableArrayList(KEY_ENTRIES);
-        if (entryBundles != null) {
-            Collections.reverse(entryBundles);
-            for (Bundle transactionBundle : entryBundles) {
-                backstack.push(new RouterTransaction(transactionBundle));
-            }
-        }
-    }
-}

conductor/src/main/java/com/bluelinelabs/conductor/Backstack.kt

@@ -0,0 +1,102 @@
+package com.bluelinelabs.conductor
+
+import android.os.Bundle
+import java.util.ArrayDeque
+import java.util.Deque
+
+internal class Backstack : Iterable<RouterTransaction> {
+
+  private val backstack: Deque<RouterTransaction> = ArrayDeque()
+
+  val isEmpty: Boolean get() = backstack.isEmpty()
+
+  val size: Int get() = backstack.size
+
+  var onBackstackUpdatedListener: OnBackstackUpdatedListener? = null
+
+  fun root(): RouterTransaction? = backstack.lastOrNull()
+
+  override fun iterator(): Iterator<RouterTransaction> = backstack.toTypedArray().iterator()
+
+  fun reverseIterator(): Iterator<RouterTransaction> = backstack.reversed().iterator()
+
+  fun remove(transaction: RouterTransaction) = backstack.remove(transaction)
+
+  fun popTo(transaction: RouterTransaction): List<RouterTransaction> {
+    if (transaction in backstack) {
+      val popped: MutableList<RouterTransaction> = ArrayList()
+      while (backstack.peek() != transaction) {
+        val poppedTransaction = pop()
+        popped.add(poppedTransaction)
+      }
+      return popped
+    } else {
+      throw RuntimeException("Tried to pop to a transaction that was not on the back stack")
+    }
+  }
+
+  fun pop(): RouterTransaction {
+    return backstack.pop().also {
+      onBackstackUpdatedListener?.onBackstackUpdated()
+      it.controller.destroy()
+    }
+  }
+
+  fun peek(): RouterTransaction? = backstack.peek()
+
+  fun push(transaction: RouterTransaction) {
+    backstack.push(transaction)
+    onBackstackUpdatedListener?.onBackstackUpdated()
+  }
+
+  fun popAll(): List<RouterTransaction> {
+    val list: MutableList<RouterTransaction> = ArrayList()
+    while (!isEmpty) {
+      list.add(pop())
+    }
+    return list
+  }
+
+  fun setBackstack(backstack: List<RouterTransaction>) {
+    this.backstack.clear()
+    backstack.forEach { transaction ->
+      this.backstack.push(transaction)
+    }
+
+    onBackstackUpdatedListener?.onBackstackUpdated()
+  }
+
+  operator fun contains(controller: Controller): Boolean {
+    return backstack.any {
+      it.controller == controller
+    }
+  }
+
+  fun saveInstanceState(outState: Bundle) {
+    val entryBundles = ArrayList<Bundle>(backstack.size)
+    backstack.mapTo(entryBundles) {
+      it.saveInstanceState()
+    }
+    outState.putParcelableArrayList(KEY_ENTRIES, entryBundles)
+  }
+
+  fun restoreInstanceState(savedInstanceState: Bundle) {
+    val entryBundles = savedInstanceState.getParcelableArrayList<Bundle?>(KEY_ENTRIES)
+    if (entryBundles != null) {
+      entryBundles.reverse()
+      for (transactionBundle in entryBundles) {
+        backstack.push(RouterTransaction(transactionBundle!!))
+      }
+    }
+
+    onBackstackUpdatedListener?.onBackstackUpdated()
+  }
+
+  fun interface OnBackstackUpdatedListener {
+    fun onBackstackUpdated()
+  }
+
+  companion object {
+    private const val KEY_ENTRIES = "Backstack.entries"
+  }
+}

conductor/src/main/java/com/bluelinelabs/conductor/ChangeHandlerFrameLayout.java

@@ -1,56 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.annotation.TargetApi;
-import android.content.Context;
-import android.os.Build;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.util.AttributeSet;
-import android.view.MotionEvent;
-import android.view.ViewGroup;
-import android.widget.FrameLayout;
-
-import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener;
-
-/**
- * A FrameLayout implementation that can be used to block user interactions while
- * {@link ControllerChangeHandler}s are performing changes. It is not required to use this
- * ViewGroup, but it can be helpful.
- */
-public class ChangeHandlerFrameLayout extends FrameLayout implements ControllerChangeListener {
-
-    private int inProgressTransactionCount;
-
-    public ChangeHandlerFrameLayout(Context context) {
-        super(context);
-    }
-
-    public ChangeHandlerFrameLayout(Context context, AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    public ChangeHandlerFrameLayout(Context context, AttributeSet attrs, int defStyleAttr) {
-        super(context, attrs, defStyleAttr);
-    }
-
-    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
-    public ChangeHandlerFrameLayout(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
-        super(context, attrs, defStyleAttr, defStyleRes);
-    }
-
-    @Override
-    public boolean onInterceptTouchEvent(MotionEvent ev) {
-        return (inProgressTransactionCount > 0) || super.onInterceptTouchEvent(ev);
-    }
-
-    @Override
-    public void onChangeStarted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler) {
-        inProgressTransactionCount++;
-    }
-
-    @Override
-    public void onChangeCompleted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler) {
-        inProgressTransactionCount--;
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/ChangeHandlerFrameLayout.kt

@@ -0,0 +1,60 @@
+package com.bluelinelabs.conductor
+
+import android.annotation.TargetApi
+import android.content.Context
+import android.os.Build
+import android.util.AttributeSet
+import android.view.MotionEvent
+import android.view.ViewGroup
+import android.widget.FrameLayout
+import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener
+
+/**
+ * A FrameLayout implementation that can be used to block user interactions while
+ * [ControllerChangeHandler]s are performing changes. It is not required to use this
+ * ViewGroup, but it can be helpful.
+ */
+open class ChangeHandlerFrameLayout : FrameLayout, ControllerChangeListener {
+
+  private var inProgressTransactionCount = 0
+
+  constructor(context: Context) : super(context)
+  constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)
+  constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(
+    context,
+    attrs,
+    defStyleAttr
+  )
+
+  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
+  constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int, defStyleRes: Int) : super(
+    context,
+    attrs,
+    defStyleAttr,
+    defStyleRes
+  )
+
+  override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
+    return inProgressTransactionCount > 0 || super.onInterceptTouchEvent(ev)
+  }
+
+  override fun onChangeStarted(
+    to: Controller?,
+    from: Controller?,
+    isPush: Boolean,
+    container: ViewGroup,
+    handler: ControllerChangeHandler
+  ) {
+    inProgressTransactionCount++
+  }
+
+  override fun onChangeCompleted(
+    to: Controller?,
+    from: Controller?,
+    isPush: Boolean,
+    container: ViewGroup,
+    handler: ControllerChangeHandler
+  ) {
+    inProgressTransactionCount--
+  }
+}

conductor/src/main/java/com/bluelinelabs/conductor/Conductor.java

@@ -1,44 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.app.Activity;
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.annotation.UiThread;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.internal.LifecycleHandler;
-import com.bluelinelabs.conductor.internal.ThreadUtils;
-
-/**
- * Point of initial interaction with Conductor. Used to attach a {@link Router} to your Activity.
- */
-public final class Conductor {
-
-    private Conductor() {}
-
-    /**
-     * Conductor will create a {@link Router} that has been initialized for your Activity and containing ViewGroup.
-     * If an existing {@link Router} is already associated with this Activity/ViewGroup pair, either in memory
-     * or in the savedInstanceState, that router will be used and rebound instead of creating a new one with
-     * an empty backstack.
-     *
-     * @param activity The Activity that will host the {@link Router} being attached.
-     * @param container The ViewGroup in which the {@link Router}'s {@link Controller} views will be hosted
-     * @param savedInstanceState The savedInstanceState passed into the hosting Activity's onCreate method. Used
-     *                           for restoring the Router's state if possible.
-     * @return A fully configured {@link Router} instance for use with this Activity/ViewGroup pair.
-     */
-    @NonNull @UiThread
-    public static Router attachRouter(@NonNull Activity activity, @NonNull ViewGroup container, @Nullable Bundle savedInstanceState) {
-        ThreadUtils.ensureMainThread();
-
-        LifecycleHandler lifecycleHandler = LifecycleHandler.install(activity);
-
-        Router router = lifecycleHandler.getRouter(container, savedInstanceState);
-        router.rebindIfNeeded();
-
-        return router;
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/Conductor.kt

@@ -0,0 +1,41 @@
+package com.bluelinelabs.conductor
+
+import android.app.Activity
+import android.os.Bundle
+import android.view.ViewGroup
+import androidx.annotation.UiThread
+import com.bluelinelabs.conductor.internal.LifecycleHandler
+import com.bluelinelabs.conductor.internal.ensureMainThread
+
+object Conductor {
+
+  /**
+   * Conductor will create a [Router] that has been initialized for your Activity and containing ViewGroup.
+   * If an existing [Router] is already associated with this Activity/ViewGroup pair, either in memory
+   * or in the savedInstanceState, that router will be used and rebound instead of creating a new one with
+   * an empty backstack.
+   *
+   * @param activity The Activity that will host the [Router] being attached.
+   * @param container The ViewGroup in which the [Router]'s [Controller] views will be hosted
+   * @param savedInstanceState The savedInstanceState passed into the hosting Activity's onCreate method. Used
+   * for restoring the Router's state if possible.
+   * @param allowExperimentalAndroidXBacking Use AndroidX backing if true and if the activity parameter is a
+   * FragmentActivity.
+   * @return A fully configured [Router] instance for use with this Activity/ViewGroup pair.
+   */
+  @UiThread
+  @JvmStatic
+  @JvmOverloads
+  fun attachRouter(
+    activity: Activity,
+    container: ViewGroup,
+    savedInstanceState: Bundle?,
+    allowExperimentalAndroidXBacking: Boolean = true,
+  ): Router {
+    ensureMainThread()
+    return LifecycleHandler.install(activity, allowAndroidXBacking = allowExperimentalAndroidXBacking)
+      .getRouter(container, savedInstanceState)
+      .also { it.rebindIfNeeded() }
+      .setPopRootControllerMode(Router.PopRootControllerMode.NEVER)
+  }
+}

conductor/src/main/java/com/bluelinelabs/conductor/ControllerChangeHandler.java

@@ -1,309 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-import android.view.ViewParent;
-
-import com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler;
-import com.bluelinelabs.conductor.internal.ClassUtils;
-
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
-/**
- * ControllerChangeHandlers are responsible for swapping the View for one Controller to the View
- * of another. They can be useful for performing animations and transitions between Controllers. Several
- * default ControllerChangeHandlers are included.
- */
-public abstract class ControllerChangeHandler {
-
-    private static final String KEY_CLASS_NAME = "ControllerChangeHandler.className";
-    private static final String KEY_SAVED_STATE = "ControllerChangeHandler.savedState";
-
-    private static final Map<String, ChangeHandlerData> inProgressChangeHandlers = new HashMap<>();
-
-    private boolean forceRemoveViewOnPush;
-    private boolean hasBeenUsed;
-
-    /**
-     * Responsible for swapping Views from one Controller to another.
-     *
-     * @param container      The container these Views are hosted in.
-     * @param from           The previous View in the container or {@code null} if there was no Controller before this transition
-     * @param to             The next View that should be put in the container or {@code null} if no Controller is being transitioned to
-     * @param isPush         True if this is a push transaction, false if it's a pop.
-     * @param changeListener This listener must be called when any transitions or animations are completed.
-     */
-    public abstract void performChange(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, @NonNull ControllerChangeCompletedListener changeListener);
-
-    public ControllerChangeHandler() {
-        ensureDefaultConstructor();
-    }
-
-    /**
-     * Saves any data about this handler to a Bundle in case the application is killed.
-     *
-     * @param bundle The Bundle into which data should be stored.
-     */
-    public void saveToBundle(@NonNull Bundle bundle) { }
-
-    /**
-     * Restores data that was saved in the {@link #saveToBundle(Bundle bundle)} method.
-     *
-     * @param bundle The bundle that has data to be restored
-     */
-    public void restoreFromBundle(@NonNull Bundle bundle) { }
-
-    /**
-     * Will be called on change handlers that push a controller if the controller being pushed is
-     * popped before it has completed.
-     *
-     * @param newHandler The change handler that has caused this push to be aborted
-     * @param newTop     The Controller that will now be at the top of the backstack or {@code null}
-     *                   if there will be no new Controller at the top
-     */
-    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) { }
-
-    /**
-     * Will be called on change handlers that push a controller if the controller being pushed is
-     * needs to be attached immediately, without any animations or transitions.
-     */
-    public void completeImmediately() { }
-
-    /**
-     * Returns a copy of this ControllerChangeHandler. This method is internally used by the library, so
-     * ensure it will return an exact copy of your handler if overriding. If not overriding, the handler
-     * will be saved and restored from the Bundle format.
-     */
-    @NonNull
-    public ControllerChangeHandler copy() {
-        return fromBundle(toBundle());
-    }
-
-    /**
-     * Returns whether or not this is a reusable ControllerChangeHandler. Defaults to false and should
-     * ONLY be overridden if there are absolutely no side effects to using this handler more than once.
-     * In the case that a handler is not reusable, it will be copied using the {@link #copy()} method
-     * prior to use.
-     */
-    public boolean isReusable() {
-        return false;
-    }
-
-    @NonNull
-    final Bundle toBundle() {
-        Bundle bundle = new Bundle();
-        bundle.putString(KEY_CLASS_NAME, getClass().getName());
-
-        Bundle savedState = new Bundle();
-        saveToBundle(savedState);
-        bundle.putBundle(KEY_SAVED_STATE, savedState);
-
-        return bundle;
-    }
-
-    private void ensureDefaultConstructor() {
-        try {
-            getClass().getConstructor();
-        } catch (Exception e) {
-            throw new RuntimeException(getClass() + " does not have a default constructor.");
-        }
-    }
-
-    @Nullable
-    public static ControllerChangeHandler fromBundle(@Nullable Bundle bundle) {
-        if (bundle != null) {
-            String className = bundle.getString(KEY_CLASS_NAME);
-            ControllerChangeHandler changeHandler = ClassUtils.newInstance(className);
-            //noinspection ConstantConditions
-            changeHandler.restoreFromBundle(bundle.getBundle(KEY_SAVED_STATE));
-            return changeHandler;
-        } else {
-            return null;
-        }
-    }
-
-    static boolean completeHandlerImmediately(@NonNull String controllerInstanceId) {
-        ChangeHandlerData changeHandlerData = inProgressChangeHandlers.get(controllerInstanceId);
-        if (changeHandlerData != null) {
-            changeHandlerData.changeHandler.completeImmediately();
-            inProgressChangeHandlers.remove(controllerInstanceId);
-            return true;
-        }
-        return false;
-    }
-
-    static void abortOrComplete(@NonNull Controller toAbort, @Nullable Controller newController, @NonNull ControllerChangeHandler newChangeHandler) {
-        ChangeHandlerData changeHandlerData = inProgressChangeHandlers.get(toAbort.getInstanceId());
-        if (changeHandlerData != null) {
-            if (changeHandlerData.isPush) {
-                changeHandlerData.changeHandler.onAbortPush(newChangeHandler, newController);
-            } else {
-                changeHandlerData.changeHandler.completeImmediately();
-            }
-
-            inProgressChangeHandlers.remove(toAbort.getInstanceId());
-        }
-    }
-
-    static void executeChange(@NonNull final ChangeTransaction transaction) {
-        executeChange(transaction.to, transaction.from, transaction.isPush, transaction.container, transaction.changeHandler, transaction.listeners);
-    }
-
-    private static void executeChange(@Nullable final Controller to, @Nullable final Controller from, final boolean isPush, @Nullable final ViewGroup container, @Nullable final ControllerChangeHandler inHandler, @NonNull final List<ControllerChangeListener> listeners) {
-        if (container != null) {
-            final ControllerChangeHandler handler;
-            if (inHandler == null) {
-                handler = new SimpleSwapChangeHandler();
-            } else if (inHandler.hasBeenUsed && !inHandler.isReusable()) {
-                handler = inHandler.copy();
-            } else {
-                handler = inHandler;
-            }
-            handler.hasBeenUsed = true;
-
-            if (from != null) {
-                if (isPush) {
-                    completeHandlerImmediately(from.getInstanceId());
-                } else {
-                    abortOrComplete(from, to, handler);
-                }
-            }
-
-            if (to != null) {
-                inProgressChangeHandlers.put(to.getInstanceId(), new ChangeHandlerData(handler, isPush));
-            }
-
-            for (ControllerChangeListener listener : listeners) {
-                listener.onChangeStarted(to, from, isPush, container, handler);
-            }
-
-            final ControllerChangeType toChangeType = isPush ? ControllerChangeType.PUSH_ENTER : ControllerChangeType.POP_ENTER;
-            final ControllerChangeType fromChangeType = isPush ? ControllerChangeType.PUSH_EXIT : ControllerChangeType.POP_EXIT;
-
-            final View toView;
-            if (to != null) {
-                toView = to.inflate(container);
-                to.changeStarted(handler, toChangeType);
-            } else {
-                toView = null;
-            }
-
-            final View fromView;
-            if (from != null) {
-                fromView = from.getView();
-                from.changeStarted(handler, fromChangeType);
-            } else {
-                fromView = null;
-            }
-
-            handler.performChange(container, fromView, toView, isPush, new ControllerChangeCompletedListener() {
-                @Override
-                public void onChangeCompleted() {
-                    if (from != null) {
-                        from.changeEnded(handler, fromChangeType);
-                    }
-
-                    if (to != null) {
-                        inProgressChangeHandlers.remove(to.getInstanceId());
-                        to.changeEnded(handler, toChangeType);
-                    }
-
-                    for (ControllerChangeListener listener : listeners) {
-                        listener.onChangeCompleted(to, from, isPush, container, handler);
-                    }
-
-                    if (handler.forceRemoveViewOnPush && fromView != null) {
-                        ViewParent fromParent = fromView.getParent();
-                        if (fromParent != null && fromParent instanceof ViewGroup) {
-                            ((ViewGroup)fromParent).removeView(fromView);
-                        }
-                    }
-
-                    if (handler.removesFromViewOnPush() && from != null) {
-                        from.setNeedsAttach(false);
-                    }
-                }
-            });
-        }
-    }
-
-    public boolean removesFromViewOnPush() {
-        return true;
-    }
-
-    public void setForceRemoveViewOnPush(boolean force) {
-        forceRemoveViewOnPush = force;
-    }
-
-    static class ChangeTransaction {
-        @Nullable final Controller to;
-        @Nullable final Controller from;
-        final boolean isPush;
-        @Nullable final ViewGroup container;
-        @Nullable final ControllerChangeHandler changeHandler;
-        @NonNull final List<ControllerChangeListener> listeners;
-
-        public ChangeTransaction(@Nullable Controller to, @Nullable Controller from, boolean isPush, @Nullable ViewGroup container, @Nullable ControllerChangeHandler changeHandler, @NonNull List<ControllerChangeListener> listeners) {
-            this.to = to;
-            this.from = from;
-            this.isPush = isPush;
-            this.container = container;
-            this.changeHandler = changeHandler;
-            this.listeners = listeners;
-        }
-    }
-
-    /**
-     * A listener interface useful for allowing external classes to be notified of change events.
-     */
-    public interface ControllerChangeListener {
-        /**
-         * Called when a {@link ControllerChangeHandler} has started changing {@link Controller}s
-         *
-         * @param to        The new Controller or {@code null} if no Controller is being transitioned to
-         * @param from      The old Controller or {@code null} if there was no Controller before this transition
-         * @param isPush    True if this is a push operation, or false if it's a pop.
-         * @param container The containing ViewGroup
-         * @param handler   The change handler being used.
-         */
-        void onChangeStarted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler);
-
-        /**
-         * Called when a {@link ControllerChangeHandler} has completed changing {@link Controller}s
-         *
-         * @param to        The new Controller or {@code null} if no Controller is being transitioned to
-         * @param from      The old Controller or {@code null} if there was no Controller before this transition
-         * @param isPush    True if this was a push operation, or false if it's a pop
-         * @param container The containing ViewGroup
-         * @param handler   The change handler that was used.
-         */
-        void onChangeCompleted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler);
-    }
-
-    /**
-     * A simplified listener for being notified when the change is complete. This MUST be called by any custom
-     * ControllerChangeHandlers in order to ensure that {@link Controller}s will be notified of this change.
-     */
-    public interface ControllerChangeCompletedListener {
-        /**
-         * Called when the change is complete.
-         */
-        void onChangeCompleted();
-    }
-
-    private static class ChangeHandlerData {
-        public final ControllerChangeHandler changeHandler;
-        public final boolean isPush;
-
-        public ChangeHandlerData(ControllerChangeHandler changeHandler, boolean isPush) {
-            this.changeHandler = changeHandler;
-            this.isPush = isPush;
-        }
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/ControllerChangeHandler.kt

@@ -0,0 +1,332 @@
+package com.bluelinelabs.conductor
+
+import android.os.Bundle
+import android.view.View
+import android.view.ViewGroup
+import androidx.activity.BackEventCompat
+import androidx.annotation.RestrictTo
+import com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler
+import com.bluelinelabs.conductor.internal.ClassUtils
+
+/**
+ * ControllerChangeHandlers are responsible for swapping the View for one Controller to the View
+ * of another. They can be useful for performing animations and transitions between Controllers. Several
+ * default ControllerChangeHandlers are included.
+ */
+abstract class ControllerChangeHandler {
+  private var forceRemoveViewOnPush = false
+
+  /**
+   * Returns whether or not this is a reusable ControllerChangeHandler. Defaults to false and should
+   * ONLY be overridden if there are absolutely no side effects to using this handler more than once.
+   * In the case that a handler is not reusable, it will be copied using the [.copy] method
+   * prior to use.
+   */
+  open val isReusable: Boolean = false
+
+  /**
+   * Returns whether or not this handler removes the `from` view from the container when performing a push.
+   *
+   * If this is true:
+   * - This handler's implementation of [performChange] should remove `from` from `container`
+   *   before calling `changeListener.onChangeCompleted()`
+   * - When a controller is pushed, the previous controller will be detached and its view will be destroyed
+   *
+   * If this is false:
+   * - This handler's implementation of [performChange] should only remove `from` from `container`
+   *   when `isPush` is false
+   * - When a controller is pushed, the previous controller will stay attached and its view will remain created
+   * - When a view is recreated (e.g. after a configuration change), any controllers underneath a transaction
+   *   using this handler will have their view recreated and attached, even though they're not the top-most
+   *   controller
+   *
+   * If a controller pushed onto the backstack will completely cover the previous controller,
+   * using a change handler with [removesFromViewOnPush] true should result in no visual interruption
+   * to the user, while allowing the previous controller's view to be destroyed to reclaim resources.
+   * If instead, the previous controller should still be visible after the new controller is pushed,
+   * using a change handler with [removesFromViewOnPush] false will keep the previous controller's
+   * view in the view hierarchy, where it can still be seen (and even interacted with).
+   */
+  open val removesFromViewOnPush: Boolean = true
+
+  private var hasBeenUsed = false
+
+  open val enableOnBackGestureCallbacks = false
+
+  init {
+    try {
+      javaClass.getConstructor()
+    } catch (e: Throwable) {
+      throw RuntimeException("$javaClass does not have a default constructor.")
+    }
+  }
+
+  /**
+   * Responsible for swapping Views from one Controller to another.
+   *
+   * @param container      The container these Views are hosted in.
+   * @param from           The previous View in the container or `null` if there was no Controller before this transition
+   * @param to             The next View that should be put in the container or `null` if no Controller is being transitioned to
+   * @param isPush         True if this is a push transaction, false if it's a pop.
+   * @param changeListener This listener must be called when any transitions or animations are completed.
+   */
+  abstract fun performChange(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    changeListener: ControllerChangeCompletedListener,
+  )
+
+  /**
+   * Saves any data about this handler to a Bundle in case the application is killed.
+   *
+   * @param bundle The Bundle into which data should be stored.
+   */
+  open fun saveToBundle(bundle: Bundle) {}
+
+  /**
+   * Restores data that was saved in the [.saveToBundle] method.
+   *
+   * @param bundle The bundle that has data to be restored
+   */
+  open fun restoreFromBundle(bundle: Bundle) {}
+
+  /**
+   * Will be called on change handlers that push a controller if the controller being pushed is
+   * popped before it has completed.
+   *
+   * @param newHandler The change handler that has caused this push to be aborted
+   * @param newTop     The Controller that will now be at the top of the backstack or `null`
+   * if there will be no new Controller at the top
+   */
+  open fun onAbortPush(newHandler: ControllerChangeHandler, newTop: Controller?) {}
+
+  /**
+   * Will be called on change handlers that push a controller if the controller being pushed is
+   * needs to be attached immediately, without any animations or transitions.
+   */
+  open fun completeImmediately() {}
+
+  /**
+   * Returns a copy of this ControllerChangeHandler. This method is internally used by the library, so
+   * ensure it will return an exact copy of your handler if overriding. If not overriding, the handler
+   * will be saved and restored from the Bundle format.
+   */
+  open fun copy(): ControllerChangeHandler = fromBundle(toBundle())!!
+
+  open fun handleOnBackStarted(container: ViewGroup, to: View?, from: View, event: BackEventCompat) {}
+
+  open fun handleOnBackProgressed(container: ViewGroup, to: View?, from: View, event: BackEventCompat) {}
+
+  open fun handleOnBackCancelled(container: ViewGroup, to: View?, from: View) {}
+
+  protected open fun onEnd() {}
+
+  fun toBundle(): Bundle {
+    val bundle = Bundle()
+    bundle.putString(KEY_CLASS_NAME, javaClass.name)
+
+    val savedState = Bundle()
+    saveToBundle(savedState)
+    bundle.putBundle(KEY_SAVED_STATE, savedState)
+
+    return bundle
+  }
+
+  // Internal modifier plays weirdly with Java, which is what Router is still written in.
+  @RestrictTo(RestrictTo.Scope.LIBRARY)
+  fun setForceRemoveViewOnPush(forceRemoveViewOnPush: Boolean) {
+    this.forceRemoveViewOnPush = forceRemoveViewOnPush
+  }
+
+  /**
+   * A listener interface useful for allowing external classes to be notified of change events.
+   */
+  interface ControllerChangeListener {
+    /**
+     * Called when a [ControllerChangeHandler] has started changing [Controller]s
+     *
+     * @param to        The new Controller or `null` if no Controller is being transitioned to
+     * @param from      The old Controller or `null` if there was no Controller before this transition
+     * @param isPush    True if this is a push operation, or false if it's a pop.
+     * @param container The containing ViewGroup
+     * @param handler   The change handler being used.
+     */
+    fun onChangeStarted(
+      to: Controller?,
+      from: Controller?,
+      isPush: Boolean,
+      container: ViewGroup,
+      handler: ControllerChangeHandler,
+    )
+
+    /**
+     * Called when a [ControllerChangeHandler] has completed changing [Controller]s
+     *
+     * @param to        The new Controller or `null` if no Controller is being transitioned to
+     * @param from      The old Controller or `null` if there was no Controller before this transition
+     * @param isPush    True if this was a push operation, or false if it's a pop
+     * @param container The containing ViewGroup
+     * @param handler   The change handler that was used.
+     */
+    fun onChangeCompleted(
+      to: Controller?,
+      from: Controller?,
+      isPush: Boolean,
+      container: ViewGroup,
+      handler: ControllerChangeHandler,
+    )
+  }
+
+  class ChangeTransaction(
+    @JvmField val to: Controller?,
+    @JvmField val from: Controller?,
+    @JvmField val isPush: Boolean,
+    @JvmField val container: ViewGroup?,
+    @JvmField val changeHandler: ControllerChangeHandler?,
+    @JvmField val listeners: List<ControllerChangeListener>,
+  )
+
+  /**
+   * A simplified listener for being notified when the change is complete. This MUST be called by any custom
+   * ControllerChangeHandlers in order to ensure that [Controller]s will be notified of this change.
+   */
+  interface ControllerChangeCompletedListener {
+    /**
+     * Called when the change is complete.
+     */
+    fun onChangeCompleted()
+  }
+
+  class ChangeHandlerData(val changeHandler: ControllerChangeHandler, val isPush: Boolean)
+
+  companion object {
+    private const val KEY_CLASS_NAME = "ControllerChangeHandler.className"
+    private const val KEY_SAVED_STATE = "ControllerChangeHandler.savedState"
+    val inProgressChangeHandlers: MutableMap<String, ChangeHandlerData> = HashMap()
+
+    @JvmStatic
+    fun fromBundle(bundle: Bundle?): ControllerChangeHandler? {
+      val bundle = bundle ?: return null
+      val className = bundle.getString(KEY_CLASS_NAME) ?: return null
+      val savedState = bundle.getBundle(KEY_SAVED_STATE) ?: return null
+
+      return ClassUtils.newInstance<ControllerChangeHandler>(className)?.also {
+        it.restoreFromBundle(savedState)
+      }
+    }
+
+    @JvmStatic
+    fun completeHandlerImmediately(controllerInstanceId: String): Boolean {
+      inProgressChangeHandlers[controllerInstanceId]?.let { changeHandlerData ->
+        changeHandlerData.changeHandler.completeImmediately()
+        inProgressChangeHandlers.remove(controllerInstanceId)
+        return true
+      }
+
+      return false
+    }
+
+    fun abortOrComplete(toAbort: Controller, newController: Controller?, newChangeHandler: ControllerChangeHandler) {
+      inProgressChangeHandlers[toAbort.getInstanceId()]?.let { changeHandlerData ->
+        if (changeHandlerData.isPush) {
+          changeHandlerData.changeHandler.onAbortPush(newChangeHandler, newController)
+        } else {
+          changeHandlerData.changeHandler.completeImmediately()
+        }
+        inProgressChangeHandlers.remove(toAbort.getInstanceId())
+      }
+    }
+
+    @JvmStatic
+    fun executeChange(transaction: ChangeTransaction) {
+      executeChange(
+        to = transaction.to,
+        from = transaction.from,
+        isPush = transaction.isPush,
+        container = transaction.container,
+        inHandler = transaction.changeHandler,
+        listeners = transaction.listeners,
+      )
+    }
+
+    private fun executeChange(
+      to: Controller?,
+      from: Controller?,
+      isPush: Boolean,
+      container: ViewGroup?,
+      inHandler: ControllerChangeHandler?,
+      listeners: List<ControllerChangeListener>,
+    ) {
+      container ?: return
+
+      val handler: ControllerChangeHandler = if (inHandler == null) {
+        SimpleSwapChangeHandler()
+      } else if (inHandler.hasBeenUsed && !inHandler.isReusable) {
+        inHandler.copy()
+      } else {
+        inHandler
+      }
+
+      handler.hasBeenUsed = true
+
+      if (from != null) {
+        if (isPush) {
+          completeHandlerImmediately(from.getInstanceId())
+        } else {
+          abortOrComplete(from, to, handler)
+        }
+      }
+
+      if (to != null) {
+        inProgressChangeHandlers[to.getInstanceId()] = ChangeHandlerData(handler, isPush)
+      }
+
+      listeners.forEach { it.onChangeStarted(to, from, isPush, container, handler) }
+
+      val toChangeType = if (isPush) ControllerChangeType.PUSH_ENTER else ControllerChangeType.POP_ENTER
+      val fromChangeType = if (isPush) ControllerChangeType.PUSH_EXIT else ControllerChangeType.POP_EXIT
+      val toView = to?.let {
+        it.inflate(container).also {
+          to.changeStarted(handler, toChangeType)
+        }
+      }
+
+      val fromView = from?.let {
+        from.getView().also {
+          from.changeStarted(handler, fromChangeType)
+        }
+      }
+
+      handler.performChange(
+        container = container,
+        from = fromView,
+        to = toView,
+        isPush = isPush,
+        changeListener = object : ControllerChangeCompletedListener {
+          override fun onChangeCompleted() {
+            from?.changeEnded(handler, fromChangeType)
+
+            to?.let {
+              inProgressChangeHandlers.remove(it.getInstanceId())
+              it.changeEnded(handler, toChangeType)
+            }
+
+            listeners.forEach { it.onChangeCompleted(to, from, isPush, container, handler) }
+
+            if (handler.forceRemoveViewOnPush) {
+              (fromView?.parent as? ViewGroup)?.let {
+                it.removeView(fromView)
+              }
+            }
+
+            if (handler.removesFromViewOnPush) {
+              from?.needsAttach = false
+            }
+          }
+        },
+      )
+    }
+  }
+}

conductor/src/main/java/com/bluelinelabs/conductor/ControllerChangeType.java

@@ -1,26 +0,0 @@
-package com.bluelinelabs.conductor;
-
-/**
- * All possible types of {@link Controller} changes to be used in {@link ControllerChangeHandler}s
- */
-public enum ControllerChangeType {
-    /** The Controller is being pushed to the host container */
-    PUSH_ENTER(true, true),
-
-    /** The Controller is being pushed to the backstack as another Controller is pushed to the host container */
-    PUSH_EXIT(true, false),
-
-    /** The Controller is being popped from the backstack and placed in the host container as another Controller is popped */
-    POP_ENTER(false, true),
-
-    /** The Controller is being popped from the host container */
-    POP_EXIT(false, false);
-
-    public boolean isPush;
-    public boolean isEnter;
-
-    ControllerChangeType(boolean isPush, boolean isEnter) {
-        this.isPush = isPush;
-        this.isEnter = isEnter;
-    }
-}

conductor/src/main/java/com/bluelinelabs/conductor/ControllerChangeType.kt

@@ -0,0 +1,18 @@
+package com.bluelinelabs.conductor
+
+/**
+ * All possible types of [Controller] changes to be used in [ControllerChangeHandler]s
+ */
+enum class ControllerChangeType(@JvmField val isPush: Boolean, @JvmField val isEnter: Boolean) {
+  /** The Controller is being pushed to the host container  */
+  PUSH_ENTER(true, true),
+
+  /** The Controller is being pushed to the backstack as another Controller is pushed to the host container  */
+  PUSH_EXIT(true, false),
+
+  /** The Controller is being popped from the backstack and placed in the host container as another Controller is popped  */
+  POP_ENTER(false, true),
+
+  /** The Controller is being popped from the host container  */
+  POP_EXIT(false, false);
+}

conductor/src/main/java/com/bluelinelabs/conductor/ControllerHostedRouter.java

@@ -5,48 +5,68 @@ import android.content.Intent;
 import android.content.IntentSender;
 import android.content.IntentSender.SendIntentException;
 import android.os.Bundle;
-import android.support.annotation.IdRes;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
+import android.text.TextUtils;
 import android.view.ViewGroup;
 
+import androidx.annotation.IdRes;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener;
 import com.bluelinelabs.conductor.internal.TransactionIndexer;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 
 class ControllerHostedRouter extends Router {
 
     private final String KEY_HOST_ID = "ControllerHostedRouter.hostId";
     private final String KEY_TAG = "ControllerHostedRouter.tag";
+    private final String KEY_BOUND_TO_CONTAINER = "ControllerHostedRouter.boundToContainer";
 
     private Controller hostController;
 
     @IdRes private int hostId;
     private String tag;
     private boolean isDetachFrozen;
+    private boolean boundToContainer;
 
-    ControllerHostedRouter() { }
-
-    ControllerHostedRouter(int hostId, @Nullable String tag) {
-        this.hostId = hostId;
-        this.tag = tag;
+    ControllerHostedRouter() {
+        popRootControllerMode = PopRootControllerMode.POP_ROOT_CONTROLLER_BUT_NOT_VIEW;
     }
 
-    final void setHost(@NonNull Controller controller, @NonNull ViewGroup container) {
+    ControllerHostedRouter(int hostId, @Nullable String tag, boolean boundToContainer) {
+        this();
+        if (!boundToContainer && tag == null) {
+            throw new IllegalStateException("ControllerHostedRouter can't be created without a tag if not bounded to its container");
+        }
+        this.hostId = hostId;
+        this.tag = tag;
+        this.boundToContainer = boundToContainer;
+    }
+
+    final void setHostController(@NonNull Controller controller) {
+        if (hostController == null) {
+            hostController = controller;
+            setOnBackPressedDispatcherEnabled(controller.onBackPressedDispatcherEnabled);
+        }
+    }
+
+    final void setHostContainer(@NonNull Controller controller, @NonNull ViewGroup container) {
         if (hostController != controller || this.container != container) {
             removeHost();
 
             if (container instanceof ControllerChangeListener) {
-                addChangeListener((ControllerChangeListener)container);
+                addChangeListener((ControllerChangeListener) container);
             }
 
             hostController = controller;
             this.container = container;
+            setOnBackPressedDispatcherEnabled(controller.onBackPressedDispatcherEnabled);
 
             for (RouterTransaction transaction : backstack) {
-                transaction.controller.setParentController(controller);
+                transaction.controller().setParentController(controller);
             }
 
             watchContainerAttach();
@@ -55,7 +75,7 @@ class ControllerHostedRouter extends Router {
 
     final void removeHost() {
         if (container != null && container instanceof ControllerChangeListener) {
-            removeChangeListener((ControllerChangeListener)container);
+            removeChangeListener((ControllerChangeListener) container);
         }
 
         final List<Controller> controllersToDestroy = new ArrayList<>(destroyingControllers);
@@ -65,20 +85,19 @@ class ControllerHostedRouter extends Router {
             }
         }
         for (RouterTransaction transaction : backstack) {
-            if (transaction.controller.getView() != null) {
-                transaction.controller.detach(transaction.controller.getView(), true, false);
+            if (transaction.controller().getView() != null) {
+                transaction.controller().detach(transaction.controller().getView(), true, false);
             }
         }
 
         prepareForContainerRemoval();
-        hostController = null;
         container = null;
     }
 
     final void setDetachFrozen(boolean frozen) {
         isDetachFrozen = frozen;
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.setDetachFrozen(frozen);
+            transaction.controller().setDetachFrozen(frozen);
         }
     }
 
@@ -91,7 +110,7 @@ class ControllerHostedRouter extends Router {
     @Override
     protected void pushToBackstack(@NonNull RouterTransaction entry) {
         if (isDetachFrozen) {
-            entry.controller.setDetachFrozen(true);
+            entry.controller().setDetachFrozen(true);
         }
         super.pushToBackstack(entry);
     }
@@ -100,20 +119,35 @@ class ControllerHostedRouter extends Router {
     public void setBackstack(@NonNull List<RouterTransaction> newBackstack, @Nullable ControllerChangeHandler changeHandler) {
         if (isDetachFrozen) {
             for (RouterTransaction transaction : newBackstack) {
-                transaction.controller.setDetachFrozen(true);
+                transaction.controller().setDetachFrozen(true);
             }
         }
         super.setBackstack(newBackstack, changeHandler);
     }
 
+    @Override
+    void performControllerChange(@Nullable RouterTransaction to, @Nullable RouterTransaction from, boolean isPush) {
+        super.performControllerChange(to, from, isPush);
+
+        // If we're pushing a transaction that will detach controllers to an unattached child
+        // router, we need mark all other controllers as NOT needing to be reattached.
+        if (to != null && !hostController.isAttached()) {
+            if (to.pushChangeHandler() == null || to.pushChangeHandler().getRemovesFromViewOnPush()) {
+                for (RouterTransaction transaction : backstack) {
+                    transaction.controller().setNeedsAttach(false);
+                }
+            }
+        }
+    }
+
     @Override @Nullable
     public Activity getActivity() {
         return hostController != null ? hostController.getActivity() : null;
     }
 
     @Override
-    public void onActivityDestroyed(@NonNull Activity activity) {
-        super.onActivityDestroyed(activity);
+    public void onActivityDestroyed(@NonNull Activity activity, boolean isConfigurationChange) {
+        super.onActivityDestroyed(activity, isConfigurationChange);
 
         removeHost();
     }
@@ -183,7 +217,7 @@ class ControllerHostedRouter extends Router {
 
     @Override
     boolean hasHost() {
-        return hostController != null;
+        return hostController != null && container != null;
     }
 
     @Override
@@ -191,6 +225,7 @@ class ControllerHostedRouter extends Router {
         super.saveInstanceState(outState);
 
         outState.putInt(KEY_HOST_ID, hostId);
+        outState.putBoolean(KEY_BOUND_TO_CONTAINER, boundToContainer);
         outState.putString(KEY_TAG, tag);
     }
 
@@ -199,22 +234,32 @@ class ControllerHostedRouter extends Router {
         super.restoreInstanceState(savedInstanceState);
 
         hostId = savedInstanceState.getInt(KEY_HOST_ID);
+        boundToContainer = savedInstanceState.getBoolean(KEY_BOUND_TO_CONTAINER);
         tag = savedInstanceState.getString(KEY_TAG);
     }
 
     @Override
-    void setControllerRouter(@NonNull Controller controller) {
-        super.setControllerRouter(controller);
+    void setRouterOnController(@NonNull Controller controller) {
         controller.setParentController(hostController);
+        super.setRouterOnController(controller);
     }
 
     int getHostId() {
         return hostId;
     }
 
-    @Nullable
-    String getTag() {
-        return tag;
+    boolean matches(int hostId, @Nullable String tag) {
+        if (!boundToContainer && container == null) {
+            if (this.tag == null) {
+                throw new IllegalStateException("Host ID can't be variable with a null tag");
+            }
+            if (this.tag.equals(tag)) {
+                this.hostId = hostId;
+                return true;
+            }
+        }
+
+        return this.hostId == hostId && TextUtils.equals(tag, this.tag);
     }
 
     @Override @NonNull
@@ -234,8 +279,21 @@ class ControllerHostedRouter extends Router {
         }
     }
 
-    @Override @Nullable
+    @Override @NonNull
     TransactionIndexer getTransactionIndexer() {
-        return getRootRouter().getTransactionIndexer();
+        Router rootRouter = getRootRouter();
+        if (rootRouter == this) {
+            String debugInfo;
+            if (hostController != null) {
+                debugInfo = String.format(Locale.ENGLISH, "%s (attached? %b, destroyed? %b, parent: %s)",
+                        hostController.getClass().getSimpleName(), hostController.isAttached(), hostController.isBeingDestroyed, hostController.getParentController());
+            } else {
+                debugInfo = "null host controller";
+            }
+            throw new IllegalStateException("Unable to retrieve TransactionIndexer from " + debugInfo);
+        } else {
+            return getRootRouter().getTransactionIndexer();
+        }
     }
+
 }

conductor/src/main/java/com/bluelinelabs/conductor/RestoreViewOnCreateController.java

@@ -1,53 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.LayoutInflater;
-import android.view.View;
-import android.view.ViewGroup;
-
-/**
- * A simple controller subclass that changes the onCreateView signature to include a saved view state parameter.
- * This is necessary for some third party libraries like Google Maps, which require passing in a saved state
- * bundle at the time of creation.
- */
-abstract public class RestoreViewOnCreateController extends Controller {
-
-    /**
-     * Convenience constructor for use when no arguments are needed.
-     */
-    protected RestoreViewOnCreateController() {
-        super(null);
-    }
-
-    /**
-     * Constructor that takes arguments that need to be retained across restarts.
-     *
-     * @param args Any arguments that need to be retained.
-     */
-    protected RestoreViewOnCreateController(@Nullable Bundle args) {
-        super(args);
-    }
-
-    @Override @NonNull
-    protected final View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container) {
-        return onCreateView(inflater, container, viewState == null ? null : viewState.getBundle(KEY_VIEW_STATE_BUNDLE));
-    }
-
-    /**
-     * Called when the controller is ready to display its view. A valid view must be returned. The standard body
-     * for this method will be {@code return inflater.inflate(R.layout.my_layout, container, false);}, plus
-     * any binding and state restoration code.
-     *
-     * @param inflater       The LayoutInflater that should be used to inflate views
-     * @param container      The parent view that this Controller's view will eventually be attached to.
-     *                       This Controller's view should NOT be added in this method. It is simply passed in
-     *                       so that valid LayoutParams can be used during inflation.
-     * @param savedViewState A bundle for the view's state, which would have been created in {@link #onSaveViewState(View, Bundle)},
-     *                       or {@code null} if no saved state exists.
-     */
-    @NonNull
-    protected abstract View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container, @Nullable Bundle savedViewState);
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/Router.java

@@ -1,19 +1,23 @@
 package com.bluelinelabs.conductor;
 
 import android.app.Activity;
+import android.content.Context;
 import android.content.Intent;
 import android.content.IntentSender;
 import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.support.annotation.UiThread;
+import android.util.Log;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 
-import com.bluelinelabs.conductor.Controller.LifecycleListener;
+import androidx.activity.ComponentActivity;
+import androidx.activity.OnBackPressedDispatcher;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.UiThread;
+
 import com.bluelinelabs.conductor.ControllerChangeHandler.ChangeTransaction;
 import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener;
 import com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler;
@@ -33,19 +37,39 @@ import java.util.List;
  */
 public abstract class Router {
 
+    private static final String TAG = "Conductor";
     private static final String KEY_BACKSTACK = "Router.backstack";
-    private static final String KEY_POPS_LAST_VIEW = "Router.popsLastView";
+    private static final String KEY_POP_ROOT_CONTROLLER_MODE = "Router.popRootControllerMode";
+    private static final String KEY_ON_BACK_PRESSED_DISPATCHER_ENABLED = "Router.onBackPressedDispatcherEnabled";
 
     final Backstack backstack = new Backstack();
     private final List<ControllerChangeListener> changeListeners = new ArrayList<>();
     private final List<ChangeTransaction> pendingControllerChanges = new ArrayList<>();
     final List<Controller> destroyingControllers = new ArrayList<>();
 
-    private boolean popsLastView = false;
+    PopRootControllerMode popRootControllerMode;
+    boolean onBackPressedDispatcherEnabled;
     boolean containerFullyAttached = false;
+    boolean isActivityStopped = false;
 
     ViewGroup container;
 
+    Router() {
+        backstack.setOnBackstackUpdatedListener(() -> {
+            if (!onBackPressedDispatcherEnabled) {
+                return;
+            }
+
+            Iterator<RouterTransaction> iterator = getBackstack().iterator();
+            int index = 0;
+            while (iterator.hasNext()) {
+                iterator.next().controller().onBackPressedCallback.setEnabled(
+                        index++ > 0 || popRootControllerMode != PopRootControllerMode.NEVER
+                );
+            }
+        });
+    }
+
     /**
      * Returns this Router's host Activity or {@code null} if it has either not yet been attached to
      * an Activity or if the Activity has been destroyed.
@@ -63,6 +87,22 @@ public abstract class Router {
      */
     public abstract void onActivityResult(int requestCode, int resultCode, @Nullable Intent data);
 
+    /**
+     * Returns the OnBackPressedDispatcher for this Router's host Activity or {@code null} if:
+     *   - This Router has not yet been attached to an Activity
+     *   - The attached Activity does not extend ComponentActivity
+     *   - The Activity has been destroyed
+     */
+    @Nullable
+    public OnBackPressedDispatcher getOnBackPressedDispatcher() {
+        Activity activity = getActivity();
+        if (activity instanceof ComponentActivity) {
+            return ((ComponentActivity) activity).getOnBackPressedDispatcher();
+        }
+
+        return null;
+    }
+
     /**
      * This should be called by the host Activity when its onRequestPermissionsResult method is called. The call will be forwarded
      * to the {@link Controller} with the instanceId passed in.
@@ -83,17 +123,25 @@ public abstract class Router {
      * This should be called by the host Activity when its onBackPressed method is called. The call will be forwarded
      * to its top {@link Controller}. If that controller doesn't handle it, then it will be popped.
      *
+     * Note: This method has been deprecated and should be replaced with registering OnBackPressedCallbacks with
+     * Controller instances.
+     *
      * @return Whether or not a back action was handled by the Router
      */
     @UiThread
+    @Deprecated
     public boolean handleBack() {
         ThreadUtils.ensureMainThread();
 
+        return handleBackDispatch();
+    }
+
+    protected boolean handleBackDispatch() {
         if (!backstack.isEmpty()) {
             //noinspection ConstantConditions
-            if (backstack.peek().controller.handleBack()) {
+            if (backstack.peek().controller().handleBack()) {
                 return true;
-            } else if (popCurrentController()) {
+            } else if ((backstack.getSize() > 1 || popRootControllerMode != PopRootControllerMode.NEVER) && popCurrentController()) {
                 return true;
             }
         }
@@ -115,7 +163,7 @@ public abstract class Router {
         if (transaction == null) {
             throw new IllegalStateException("Trying to pop the current controller when there are none on the backstack.");
         }
-        return popController(transaction.controller);
+        return popController(transaction.controller());
     }
 
     /**
@@ -129,7 +177,7 @@ public abstract class Router {
         ThreadUtils.ensureMainThread();
 
         RouterTransaction topTransaction = backstack.peek();
-        boolean poppingTopController = topTransaction != null && topTransaction.controller == controller;
+        boolean poppingTopController = topTransaction != null && topTransaction.controller() == controller;
 
         if (poppingTopController) {
             trackDestroyingController(backstack.pop());
@@ -137,15 +185,18 @@ public abstract class Router {
         } else {
             RouterTransaction removedTransaction = null;
             RouterTransaction nextTransaction = null;
-            for (RouterTransaction transaction : backstack) {
-                if (transaction.controller == controller) {
-                    if (controller.isAttached()) {
-                        trackDestroyingController(transaction);
-                    }
+            Iterator<RouterTransaction> iterator = backstack.iterator();
+            ControllerChangeHandler topPushHandler = topTransaction != null ? topTransaction.pushChangeHandler() : null;
+            final boolean needsNextTransactionAttach = topPushHandler != null ? !topPushHandler.getRemovesFromViewOnPush() : false;
+
+            while (iterator.hasNext()) {
+                RouterTransaction transaction = iterator.next();
+                if (transaction.controller() == controller) {
+                    trackDestroyingController(transaction);
                     backstack.remove(transaction);
                     removedTransaction = transaction;
                 } else if (removedTransaction != null) {
-                    if (!transaction.controller.isAttached()) {
+                    if (needsNextTransactionAttach && !transaction.controller().isAttached()) {
                         nextTransaction = transaction;
                     }
                     break;
@@ -157,7 +208,7 @@ public abstract class Router {
             }
         }
 
-        if (popsLastView) {
+        if (popRootControllerMode == PopRootControllerMode.POP_ROOT_CONTROLLER_AND_VIEW) {
             return topTransaction != null;
         } else {
             return !backstack.isEmpty();
@@ -198,10 +249,10 @@ public abstract class Router {
         final ControllerChangeHandler handler = transaction.pushChangeHandler();
         if (topTransaction != null) {
             //noinspection ConstantConditions
-            final boolean oldHandlerRemovedViews = topTransaction.pushChangeHandler() == null || topTransaction.pushChangeHandler().removesFromViewOnPush();
-            final boolean newHandlerRemovesViews = handler == null || handler.removesFromViewOnPush();
+            final boolean oldHandlerRemovedViews = topTransaction.pushChangeHandler() == null || topTransaction.pushChangeHandler().getRemovesFromViewOnPush();
+            final boolean newHandlerRemovesViews = handler == null || handler.getRemovesFromViewOnPush();
             if (!oldHandlerRemovedViews && newHandlerRemovesViews) {
-                for (RouterTransaction visibleTransaction : getVisibleTransactions(backstack.iterator())) {
+                for (RouterTransaction visibleTransaction : getVisibleTransactions(backstack.iterator(), true)) {
                     performControllerChange(null, visibleTransaction, true, handler);
                 }
             }
@@ -216,13 +267,14 @@ public abstract class Router {
     }
 
     void destroy(boolean popViews) {
-        popsLastView = true;
+        popRootControllerMode = PopRootControllerMode.POP_ROOT_CONTROLLER_AND_VIEW;
         final List<RouterTransaction> poppedControllers = backstack.popAll();
         trackDestroyingControllers(poppedControllers);
 
+        RouterTransaction topTransaction = null;
         if (popViews && poppedControllers.size() > 0) {
-            RouterTransaction topTransaction = poppedControllers.get(0);
-            topTransaction.controller().addLifecycleListener(new LifecycleListener() {
+            topTransaction = poppedControllers.get(0);
+            topTransaction.controller().addLifecycleListener(new Controller.LifecycleListener() {
                 @Override
                 public void onChangeEnd(@NonNull Controller controller, @NonNull ControllerChangeHandler changeHandler, @NonNull ControllerChangeType changeType) {
                     if (changeType == ControllerChangeType.POP_EXIT) {
@@ -236,6 +288,16 @@ public abstract class Router {
 
             performControllerChange(null, topTransaction, false, topTransaction.popChangeHandler());
         }
+
+        if (poppedControllers.size() > 0) {
+            NoOpControllerChangeHandler changeHandler = new NoOpControllerChangeHandler();
+            for (RouterTransaction routerTransaction : poppedControllers) {
+                if (routerTransaction != topTransaction) {
+                    routerTransaction.controller().changeStarted(changeHandler, ControllerChangeType.POP_EXIT);
+                    routerTransaction.controller().changeEnded(changeHandler, ControllerChangeType.POP_EXIT);
+                }
+            }
+        }
     }
 
     public int getContainerId() {
@@ -246,10 +308,33 @@ public abstract class Router {
      * If set to true, this router will handle back presses by performing a change handler on the last controller and view
      * in the stack. This defaults to false so that the developer can either finish its containing Activity or otherwise
      * hide its parent view without any strange artifacting.
+     *
+     * Note: This method has been deprecated and should be replaced with setPopRootControllerMode.
      */
     @NonNull
+    @Deprecated
     public Router setPopsLastView(boolean popsLastView) {
-        this.popsLastView = popsLastView;
+        this.popRootControllerMode = popsLastView ? PopRootControllerMode.POP_ROOT_CONTROLLER_AND_VIEW : PopRootControllerMode.POP_ROOT_CONTROLLER_BUT_NOT_VIEW;
+        return this;
+    }
+
+    /**
+     * Sets the method this router will use to handle back presses when there is only one controller left in the backstack.
+     * Defaults to POP_ROOT_CONTROLLER_BUT_NOT_VIEW so that the developer can either finish its containing Activity or
+     * otherwise hide its parent view without any strange artifacting.
+     */
+    @NonNull
+    public Router setPopRootControllerMode(@NonNull PopRootControllerMode popRootControllerMode) {
+        this.popRootControllerMode = popRootControllerMode;
+        return this;
+    }
+
+    @NonNull
+    public Router setOnBackPressedDispatcherEnabled(boolean enabled) {
+        if (backstack.getSize() > 0 && enabled != onBackPressedDispatcherEnabled) {
+            Log.e(TAG, "setOnBackPressedDispatcherEnabled call ignored, as controllers with a different setting have already been pushed.");
+        }
+        onBackPressedDispatcherEnabled = enabled;
         return this;
     }
 
@@ -276,7 +361,7 @@ public abstract class Router {
     public boolean popToRoot(@Nullable ControllerChangeHandler changeHandler) {
         ThreadUtils.ensureMainThread();
 
-        if (backstack.size() > 1) {
+        if (backstack.getSize() > 1) {
             //noinspection ConstantConditions
             popToTransaction(backstack.root(), changeHandler);
             return true;
@@ -342,7 +427,7 @@ public abstract class Router {
     @Nullable
     public Controller getControllerWithInstanceId(@NonNull String instanceId) {
         for (RouterTransaction transaction : backstack) {
-            Controller controllerWithId = transaction.controller.findController(instanceId);
+            Controller controllerWithId = transaction.controller().findController(instanceId);
             if (controllerWithId != null) {
                 return controllerWithId;
             }
@@ -360,7 +445,7 @@ public abstract class Router {
     public Controller getControllerWithTag(@NonNull String tag) {
         for (RouterTransaction transaction : backstack) {
             if (tag.equals(transaction.tag())) {
-                return transaction.controller;
+                return transaction.controller();
             }
         }
         return null;
@@ -371,7 +456,7 @@ public abstract class Router {
      */
     @SuppressWarnings("WeakerAccess")
     public int getBackstackSize() {
-        return backstack.size();
+        return backstack.getSize();
     }
 
     /**
@@ -379,7 +464,7 @@ public abstract class Router {
      */
     @NonNull
     public List<RouterTransaction> getBackstack() {
-        List<RouterTransaction> list = new ArrayList<>();
+        List<RouterTransaction> list = new ArrayList<>(backstack.getSize());
         Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
         while (backstackIterator.hasNext()) {
             list.add(backstackIterator.next());
@@ -399,22 +484,45 @@ public abstract class Router {
     public void setBackstack(@NonNull List<RouterTransaction> newBackstack, @Nullable ControllerChangeHandler changeHandler) {
         ThreadUtils.ensureMainThread();
 
-        List<RouterTransaction> oldVisibleTransactions = getVisibleTransactions(backstack.iterator());
-
-        boolean newRootRequiresPush = !(newBackstack.size() > 0 && backstack.contains(newBackstack.get(0)));
+        List<RouterTransaction> oldTransactions = getBackstack();
+        List<RouterTransaction> oldVisibleTransactions = getVisibleTransactions(backstack.iterator(), false);
 
         removeAllExceptVisibleAndUnowned();
         ensureOrderedTransactionIndices(newBackstack);
+        ensureNoDuplicateControllers(newBackstack);
 
         backstack.setBackstack(newBackstack);
-        for (RouterTransaction transaction : backstack) {
+
+        List<RouterTransaction> transactionsToBeRemoved = new ArrayList<>();
+        for (RouterTransaction oldTransaction : oldTransactions) {
+            boolean contains = false;
+            for (RouterTransaction newTransaction : newBackstack) {
+                if (oldTransaction.controller() == newTransaction.controller()) {
+                    contains = true;
+                    break;
+                }
+            }
+
+            if (!contains) {
+                // Inform the controller that it will be destroyed soon
+                oldTransaction.controller().isBeingDestroyed = true;
+                transactionsToBeRemoved.add(oldTransaction);
+            }
+        }
+
+        // Ensure all new controllers have a valid router set
+        Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
+        while (backstackIterator.hasNext()) {
+            RouterTransaction transaction = backstackIterator.next();
             transaction.onAttachedToRouter();
+            setRouterOnController(transaction.controller());
         }
 
         if (newBackstack.size() > 0) {
             List<RouterTransaction> reverseNewBackstack = new ArrayList<>(newBackstack);
             Collections.reverse(reverseNewBackstack);
-            List<RouterTransaction> newVisibleTransactions = getVisibleTransactions(reverseNewBackstack.iterator());
+            List<RouterTransaction> newVisibleTransactions = getVisibleTransactions(reverseNewBackstack.iterator(), false);
+            boolean newRootRequiresPush = !(newVisibleTransactions.size() > 0 && oldTransactions.contains(newVisibleTransactions.get(0)));
 
             boolean visibleTransactionsChanged = !backstacksAreEqual(newVisibleTransactions, oldVisibleTransactions);
             if (visibleTransactionsChanged) {
@@ -422,10 +530,10 @@ public abstract class Router {
                 RouterTransaction newRootTransaction = newVisibleTransactions.get(0);
 
                 // Replace the old root with the new one
-                if (oldRootTransaction == null || oldRootTransaction.controller != newRootTransaction.controller) {
+                if (oldRootTransaction == null || oldRootTransaction.controller() != newRootTransaction.controller()) {
                     // Ensure the existing root controller is fully pushed to the view hierarchy
                     if (oldRootTransaction != null) {
-                        ControllerChangeHandler.completeHandlerImmediately(oldRootTransaction.controller.getInstanceId());
+                        ControllerChangeHandler.completeHandlerImmediately(oldRootTransaction.controller().getInstanceId());
                     }
                     performControllerChange(newRootTransaction, oldRootTransaction, newRootRequiresPush, changeHandler);
                 }
@@ -436,8 +544,11 @@ public abstract class Router {
                     if (!newVisibleTransactions.contains(transaction)) {
                         ControllerChangeHandler localHandler = changeHandler != null ? changeHandler.copy() : new SimpleSwapChangeHandler();
                         localHandler.setForceRemoveViewOnPush(true);
-                        ControllerChangeHandler.completeHandlerImmediately(transaction.controller.getInstanceId());
-                        performControllerChange(null, transaction, newRootRequiresPush, localHandler);
+                        ControllerChangeHandler.completeHandlerImmediately(transaction.controller().getInstanceId());
+
+                        if (transaction.controller().view != null) {
+                            performControllerChange(null, transaction, newRootRequiresPush, localHandler);
+                        }
                     }
                 }
 
@@ -450,9 +561,31 @@ public abstract class Router {
                 }
             }
 
-            // Ensure all new controllers have a valid router set
-            for (RouterTransaction transaction : newBackstack) {
-                transaction.controller.setRouter(this);
+        } else {
+            // Remove all visible controllers that were previously on the backstack
+            for (int i = oldVisibleTransactions.size() - 1; i >= 0; i--) {
+                RouterTransaction transaction = oldVisibleTransactions.get(i);
+                ControllerChangeHandler localHandler = changeHandler != null ? changeHandler.copy() : new SimpleSwapChangeHandler();
+                ControllerChangeHandler.completeHandlerImmediately(transaction.controller().getInstanceId());
+                performControllerChange(null, transaction, false, localHandler);
+            }
+        }
+
+        // Destroy all old controllers that are no longer on the backstack. We don't do this when we initially
+        // set the backstack to prevent the possibility that they'll be destroyed before the controller
+        // change handler runs.
+        for (RouterTransaction removedTransaction : transactionsToBeRemoved) {
+
+            // Still need to ensure the controller isn't queued up to be removed later on.
+            boolean willBeRemoved = false;
+            for (ChangeTransaction pendingTransaction : pendingControllerChanges) {
+                if (pendingTransaction.from == removedTransaction.controller()) {
+                    willBeRemoved = true;
+                }
+            }
+
+            if (!willBeRemoved) {
+                removedTransaction.controller().destroy();
             }
         }
     }
@@ -493,12 +626,13 @@ public abstract class Router {
     public void rebindIfNeeded() {
         ThreadUtils.ensureMainThread();
 
-        Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
-        while (backstackIterator.hasNext()) {
-            RouterTransaction transaction = backstackIterator.next();
-
-            if (transaction.controller.getNeedsAttach()) {
+        // Not directly using the iterator in order to prevent ConcurrentModificationExceptions if controllers pop
+        // themselves on re-attach.
+        for (RouterTransaction transaction : getTransactions()) {
+            if (transaction.controller().getNeedsAttach()) {
                 performControllerChange(transaction, null, true, new SimpleSwapChangeHandler(false));
+            } else {
+                setRouterOnController(transaction.controller());
             }
         }
     }
@@ -511,10 +645,12 @@ public abstract class Router {
     }
 
     public final void onActivityStarted(@NonNull Activity activity) {
-        for (RouterTransaction transaction : backstack) {
-            transaction.controller.activityStarted(activity);
+        isActivityStopped = false;
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+        for (RouterTransaction transaction : backstack) {
+            transaction.controller().activityStarted(activity);
+
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onActivityStarted(activity);
             }
         }
@@ -522,9 +658,9 @@ public abstract class Router {
 
     public final void onActivityResumed(@NonNull Activity activity) {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.activityResumed(activity);
+            transaction.controller().activityResumed(activity);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onActivityResumed(activity);
             }
         }
@@ -532,9 +668,9 @@ public abstract class Router {
 
     public final void onActivityPaused(@NonNull Activity activity) {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.activityPaused(activity);
+            transaction.controller().activityPaused(activity);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onActivityPaused(activity);
             }
         }
@@ -542,23 +678,25 @@ public abstract class Router {
 
     public final void onActivityStopped(@NonNull Activity activity) {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.activityStopped(activity);
+            transaction.controller().activityStopped(activity);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onActivityStopped(activity);
             }
         }
+
+        isActivityStopped = true;
     }
 
-    public void onActivityDestroyed(@NonNull Activity activity) {
+    public void onActivityDestroyed(@NonNull Activity activity, boolean isConfigurationChange) {
         prepareForContainerRemoval();
         changeListeners.clear();
 
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.activityDestroyed(activity);
+            transaction.controller().activityDestroyed(activity);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
-                childRouter.onActivityDestroyed(activity);
+            for (Router childRouter : transaction.controller().getChildRouters()) {
+                childRouter.onActivityDestroyed(activity, isConfigurationChange);
             }
         }
 
@@ -567,49 +705,52 @@ public abstract class Router {
             controller.activityDestroyed(activity);
 
             for (Router childRouter : controller.getChildRouters()) {
-                childRouter.onActivityDestroyed(activity);
+                childRouter.onActivityDestroyed(activity, isConfigurationChange);
             }
         }
 
         container = null;
     }
 
-    void prepareForHostDetach() {
+    public void prepareForHostDetach() {
+        pendingControllerChanges.clear(); // rely on backstack based restoration in rebindIfNeeded
+
         for (RouterTransaction transaction : backstack) {
-            if (ControllerChangeHandler.completeHandlerImmediately(transaction.controller.getInstanceId())) {
-                transaction.controller.setNeedsAttach(true);
+            if (ControllerChangeHandler.completeHandlerImmediately(transaction.controller().getInstanceId())) {
+                transaction.controller().setNeedsAttach(true);
             }
-            transaction.controller.prepareForHostDetach();
+
+            transaction.controller().prepareForHostDetach();
         }
     }
 
     public void saveInstanceState(@NonNull Bundle outState) {
-        prepareForHostDetach();
-
         Bundle backstackState = new Bundle();
         backstack.saveInstanceState(backstackState);
 
+        outState.putInt(KEY_POP_ROOT_CONTROLLER_MODE, popRootControllerMode.ordinal());
+        outState.putBoolean(KEY_ON_BACK_PRESSED_DISPATCHER_ENABLED, onBackPressedDispatcherEnabled);
         outState.putParcelable(KEY_BACKSTACK, backstackState);
-        outState.putBoolean(KEY_POPS_LAST_VIEW, popsLastView);
     }
 
     public void restoreInstanceState(@NonNull Bundle savedInstanceState) {
         Bundle backstackBundle = savedInstanceState.getParcelable(KEY_BACKSTACK);
         //noinspection ConstantConditions
+        popRootControllerMode = PopRootControllerMode.values()[savedInstanceState.getInt(KEY_POP_ROOT_CONTROLLER_MODE)];
+        onBackPressedDispatcherEnabled = savedInstanceState.getBoolean(KEY_ON_BACK_PRESSED_DISPATCHER_ENABLED);
         backstack.restoreInstanceState(backstackBundle);
-        popsLastView = savedInstanceState.getBoolean(KEY_POPS_LAST_VIEW);
 
         Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
         while (backstackIterator.hasNext()) {
-            setControllerRouter(backstackIterator.next().controller);
+            setRouterOnController(backstackIterator.next().controller());
         }
     }
 
     public final void onCreateOptionsMenu(@NonNull Menu menu, @NonNull MenuInflater inflater) {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.createOptionsMenu(menu, inflater);
+            transaction.controller().createOptionsMenu(menu, inflater);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onCreateOptionsMenu(menu, inflater);
             }
         }
@@ -617,9 +758,9 @@ public abstract class Router {
 
     public final void onPrepareOptionsMenu(@NonNull Menu menu) {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.prepareOptionsMenu(menu);
+            transaction.controller().prepareOptionsMenu(menu);
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 childRouter.onPrepareOptionsMenu(menu);
             }
         }
@@ -627,11 +768,11 @@ public abstract class Router {
 
     public final boolean onOptionsItemSelected(@NonNull MenuItem item) {
         for (RouterTransaction transaction : backstack) {
-            if (transaction.controller.optionsItemSelected(item)) {
+            if (transaction.controller().optionsItemSelected(item)) {
                 return true;
             }
 
-            for (Router childRouter : transaction.controller.getChildRouters()) {
+            for (Router childRouter : transaction.controller().getChildRouters()) {
                 if (childRouter.onOptionsItemSelected(item)) {
                     return true;
                 }
@@ -641,7 +782,7 @@ public abstract class Router {
     }
 
     private void popToTransaction(@NonNull RouterTransaction transaction, @Nullable ControllerChangeHandler changeHandler) {
-        if (backstack.size() > 0) {
+        if (backstack.getSize() > 0) {
             RouterTransaction topTransaction = backstack.peek();
 
             List<RouterTransaction> updatedBackstack = new ArrayList<>();
@@ -663,11 +804,43 @@ public abstract class Router {
         }
     }
 
+    @Nullable
+    ChangeTransaction popTransaction(@NonNull Controller controller) {
+        RouterTransaction from = null;
+        RouterTransaction to = null;
+
+        Iterator<RouterTransaction> iterator = backstack.iterator();
+        while (iterator.hasNext()) {
+            RouterTransaction transaction = iterator.next();
+            if (transaction.controller() == controller) {
+                from = transaction;
+                if (iterator.hasNext()) {
+                    to = iterator.next();
+                }
+                break;
+            }
+        }
+
+        if (from == null) {
+            return null;
+        }
+
+        return new ChangeTransaction(
+            to != null ? to.controller() : null,
+            from.controller(),
+            false,
+            container,
+            from.popChangeHandler(),
+            Collections.emptyList()
+        );
+    }
+
     void watchContainerAttach() {
         container.post(new Runnable() {
             @Override
             public void run() {
                 containerFullyAttached = true;
+                performPendingControllerChanges();
             }
         });
     }
@@ -682,33 +855,54 @@ public abstract class Router {
 
     void onContextAvailable() {
         for (RouterTransaction transaction : backstack) {
-            transaction.controller.onContextAvailable();
+            transaction.controller().onContextAvailable();
+        }
+    }
+
+    void onContextUnavailable(@NonNull Context context) {
+        for (RouterTransaction transaction : backstack) {
+            transaction.controller().onContextUnavailable(context);
+        }
+        for (Controller controller : destroyingControllers) {
+            controller.onContextUnavailable(context);
         }
     }
 
     @NonNull
     final List<Controller> getControllers() {
-        List<Controller> controllers = new ArrayList<>();
+        List<Controller> controllers = new ArrayList<>(backstack.getSize());
 
         Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
         while (backstackIterator.hasNext()) {
-            controllers.add(backstackIterator.next().controller);
+            controllers.add(backstackIterator.next().controller());
         }
 
         return controllers;
     }
 
+    @NonNull
+    final List<RouterTransaction> getTransactions() {
+        List<RouterTransaction> transactions = new ArrayList<>(backstack.getSize());
+
+        Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
+        while (backstackIterator.hasNext()) {
+            transactions.add(backstackIterator.next());
+        }
+
+        return transactions;
+    }
+
     @Nullable
     public final Boolean handleRequestedPermission(@NonNull String permission) {
         for (RouterTransaction transaction : backstack) {
-            if (transaction.controller.didRequestPermission(permission)) {
-                return transaction.controller.shouldShowRequestPermissionRationale(permission);
+            if (transaction.controller().didRequestPermission(permission)) {
+                return transaction.controller().shouldShowRequestPermissionRationale(permission);
             }
         }
         return null;
     }
 
-    private void performControllerChange(@Nullable RouterTransaction to, @Nullable RouterTransaction from, boolean isPush) {
+    void performControllerChange(@Nullable RouterTransaction to, @Nullable RouterTransaction from, boolean isPush) {
         if (isPush && to != null) {
             to.onAttachedToRouter();
         }
@@ -727,24 +921,32 @@ public abstract class Router {
     }
 
     private void performControllerChange(@Nullable RouterTransaction to, @Nullable RouterTransaction from, boolean isPush, @Nullable ControllerChangeHandler changeHandler) {
-        Controller toController = to != null ? to.controller : null;
-        Controller fromController = from != null ? from.controller : null;
+        Controller toController = to != null ? to.controller() : null;
+        Controller fromController = from != null ? from.controller() : null;
         boolean forceDetachDestroy = false;
 
         if (to != null) {
             to.ensureValidIndex(getTransactionIndexer());
-            setControllerRouter(toController);
-        } else if (backstack.size() == 0 && !popsLastView) {
+            setRouterOnController(toController);
+        } else if (backstack.getSize() == 0 && popRootControllerMode == PopRootControllerMode.POP_ROOT_CONTROLLER_BUT_NOT_VIEW) {
             // We're emptying out the backstack. Views get weird if you transition them out, so just no-op it. The host
             // Activity or controller should be handling this by finishing or at least hiding this view.
             changeHandler = new NoOpControllerChangeHandler();
             forceDetachDestroy = true;
+        } else if (!isPush && fromController != null && !fromController.isAttached()) {
+            // We're popping fromController from the middle of the backstack,
+            // need to do it immediately and destroy the controller
+            forceDetachDestroy = true;
         }
 
         performControllerChange(toController, fromController, isPush, changeHandler);
 
-        if (forceDetachDestroy && fromController != null && fromController.getView() != null) {
-            fromController.detach(fromController.getView(), true, false);
+        if (forceDetachDestroy && fromController != null) {
+            if (fromController.getView() != null) {
+                fromController.detach(fromController.getView(), true, false);
+            } else {
+                fromController.destroy();
+            }
         }
     }
 
@@ -753,23 +955,26 @@ public abstract class Router {
             throw new IllegalStateException("Trying to push a controller that has already been destroyed. (" + to.getClass().getSimpleName() + ")");
         }
 
-        final ChangeTransaction transaction = new ChangeTransaction(to, from, isPush, container, changeHandler, changeListeners);
+        final ChangeTransaction transaction = new ChangeTransaction(to, from, isPush, container, changeHandler, new ArrayList<>(changeListeners));
 
         if (pendingControllerChanges.size() > 0) {
             // If we already have changes queued up (awaiting full container attach), queue this one up as well so they don't happen
             // out of order.
+            if (to != null) {
+                to.setNeedsAttach(true);
+            }
             pendingControllerChanges.add(transaction);
-        } else if (from != null && (changeHandler == null || changeHandler.removesFromViewOnPush()) && !containerFullyAttached) {
+        } else if (from != null && (changeHandler == null || changeHandler.getRemovesFromViewOnPush()) && !containerFullyAttached) {
             // If the change handler will remove the from view, we have to make sure the container is fully attached first so we avoid NPEs
             // within ViewGroup (details on issue #287). Post this to the container to ensure the attach is complete before we try to remove
             // anything.
+            if (to != null) {
+                to.setNeedsAttach(true);
+            }
             pendingControllerChanges.add(transaction);
-            container.post(new Runnable() {
-                @Override
-                public void run() {
-                    performPendingControllerChanges();
-                }
-            });
+            if (container != null) {
+                container.post(this::performPendingControllerChanges);
+            }
         } else {
             ControllerChangeHandler.executeChange(transaction);
         }
@@ -785,14 +990,17 @@ public abstract class Router {
     }
 
     protected void pushToBackstack(@NonNull RouterTransaction entry) {
+        if (backstack.contains(entry.controller())) {
+            throw new IllegalStateException("Trying to push a controller that already exists on the backstack.");
+        }
         backstack.push(entry);
     }
 
     private void trackDestroyingController(@NonNull RouterTransaction transaction) {
-        if (!transaction.controller.isDestroyed()) {
-            destroyingControllers.add(transaction.controller);
+        if (!transaction.controller().isDestroyed()) {
+            destroyingControllers.add(transaction.controller());
 
-            transaction.controller.addLifecycleListener(new LifecycleListener() {
+            transaction.controller().addLifecycleListener(new Controller.LifecycleListener() {
                 @Override
                 public void postDestroy(@NonNull Controller controller) {
                     destroyingControllers.remove(controller);
@@ -810,9 +1018,9 @@ public abstract class Router {
     private void removeAllExceptVisibleAndUnowned() {
         List<View> views = new ArrayList<>();
 
-        for (RouterTransaction transaction : getVisibleTransactions(backstack.iterator())) {
-            if (transaction.controller.getView() != null) {
-                views.add(transaction.controller.getView());
+        for (RouterTransaction transaction : getVisibleTransactions(backstack.iterator(), false)) {
+            if (transaction.controller().getView() != null) {
+                views.add(transaction.controller().getView());
             }
         }
 
@@ -823,7 +1031,7 @@ public abstract class Router {
         }
 
         final int childCount = container.getChildCount();
-        for (int i = 0; i < childCount; i++) {
+        for (int i = childCount - 1; i >= 0; i--) {
             final View child = container.getChildAt(i);
             if (!views.contains(child)) {
                 container.removeView(child);
@@ -831,19 +1039,30 @@ public abstract class Router {
         }
     }
 
-    // Swap around transaction indicies to ensure they don't get thrown out of order by the
+    // Swap around transaction indices to ensure they don't get thrown out of order by the
     // developer rearranging the backstack at runtime.
     private void ensureOrderedTransactionIndices(List<RouterTransaction> backstack) {
-        List<Integer> indices = new ArrayList<>();
+        List<Integer> indices = new ArrayList<>(backstack.size());
         for (RouterTransaction transaction : backstack) {
             transaction.ensureValidIndex(getTransactionIndexer());
-            indices.add(transaction.transactionIndex);
+            indices.add(transaction.getTransactionIndex());
         }
 
         Collections.sort(indices);
 
         for (int i = 0; i < backstack.size(); i++) {
-            backstack.get(i).transactionIndex = indices.get(i);
+            backstack.get(i).setTransactionIndex(indices.get(i));
+        }
+    }
+
+    private void ensureNoDuplicateControllers(List<RouterTransaction> backstack) {
+        for (int i = 0; i < backstack.size(); i++) {
+            Controller controller = backstack.get(i).controller();
+            for (int j = i + 1; j < backstack.size(); j++) {
+                if (backstack.get(j).controller() == controller) {
+                    throw new IllegalStateException("Trying to push the same controller to the backstack more than once.");
+                }
+            }
         }
     }
 
@@ -859,14 +1078,20 @@ public abstract class Router {
         }
     }
 
-    private List<RouterTransaction> getVisibleTransactions(@NonNull Iterator<RouterTransaction> backstackIterator) {
+    private List<RouterTransaction> getVisibleTransactions(@NonNull Iterator<RouterTransaction> backstackIterator, boolean onlyTop) {
+        boolean visible = true;
+
         List<RouterTransaction> transactions = new ArrayList<>();
         while (backstackIterator.hasNext()) {
             RouterTransaction transaction = backstackIterator.next();
-            transactions.add(transaction);
 
-            //noinspection ConstantConditions
-            if (transaction.pushChangeHandler() == null || transaction.pushChangeHandler().removesFromViewOnPush()) {
+            if (visible) {
+                transactions.add(transaction);
+            }
+
+            visible = transaction.pushChangeHandler() != null && !transaction.pushChangeHandler().getRemovesFromViewOnPush();
+
+            if (onlyTop && !visible) {
                 break;
             }
         }
@@ -889,7 +1114,7 @@ public abstract class Router {
         return true;
     }
 
-    void setControllerRouter(@NonNull Controller controller) {
+    void setRouterOnController(@NonNull Controller controller) {
         controller.setRouter(this);
         controller.onContextAvailable();
     }
@@ -906,6 +1131,27 @@ public abstract class Router {
     abstract boolean hasHost();
     @NonNull abstract List<Router> getSiblingRouters();
     @NonNull abstract Router getRootRouter();
-    @Nullable abstract TransactionIndexer getTransactionIndexer();
+    @NonNull abstract TransactionIndexer getTransactionIndexer();
 
+    /**
+     * Defines the way a Router will handle back button or pop events when there is only one controller
+     * left in the backstack.
+     */
+    public enum PopRootControllerMode {
+        /**
+         * The Router will not pop the final controller left on the backstack when the back button is pressed
+         * or when pop events are called. This mode is the default for Activity-hosted routers.
+         */
+        NEVER,
+        /**
+         * The Router will pop the final controller, but will leave its view in the hierarchy. This is useful
+         * when the developer wishes to allow its containing Activity to finish or otherwise hide its parent
+         * view without any strange artifacting.
+         */
+        POP_ROOT_CONTROLLER_BUT_NOT_VIEW,
+        /**
+         * The Router will pop both the final controller as well as its view.
+         */
+        POP_ROOT_CONTROLLER_AND_VIEW
+    }
 }

conductor/src/main/java/com/bluelinelabs/conductor/RouterTransaction.java

@@ -1,143 +0,0 @@
-package com.bluelinelabs.conductor;
-
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-
-import com.bluelinelabs.conductor.internal.TransactionIndexer;
-
-/**
- * Metadata used for adding {@link Controller}s to a {@link Router}.
- */
-public class RouterTransaction {
-
-    private static int INVALID_INDEX = -1;
-
-    private static final String KEY_VIEW_CONTROLLER_BUNDLE = "RouterTransaction.controller.bundle";
-    private static final String KEY_PUSH_TRANSITION = "RouterTransaction.pushControllerChangeHandler";
-    private static final String KEY_POP_TRANSITION = "RouterTransaction.popControllerChangeHandler";
-    private static final String KEY_TAG = "RouterTransaction.tag";
-    private static final String KEY_INDEX = "RouterTransaction.transactionIndex";
-    private static final String KEY_ATTACHED_TO_ROUTER = "RouterTransaction.attachedToRouter";
-
-    @NonNull final Controller controller;
-    private String tag;
-
-    private ControllerChangeHandler pushControllerChangeHandler;
-    private ControllerChangeHandler popControllerChangeHandler;
-    private boolean attachedToRouter;
-    int transactionIndex = INVALID_INDEX;
-
-    @NonNull
-    public static RouterTransaction with(@NonNull Controller controller) {
-        return new RouterTransaction(controller);
-    }
-
-    private RouterTransaction(@NonNull Controller controller) {
-        this.controller = controller;
-    }
-
-    RouterTransaction(@NonNull Bundle bundle) {
-        controller = Controller.newInstance(bundle.getBundle(KEY_VIEW_CONTROLLER_BUNDLE));
-        pushControllerChangeHandler = ControllerChangeHandler.fromBundle(bundle.getBundle(KEY_PUSH_TRANSITION));
-        popControllerChangeHandler = ControllerChangeHandler.fromBundle(bundle.getBundle(KEY_POP_TRANSITION));
-        tag = bundle.getString(KEY_TAG);
-        transactionIndex = bundle.getInt(KEY_INDEX);
-        attachedToRouter = bundle.getBoolean(KEY_ATTACHED_TO_ROUTER);
-    }
-
-    void onAttachedToRouter() {
-        attachedToRouter = true;
-    }
-
-    @NonNull
-    public Controller controller() {
-        return controller;
-    }
-
-    @Nullable
-    public String tag() {
-        return tag;
-    }
-
-    @NonNull
-    public RouterTransaction tag(@Nullable String tag) {
-        if (!attachedToRouter) {
-            this.tag = tag;
-            return this;
-        } else {
-            throw new RuntimeException(getClass().getSimpleName() + "s can not be modified after being added to a Router.");
-        }
-    }
-
-    @Nullable
-    public ControllerChangeHandler pushChangeHandler() {
-        ControllerChangeHandler handler = controller.getOverriddenPushHandler();
-        if (handler == null) {
-            handler = pushControllerChangeHandler;
-        }
-        return handler;
-    }
-
-    @NonNull
-    public RouterTransaction pushChangeHandler(@Nullable ControllerChangeHandler handler) {
-        if (!attachedToRouter) {
-            pushControllerChangeHandler = handler;
-            return this;
-        } else {
-            throw new RuntimeException(getClass().getSimpleName() + "s can not be modified after being added to a Router.");
-        }
-    }
-
-    @Nullable
-    public ControllerChangeHandler popChangeHandler() {
-        ControllerChangeHandler handler = controller.getOverriddenPopHandler();
-        if (handler == null) {
-            handler = popControllerChangeHandler;
-        }
-        return handler;
-    }
-
-    @NonNull
-    public RouterTransaction popChangeHandler(@Nullable ControllerChangeHandler handler) {
-        if (!attachedToRouter) {
-            popControllerChangeHandler = handler;
-            return this;
-        } else {
-            throw new RuntimeException(getClass().getSimpleName() + "s can not be modified after being added to a Router.");
-        }
-    }
-
-    void ensureValidIndex(@Nullable TransactionIndexer indexer) {
-        if (indexer == null) {
-            throw new RuntimeException();
-        }
-        if (transactionIndex == INVALID_INDEX && indexer != null) {
-            transactionIndex = indexer.nextIndex();
-        }
-    }
-
-    /**
-     * Used to serialize this transaction into a Bundle
-     */
-    @NonNull
-    public Bundle saveInstanceState() {
-        Bundle bundle = new Bundle();
-
-        bundle.putBundle(KEY_VIEW_CONTROLLER_BUNDLE, controller.saveInstanceState());
-
-        if (pushControllerChangeHandler != null) {
-            bundle.putBundle(KEY_PUSH_TRANSITION, pushControllerChangeHandler.toBundle());
-        }
-        if (popControllerChangeHandler != null) {
-            bundle.putBundle(KEY_POP_TRANSITION, popControllerChangeHandler.toBundle());
-        }
-
-        bundle.putString(KEY_TAG, tag);
-        bundle.putInt(KEY_INDEX, transactionIndex);
-        bundle.putBoolean(KEY_ATTACHED_TO_ROUTER, attachedToRouter);
-
-        return bundle;
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/RouterTransaction.kt

@@ -0,0 +1,122 @@
+package com.bluelinelabs.conductor
+
+import android.os.Bundle
+import androidx.annotation.RestrictTo
+import androidx.annotation.RestrictTo.Scope.LIBRARY
+import com.bluelinelabs.conductor.internal.TransactionIndexer
+
+private const val INVALID_INDEX = -1
+private const val KEY_VIEW_CONTROLLER_BUNDLE = "RouterTransaction.controller.bundle"
+private const val KEY_PUSH_TRANSITION = "RouterTransaction.pushControllerChangeHandler"
+private const val KEY_POP_TRANSITION = "RouterTransaction.popControllerChangeHandler"
+private const val KEY_TAG = "RouterTransaction.tag"
+private const val KEY_INDEX = "RouterTransaction.transactionIndex"
+private const val KEY_ATTACHED_TO_ROUTER = "RouterTransaction.attachedToRouter"
+
+/**
+ * Metadata used for adding [Controller]s to a [Router].
+ */
+class RouterTransaction private constructor(
+  @get:JvmName("controller")
+  val controller: Controller,
+  private var tag: String? = null,
+  private var pushControllerChangeHandler: ControllerChangeHandler? = null,
+  private var popControllerChangeHandler: ControllerChangeHandler? = null,
+  private var attachedToRouter: Boolean = false,
+  @get:RestrictTo(LIBRARY)
+  @set:RestrictTo(LIBRARY)
+  var transactionIndex: Int = INVALID_INDEX
+) {
+
+  @RestrictTo(LIBRARY)
+  internal constructor(bundle: Bundle) : this(
+    controller = Controller.newInstance(bundle.getBundle(KEY_VIEW_CONTROLLER_BUNDLE)!!),
+    pushControllerChangeHandler = ControllerChangeHandler.fromBundle(
+      bundle.getBundle(
+        KEY_PUSH_TRANSITION
+      )
+    ),
+    popControllerChangeHandler = ControllerChangeHandler.fromBundle(
+      bundle.getBundle(
+        KEY_POP_TRANSITION
+      )
+    ),
+    tag = bundle.getString(KEY_TAG),
+    transactionIndex = bundle.getInt(KEY_INDEX),
+    attachedToRouter = bundle.getBoolean(KEY_ATTACHED_TO_ROUTER)
+  )
+
+  fun onAttachedToRouter() {
+    attachedToRouter = true
+  }
+
+  fun tag(): String? = tag
+
+  fun tag(tag: String?): RouterTransaction {
+    return if (!attachedToRouter) {
+      this.tag = tag
+      this
+    } else {
+      throw RuntimeException(javaClass.simpleName + "s can not be modified after being added to a Router.")
+    }
+  }
+
+  fun pushChangeHandler(): ControllerChangeHandler? {
+    return controller.overriddenPushHandler ?: pushControllerChangeHandler
+  }
+
+  fun pushChangeHandler(handler: ControllerChangeHandler?): RouterTransaction {
+    return if (!attachedToRouter) {
+      pushControllerChangeHandler = handler
+      this
+    } else {
+      throw RuntimeException("${javaClass.simpleName}s can not be modified after being added to a Router.")
+    }
+  }
+
+  fun popChangeHandler(): ControllerChangeHandler? {
+    return controller.overriddenPopHandler ?: popControllerChangeHandler
+  }
+
+  fun popChangeHandler(handler: ControllerChangeHandler?): RouterTransaction {
+    return if (!attachedToRouter) {
+      popControllerChangeHandler = handler
+      this
+    } else {
+      throw RuntimeException("${javaClass.simpleName}s can not be modified after being added to a Router.")
+    }
+  }
+
+  fun ensureValidIndex(indexer: TransactionIndexer) {
+    if (transactionIndex == INVALID_INDEX) {
+      transactionIndex = indexer.nextIndex()
+    }
+  }
+
+  /**
+   * Used to serialize this transaction into a Bundle
+   */
+  fun saveInstanceState(): Bundle = Bundle().apply {
+    putBundle(KEY_VIEW_CONTROLLER_BUNDLE, controller.saveInstanceState())
+    pushControllerChangeHandler?.let { putBundle(KEY_PUSH_TRANSITION, it.toBundle()) }
+    popControllerChangeHandler?.let { putBundle(KEY_POP_TRANSITION, it.toBundle()) }
+    putString(KEY_TAG, tag)
+    putInt(KEY_INDEX, transactionIndex)
+    putBoolean(KEY_ATTACHED_TO_ROUTER, attachedToRouter)
+  }
+
+  companion object {
+
+    @JvmStatic
+    fun with(controller: Controller): RouterTransaction = RouterTransaction(controller)
+  }
+}
+
+fun Controller.asTransaction(
+  popChangeHandler: ControllerChangeHandler? = null,
+  pushChangeHandler: ControllerChangeHandler? = null
+): RouterTransaction {
+  return RouterTransaction.with(this)
+    .pushChangeHandler(pushChangeHandler)
+    .popChangeHandler(popChangeHandler)
+}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/AnimatorChangeHandler.java

@@ -1,253 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.animation.Animator;
-import android.animation.Animator.AnimatorListener;
-import android.animation.AnimatorListenerAdapter;
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-import android.view.ViewTreeObserver;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * A base {@link ControllerChangeHandler} that facilitates using {@link android.animation.Animator}s to replace Controller Views
- */
-public abstract class AnimatorChangeHandler extends ControllerChangeHandler {
-
-    private static final String KEY_DURATION = "AnimatorChangeHandler.duration";
-    private static final String KEY_REMOVES_FROM_ON_PUSH = "AnimatorChangeHandler.removesFromViewOnPush";
-
-    @SuppressWarnings("WeakerAccess")
-    public static final long DEFAULT_ANIMATION_DURATION = -1;
-
-    private long animationDuration;
-    private boolean removesFromViewOnPush;
-    private boolean canceled;
-    private boolean needsImmediateCompletion;
-    private boolean completed;
-    private Animator animator;
-    private OnAnimationReadyOrAbortedListener onAnimationReadyOrAbortedListener;
-
-    @SuppressWarnings("WeakerAccess")
-    public AnimatorChangeHandler() {
-        this(DEFAULT_ANIMATION_DURATION, true);
-    }
-
-    @SuppressWarnings("WeakerAccess")
-    public AnimatorChangeHandler(boolean removesFromViewOnPush) {
-        this(DEFAULT_ANIMATION_DURATION, removesFromViewOnPush);
-    }
-
-    @SuppressWarnings("WeakerAccess")
-    public AnimatorChangeHandler(long duration) {
-        this(duration, true);
-    }
-
-    public AnimatorChangeHandler(long duration, boolean removesFromViewOnPush) {
-        animationDuration = duration;
-        this.removesFromViewOnPush = removesFromViewOnPush;
-    }
-
-    @Override
-    public void saveToBundle(@NonNull Bundle bundle) {
-        super.saveToBundle(bundle);
-        bundle.putLong(KEY_DURATION, animationDuration);
-        bundle.putBoolean(KEY_REMOVES_FROM_ON_PUSH, removesFromViewOnPush);
-    }
-
-    @Override
-    public void restoreFromBundle(@NonNull Bundle bundle) {
-        super.restoreFromBundle(bundle);
-        animationDuration = bundle.getLong(KEY_DURATION);
-        removesFromViewOnPush = bundle.getBoolean(KEY_REMOVES_FROM_ON_PUSH);
-    }
-
-    @Override
-    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) {
-        super.onAbortPush(newHandler, newTop);
-
-        canceled = true;
-        if (animator != null) {
-            animator.cancel();
-        } else if (onAnimationReadyOrAbortedListener != null) {
-            onAnimationReadyOrAbortedListener.onReadyOrAborted();
-        }
-    }
-
-    @Override
-    public void completeImmediately() {
-        super.completeImmediately();
-
-        needsImmediateCompletion = true;
-        if (animator != null) {
-            animator.end();
-        } else if (onAnimationReadyOrAbortedListener != null) {
-            onAnimationReadyOrAbortedListener.onReadyOrAborted();
-        }
-    }
-
-    public long getAnimationDuration() {
-        return animationDuration;
-    }
-
-    @Override
-    public boolean removesFromViewOnPush() {
-        return removesFromViewOnPush;
-    }
-
-    /**
-     * Should be overridden to return the Animator to use while replacing Views.
-     *
-     * @param container The container these Views are hosted in.
-     * @param from The previous View in the container or {@code null} if there was no Controller before this transition
-     * @param to The next View that should be put in the container or {@code null} if no Controller is being transitioned to
-     * @param isPush True if this is a push transaction, false if it's a pop.
-     * @param toAddedToContainer True if the "to" view was added to the container as a part of this ChangeHandler. False if it was already in the hierarchy.
-     */
-    @NonNull
-    protected abstract Animator getAnimator(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, boolean toAddedToContainer);
-
-    /**
-     * Will be called after the animation is complete to reset the View that was removed to its pre-animation state.
-     */
-    protected abstract void resetFromView(@NonNull View from);
-
-    @Override
-    public final void performChange(@NonNull final ViewGroup container, @Nullable final View from, @Nullable final View to, final boolean isPush, @NonNull final ControllerChangeCompletedListener changeListener) {
-        boolean readyToAnimate = true;
-        final boolean addingToView = to != null && to.getParent() == null;
-
-        if (addingToView) {
-            if (isPush || from == null) {
-                container.addView(to);
-            } else if (to.getParent() == null) {
-                container.addView(to, container.indexOfChild(from));
-            }
-
-            if (to.getWidth() <= 0 && to.getHeight() <= 0) {
-                readyToAnimate = false;
-                onAnimationReadyOrAbortedListener = new OnAnimationReadyOrAbortedListener(container, from, to, isPush, true, changeListener);
-                to.getViewTreeObserver().addOnPreDrawListener(onAnimationReadyOrAbortedListener);
-            }
-        }
-
-        if (readyToAnimate) {
-            performAnimation(container, from, to, isPush, addingToView, changeListener);
-        }
-    }
-
-    private void complete(@NonNull ControllerChangeCompletedListener changeListener, @Nullable AnimatorListener animatorListener) {
-        if (!completed) {
-            completed = true;
-            changeListener.onChangeCompleted();
-        }
-
-        if (animator != null) {
-            if (animatorListener != null) {
-                animator.removeListener(animatorListener);
-            }
-            animator.cancel();
-            animator = null;
-        }
-
-        onAnimationReadyOrAbortedListener = null;
-    }
-
-    private void performAnimation(@NonNull final ViewGroup container, @Nullable final View from, @Nullable final View to, final boolean isPush, final boolean toAddedToContainer, @NonNull final ControllerChangeCompletedListener changeListener) {
-        if (canceled) {
-            complete(changeListener, null);
-            return;
-        }
-        if (needsImmediateCompletion) {
-            if (from != null && (!isPush || removesFromViewOnPush)) {
-                container.removeView(from);
-            }
-            complete(changeListener, null);
-            if (isPush && from != null) {
-                resetFromView(from);
-            }
-            return;
-        }
-
-        animator = getAnimator(container, from, to, isPush, toAddedToContainer);
-
-        if (animationDuration > 0) {
-            animator.setDuration(animationDuration);
-        }
-
-        animator.addListener(new AnimatorListenerAdapter() {
-            @Override
-            public void onAnimationCancel(Animator animation) {
-                if (from != null && (!isPush || removesFromViewOnPush) && needsImmediateCompletion) {
-                    container.removeView(from);
-                }
-
-                complete(changeListener, this);
-            }
-
-            @Override
-            public void onAnimationEnd(Animator animation) {
-                if (!canceled && animator != null) {
-                    if (from != null && (!isPush || removesFromViewOnPush)) {
-                        container.removeView(from);
-                    }
-
-                    complete(changeListener, this);
-
-                    if (isPush && from != null) {
-                        resetFromView(from);
-                    }
-                }
-            }
-        });
-
-        animator.start();
-    }
-
-    private class OnAnimationReadyOrAbortedListener implements ViewTreeObserver.OnPreDrawListener {
-        @NonNull final ViewGroup container;
-        @Nullable final View from;
-        @Nullable final View to;
-        final boolean isPush;
-        final boolean addingToView;
-        @NonNull final ControllerChangeCompletedListener changeListener;
-        private boolean hasRun;
-
-        OnAnimationReadyOrAbortedListener(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, boolean addingToView, @NonNull ControllerChangeCompletedListener changeListener) {
-            this.container = container;
-            this.from = from;
-            this.to = to;
-            this.isPush = isPush;
-            this.addingToView = addingToView;
-            this.changeListener = changeListener;
-        }
-
-        @Override
-        public boolean onPreDraw() {
-            onReadyOrAborted();
-
-            return true;
-        }
-
-        void onReadyOrAborted() {
-            if (!hasRun) {
-                hasRun = true;
-
-                if (to != null) {
-                    final ViewTreeObserver observer = to.getViewTreeObserver();
-                    if (observer.isAlive()) {
-                        observer.removeOnPreDrawListener(this);
-                    }
-                }
-
-                performAnimation(container, from, to, isPush, addingToView, changeListener);
-            }
-        }
-
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/AnimatorChangeHandler.kt

@@ -0,0 +1,228 @@
+package com.bluelinelabs.conductor.changehandler
+
+import android.animation.Animator
+import android.animation.AnimatorListenerAdapter
+import android.os.Bundle
+import android.view.View
+import android.view.ViewGroup
+import android.view.ViewTreeObserver
+import com.bluelinelabs.conductor.Controller
+import com.bluelinelabs.conductor.ControllerChangeHandler
+
+/**
+ * A base [ControllerChangeHandler] that facilitates using [android.animation.Animator]s to replace Controller Views
+ */
+abstract class AnimatorChangeHandler @JvmOverloads constructor(
+  animationDuration: Long = DEFAULT_ANIMATION_DURATION,
+  removesFromViewOnPush: Boolean = true,
+) : ControllerChangeHandler() {
+
+  var animationDuration: Long = animationDuration
+    private set
+
+  private var canceled = false
+  private var needsImmediateCompletion = false
+  private var completed = false
+  private var animator: Animator? = null
+  private var onAnimationReadyOrAbortedListener: OnAnimationReadyOrAbortedListener? = null
+
+  private var _removesFromViewOnPush = removesFromViewOnPush
+  override val removesFromViewOnPush: Boolean
+    get() = _removesFromViewOnPush
+
+  constructor(removesFromViewOnPush: Boolean = true) : this(
+    animationDuration = DEFAULT_ANIMATION_DURATION,
+    removesFromViewOnPush = removesFromViewOnPush,
+  )
+
+  override fun saveToBundle(bundle: Bundle) {
+    super.saveToBundle(bundle)
+    bundle.putLong(KEY_DURATION, animationDuration)
+    bundle.putBoolean(KEY_REMOVES_FROM_ON_PUSH, removesFromViewOnPush)
+  }
+
+  override fun restoreFromBundle(bundle: Bundle) {
+    super.restoreFromBundle(bundle)
+    animationDuration = bundle.getLong(KEY_DURATION)
+    _removesFromViewOnPush = bundle.getBoolean(KEY_REMOVES_FROM_ON_PUSH)
+  }
+
+  override fun onAbortPush(newHandler: ControllerChangeHandler, newTop: Controller?) {
+    super.onAbortPush(newHandler, newTop)
+
+    canceled = true
+    if (animator != null) {
+      animator!!.cancel()
+    } else if (onAnimationReadyOrAbortedListener != null) {
+      onAnimationReadyOrAbortedListener!!.onReadyOrAborted()
+    }
+  }
+
+  override fun completeImmediately() {
+    super.completeImmediately()
+
+    needsImmediateCompletion = true
+    if (animator != null) {
+      animator!!.end()
+    } else if (onAnimationReadyOrAbortedListener != null) {
+      onAnimationReadyOrAbortedListener!!.onReadyOrAborted()
+    }
+  }
+
+  /**
+   * Should be overridden to return the Animator to use while replacing Views.
+   *
+   * @param container The container these Views are hosted in.
+   * @param from The previous View in the container or `null` if there was no Controller before this transition
+   * @param to The next View that should be put in the container or `null` if no Controller is being transitioned to
+   * @param isPush True if this is a push transaction, false if it's a pop.
+   * @param toAddedToContainer True if the "to" view was added to the container as a part of this ChangeHandler. False if it was already in the hierarchy.
+   */
+  protected abstract fun getAnimator(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    toAddedToContainer: Boolean,
+  ): Animator
+
+  /**
+   * Will be called after the animation is complete to reset the View that was removed to its pre-animation state.
+   */
+  protected abstract fun resetFromView(from: View)
+
+  override fun performChange(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    changeListener: ControllerChangeCompletedListener,
+  ) {
+    var readyToAnimate = true
+    val addingToView = to != null && to.parent == null
+
+    if (addingToView) {
+      if (isPush || from == null) {
+        container.addView(to)
+      } else if (to!!.parent == null) {
+        container.addView(to, container.indexOfChild(from))
+      }
+      if (to!!.width <= 0 && to.height <= 0) {
+        readyToAnimate = false
+        onAnimationReadyOrAbortedListener = OnAnimationReadyOrAbortedListener(container, from, to, isPush, true, changeListener)
+        to.viewTreeObserver.addOnPreDrawListener(onAnimationReadyOrAbortedListener)
+      }
+    }
+
+    if (readyToAnimate) {
+      performAnimation(container, from, to, isPush, addingToView, changeListener)
+    }
+  }
+
+  fun complete(changeListener: ControllerChangeCompletedListener, animatorListener: Animator.AnimatorListener?) {
+    if (!completed) {
+      completed = true
+      changeListener.onChangeCompleted()
+    }
+
+    if (animator != null) {
+      if (animatorListener != null) {
+        animator!!.removeListener(animatorListener)
+      }
+      animator!!.cancel()
+      animator = null
+    }
+
+    onAnimationReadyOrAbortedListener = null
+  }
+
+  fun performAnimation(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    toAddedToContainer: Boolean,
+    changeListener: ControllerChangeCompletedListener,
+  ) {
+    if (canceled) {
+      complete(changeListener, null)
+      return
+    }
+
+    if (needsImmediateCompletion) {
+      if (from != null && (!isPush || removesFromViewOnPush)) {
+        container.removeView(from)
+      }
+      complete(changeListener, null)
+      if (isPush && from != null) {
+        resetFromView(from)
+      }
+      return
+    }
+
+    animator = getAnimator(container, from, to, isPush, toAddedToContainer)
+    if (animationDuration > 0) {
+      animator!!.duration = animationDuration
+    }
+
+    animator!!.addListener(
+      object : AnimatorListenerAdapter() {
+        override fun onAnimationCancel(animation: Animator) {
+          from?.let { resetFromView(it) }
+          if (to != null && to.parent === container) {
+            container.removeView(to)
+          }
+          complete(changeListener, this)
+        }
+
+        override fun onAnimationEnd(animation: Animator) {
+          if (!canceled && animator != null) {
+            if (from != null && (!isPush || removesFromViewOnPush)) {
+              container.removeView(from)
+            }
+            complete(changeListener, this)
+            if (isPush && from != null) {
+              resetFromView(from)
+            }
+          }
+        }
+      },
+    )
+    animator!!.start()
+  }
+
+  private inner class OnAnimationReadyOrAbortedListener constructor(
+    val container: ViewGroup,
+    val from: View?,
+    val to: View?,
+    val isPush: Boolean,
+    val addingToView: Boolean,
+    val changeListener: ControllerChangeCompletedListener,
+  ) : ViewTreeObserver.OnPreDrawListener {
+
+    private var hasRun = false
+    override fun onPreDraw(): Boolean {
+      onReadyOrAborted()
+      return true
+    }
+
+    fun onReadyOrAborted() {
+      if (!hasRun) {
+        hasRun = true
+        if (to != null) {
+          val observer = to.viewTreeObserver
+          if (observer.isAlive) {
+            observer.removeOnPreDrawListener(this)
+          }
+        }
+        performAnimation(container, from, to, isPush, addingToView, changeListener)
+      }
+    }
+  }
+
+  companion object {
+    private const val KEY_DURATION = "AnimatorChangeHandler.duration"
+    private const val KEY_REMOVES_FROM_ON_PUSH = "AnimatorChangeHandler.removesFromViewOnPush"
+    const val DEFAULT_ANIMATION_DURATION: Long = -1
+  }
+}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/AutoTransitionChangeHandler.java

@@ -1,30 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.annotation.TargetApi;
-import android.os.Build;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.transition.AutoTransition;
-import android.transition.Transition;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * A change handler that will use an AutoTransition.
- */
-@TargetApi(Build.VERSION_CODES.LOLLIPOP)
-public class AutoTransitionChangeHandler extends TransitionChangeHandler {
-
-    @Override @NonNull
-    protected Transition getTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush) {
-        return new AutoTransition();
-    }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        return new AutoTransitionChangeHandler();
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/FadeChangeHandler.java

@@ -1,57 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.animation.Animator;
-import android.animation.AnimatorSet;
-import android.animation.ObjectAnimator;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * An {@link AnimatorChangeHandler} that will cross fade two views
- */
-public class FadeChangeHandler extends AnimatorChangeHandler {
-
-    public FadeChangeHandler() { }
-
-    public FadeChangeHandler(boolean removesFromViewOnPush) {
-        super(removesFromViewOnPush);
-    }
-
-    public FadeChangeHandler(long duration) {
-        super(duration);
-    }
-
-    public FadeChangeHandler(long duration, boolean removesFromViewOnPush) {
-        super(duration, removesFromViewOnPush);
-    }
-
-    @Override @NonNull
-    protected Animator getAnimator(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, boolean toAddedToContainer) {
-        AnimatorSet animator = new AnimatorSet();
-        if (to != null) {
-            float start = toAddedToContainer ? 0 : to.getAlpha();
-            animator.play(ObjectAnimator.ofFloat(to, View.ALPHA, start, 1));
-        }
-
-        if (from != null && (!isPush || removesFromViewOnPush())) {
-            animator.play(ObjectAnimator.ofFloat(from, View.ALPHA, 0));
-        }
-
-        return animator;
-    }
-
-    @Override
-    protected void resetFromView(@NonNull View from) {
-        from.setAlpha(1);
-    }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        return new FadeChangeHandler(getAnimationDuration(), removesFromViewOnPush());
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/FadeChangeHandler.kt

@@ -0,0 +1,42 @@
+package com.bluelinelabs.conductor.changehandler
+
+import android.animation.Animator
+import android.animation.AnimatorSet
+import android.animation.ObjectAnimator
+import android.view.View
+import android.view.ViewGroup
+import com.bluelinelabs.conductor.ControllerChangeHandler
+
+/**
+ * An [AnimatorChangeHandler] that will cross fade two views
+ */
+class FadeChangeHandler : AnimatorChangeHandler {
+  constructor() : super()
+  constructor(removesFromViewOnPush: Boolean) : super(removesFromViewOnPush)
+  constructor(duration: Long) : super(duration)
+  constructor(duration: Long, removesFromViewOnPush: Boolean) : super(duration, removesFromViewOnPush)
+
+  override fun getAnimator(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    toAddedToContainer: Boolean,
+  ): Animator {
+    val animator = AnimatorSet()
+    if (to != null) {
+      val start = if (toAddedToContainer) 0F else to.alpha
+      animator.play(ObjectAnimator.ofFloat(to, View.ALPHA, start, 1f))
+    }
+    if (from != null && (!isPush || removesFromViewOnPush)) {
+      animator.play(ObjectAnimator.ofFloat(from, View.ALPHA, 0f))
+    }
+    return animator
+  }
+
+  override fun resetFromView(from: View) {
+    from.alpha = 1f
+  }
+
+  override fun copy(): ControllerChangeHandler = FadeChangeHandler(animationDuration, removesFromViewOnPush)
+}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/HorizontalChangeHandler.java

@@ -1,67 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.animation.Animator;
-import android.animation.AnimatorSet;
-import android.animation.ObjectAnimator;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * An {@link AnimatorChangeHandler} that will slide the views left or right, depending on if it's a push or pop.
- */
-public class HorizontalChangeHandler extends AnimatorChangeHandler {
-
-    public HorizontalChangeHandler() { }
-
-    public HorizontalChangeHandler(boolean removesFromViewOnPush) {
-        super(removesFromViewOnPush);
-    }
-
-    public HorizontalChangeHandler(long duration) {
-        super(duration);
-    }
-
-    public HorizontalChangeHandler(long duration, boolean removesFromViewOnPush) {
-        super(duration, removesFromViewOnPush);
-    }
-
-    @Override @NonNull
-    protected Animator getAnimator(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, boolean toAddedToContainer) {
-        AnimatorSet animatorSet = new AnimatorSet();
-
-        if (isPush) {
-            if (from != null) {
-                animatorSet.play(ObjectAnimator.ofFloat(from, View.TRANSLATION_X, -from.getWidth()));
-            }
-            if (to != null) {
-                animatorSet.play(ObjectAnimator.ofFloat(to, View.TRANSLATION_X, to.getWidth(), 0));
-            }
-        } else {
-            if (from != null) {
-                animatorSet.play(ObjectAnimator.ofFloat(from, View.TRANSLATION_X, from.getWidth()));
-            }
-            if (to != null) {
-                // Allow this to have a nice transition when coming off an aborted push animation
-                float fromLeft = from != null ? from.getTranslationX() : 0;
-                animatorSet.play(ObjectAnimator.ofFloat(to, View.TRANSLATION_X, fromLeft - to.getWidth(), 0));
-            }
-        }
-
-        return animatorSet;
-    }
-
-    @Override
-    protected void resetFromView(@NonNull View from) {
-        from.setTranslationX(0);
-    }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        return new HorizontalChangeHandler(getAnimationDuration(), removesFromViewOnPush());
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/HorizontalChangeHandler.kt

@@ -0,0 +1,52 @@
+package com.bluelinelabs.conductor.changehandler
+
+import android.animation.Animator
+import android.animation.AnimatorSet
+import android.animation.ObjectAnimator
+import android.view.View
+import android.view.ViewGroup
+import com.bluelinelabs.conductor.ControllerChangeHandler
+
+/**
+ * An [AnimatorChangeHandler] that will slide the views left or right, depending on if it's a push or pop.
+ */
+class HorizontalChangeHandler : AnimatorChangeHandler {
+  constructor() : super()
+  constructor(removesFromViewOnPush: Boolean) : super(removesFromViewOnPush)
+  constructor(duration: Long) : super(duration)
+  constructor(duration: Long, removesFromViewOnPush: Boolean) : super(duration, removesFromViewOnPush)
+
+  override fun getAnimator(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    toAddedToContainer: Boolean,
+  ): Animator {
+    val animatorSet = AnimatorSet()
+    if (isPush) {
+      if (from != null) {
+        animatorSet.play(ObjectAnimator.ofFloat(from, View.TRANSLATION_X, -from.width.toFloat()))
+      }
+      if (to != null) {
+        animatorSet.play(ObjectAnimator.ofFloat(to, View.TRANSLATION_X, to.width.toFloat(), 0f))
+      }
+    } else {
+      if (from != null) {
+        animatorSet.play(ObjectAnimator.ofFloat(from, View.TRANSLATION_X, from.width.toFloat()))
+      }
+      if (to != null) {
+        // Allow this to have a nice transition when coming off an aborted push animation
+        val fromLeft = from?.translationX ?: 0F
+        animatorSet.play(ObjectAnimator.ofFloat(to, View.TRANSLATION_X, fromLeft - to.width, 0f))
+      }
+    }
+    return animatorSet
+  }
+
+  override fun resetFromView(from: View) {
+    from.translationX = 0f
+  }
+
+  override fun copy(): ControllerChangeHandler = HorizontalChangeHandler(animationDuration, removesFromViewOnPush)
+}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/SimpleSwapChangeHandler.java

@@ -1,115 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.View.OnAttachStateChangeListener;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * A {@link ControllerChangeHandler} that will instantly swap Views with no animations or transitions.
- */
-public class SimpleSwapChangeHandler extends ControllerChangeHandler implements OnAttachStateChangeListener {
-
-    private static final String KEY_REMOVES_FROM_ON_PUSH = "SimpleSwapChangeHandler.removesFromViewOnPush";
-
-    private boolean removesFromViewOnPush;
-
-    private boolean canceled;
-
-    private ViewGroup container;
-    private ControllerChangeCompletedListener changeListener;
-
-    public SimpleSwapChangeHandler() {
-        this(true);
-    }
-
-    public SimpleSwapChangeHandler(boolean removesFromViewOnPush) {
-        this.removesFromViewOnPush = removesFromViewOnPush;
-    }
-
-    @Override
-    public void saveToBundle(@NonNull Bundle bundle) {
-        super.saveToBundle(bundle);
-        bundle.putBoolean(KEY_REMOVES_FROM_ON_PUSH, removesFromViewOnPush);
-    }
-
-    @Override
-    public void restoreFromBundle(@NonNull Bundle bundle) {
-        super.restoreFromBundle(bundle);
-        removesFromViewOnPush = bundle.getBoolean(KEY_REMOVES_FROM_ON_PUSH);
-    }
-
-    @Override
-    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) {
-        super.onAbortPush(newHandler, newTop);
-
-        canceled = true;
-    }
-
-    @Override
-    public void completeImmediately() {
-        if (changeListener != null) {
-            changeListener.onChangeCompleted();
-            changeListener = null;
-
-            container.removeOnAttachStateChangeListener(this);
-            container = null;
-        }
-    }
-
-    @Override
-    public void performChange(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, @NonNull ControllerChangeCompletedListener changeListener) {
-        if (!canceled) {
-            if (from != null && (!isPush || removesFromViewOnPush)) {
-                container.removeView(from);
-            }
-
-            if (to != null && to.getParent() == null) {
-                container.addView(to);
-            }
-        }
-
-        if (container.getWindowToken() != null) {
-            changeListener.onChangeCompleted();
-        } else {
-            this.changeListener = changeListener;
-            this.container = container;
-            container.addOnAttachStateChangeListener(this);
-        }
-
-    }
-
-    @Override
-    public boolean removesFromViewOnPush() {
-        return removesFromViewOnPush;
-    }
-
-    @Override
-    public void onViewAttachedToWindow(@NonNull View v) {
-        v.removeOnAttachStateChangeListener(this);
-
-        if (changeListener != null) {
-            changeListener.onChangeCompleted();
-            changeListener = null;
-            container = null;
-        }
-    }
-
-    @Override
-    public void onViewDetachedFromWindow(@NonNull View v) { }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        return new SimpleSwapChangeHandler(removesFromViewOnPush());
-    }
-
-    @Override
-    public boolean isReusable() {
-        return true;
-    }
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/SimpleSwapChangeHandler.kt

@@ -0,0 +1,88 @@
+package com.bluelinelabs.conductor.changehandler
+
+import android.os.Bundle
+import android.view.View
+import android.view.ViewGroup
+import com.bluelinelabs.conductor.Controller
+import com.bluelinelabs.conductor.ControllerChangeHandler
+
+/**
+ * A [ControllerChangeHandler] that will instantly swap Views with no animations or transitions.
+ */
+class SimpleSwapChangeHandler @JvmOverloads constructor(
+  removesFromViewOnPush: Boolean = true,
+) : ControllerChangeHandler(), View.OnAttachStateChangeListener {
+
+  private var _removesFromViewOnPush = removesFromViewOnPush
+  override val removesFromViewOnPush: Boolean
+    get() = _removesFromViewOnPush
+
+  override val isReusable = true
+
+  private var canceled = false
+  private var container: ViewGroup? = null
+  private var changeListener: ControllerChangeCompletedListener? = null
+
+  override fun saveToBundle(bundle: Bundle) {
+    super.saveToBundle(bundle)
+    bundle.putBoolean(KEY_REMOVES_FROM_ON_PUSH, removesFromViewOnPush)
+  }
+
+  override fun restoreFromBundle(bundle: Bundle) {
+    super.restoreFromBundle(bundle)
+    _removesFromViewOnPush = bundle.getBoolean(KEY_REMOVES_FROM_ON_PUSH)
+  }
+
+  override fun onAbortPush(newHandler: ControllerChangeHandler, newTop: Controller?) {
+    super.onAbortPush(newHandler, newTop)
+    canceled = true
+  }
+
+  override fun completeImmediately() {
+    changeListener?.onChangeCompleted()
+    changeListener = null
+
+    container?.removeOnAttachStateChangeListener(this)
+    container = null
+  }
+
+  override fun performChange(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    changeListener: ControllerChangeCompletedListener,
+  ) {
+    if (canceled) return
+
+    if (from != null && (!isPush || removesFromViewOnPush)) {
+      container.removeView(from)
+    }
+    if (to != null && to.parent == null) {
+      container.addView(to)
+    }
+
+    if (container.windowToken != null) {
+      changeListener.onChangeCompleted()
+    } else {
+      this.changeListener = changeListener
+      this.container = container
+      container.addOnAttachStateChangeListener(this)
+    }
+  }
+
+  override fun onViewAttachedToWindow(v: View) {
+    v.removeOnAttachStateChangeListener(this)
+
+    changeListener?.onChangeCompleted()
+    changeListener = null
+    container?.removeOnAttachStateChangeListener(this)
+    container = null
+  }
+
+  override fun onViewDetachedFromWindow(v: View) = Unit
+
+  override fun copy(): ControllerChangeHandler = SimpleSwapChangeHandler(removesFromViewOnPush)
+}
+
+private const val KEY_REMOVES_FROM_ON_PUSH = "SimpleSwapChangeHandler.removesFromViewOnPush"

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/TransitionChangeHandlerCompat.java

@@ -1,97 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.os.Build;
-import android.os.Bundle;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-import com.bluelinelabs.conductor.internal.ClassUtils;
-
-/**
- * A base {@link ControllerChangeHandler} that facilitates using {@link android.transition.Transition}s to replace Controller Views.
- * If the target device is running on a version of Android that doesn't support transitions, a fallback {@link ControllerChangeHandler} will be used.
- */
-public class TransitionChangeHandlerCompat extends ControllerChangeHandler {
-
-    private static final String KEY_CHANGE_HANDLER_CLASS = "TransitionChangeHandlerCompat.changeHandler.class";
-    private static final String KEY_HANDLER_STATE = "TransitionChangeHandlerCompat.changeHandler.state";
-
-    private ControllerChangeHandler changeHandler;
-
-    public TransitionChangeHandlerCompat() { }
-
-    /**
-     * Constructor that takes a {@link TransitionChangeHandler} for use with compatible devices, as well as a fallback
-     * {@link ControllerChangeHandler} for use with older devices.
-     *
-     * @param transitionChangeHandler The change handler that will be used on API 21 and above
-     * @param fallbackChangeHandler The change handler that will be used on APIs below 21
-     */
-    public TransitionChangeHandlerCompat(@NonNull TransitionChangeHandler transitionChangeHandler, @NonNull ControllerChangeHandler fallbackChangeHandler) {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-            changeHandler = transitionChangeHandler;
-        } else {
-            changeHandler = fallbackChangeHandler;
-        }
-    }
-
-    @Override
-    public void performChange(@NonNull final ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, @NonNull final ControllerChangeCompletedListener changeListener) {
-        changeHandler.performChange(container, from, to, isPush, changeListener);
-    }
-
-    @Override
-    public void saveToBundle(@NonNull Bundle bundle) {
-        super.saveToBundle(bundle);
-
-        bundle.putString(KEY_CHANGE_HANDLER_CLASS, changeHandler.getClass().getName());
-
-        Bundle stateBundle = new Bundle();
-        changeHandler.saveToBundle(stateBundle);
-        bundle.putBundle(KEY_HANDLER_STATE, stateBundle);
-    }
-
-    @Override
-    public void restoreFromBundle(@NonNull Bundle bundle) {
-        super.restoreFromBundle(bundle);
-
-        String className = bundle.getString(KEY_CHANGE_HANDLER_CLASS);
-        changeHandler = ClassUtils.newInstance(className);
-        //noinspection ConstantConditions
-        changeHandler.restoreFromBundle(bundle.getBundle(KEY_HANDLER_STATE));
-    }
-
-    @Override
-    public boolean removesFromViewOnPush() {
-        return changeHandler.removesFromViewOnPush();
-    }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-            return new TransitionChangeHandlerCompat((TransitionChangeHandler)changeHandler.copy(), null);
-        } else {
-            return new TransitionChangeHandlerCompat(null, changeHandler.copy());
-        }
-    }
-
-    @Override
-    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) {
-        changeHandler.onAbortPush(newHandler, newTop);
-    }
-
-    @Override
-    public void completeImmediately() {
-        changeHandler.completeImmediately();
-    }
-
-    @Override
-    public void setForceRemoveViewOnPush(boolean force) {
-        changeHandler.setForceRemoveViewOnPush(force);
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/VerticalChangeHandler.java

@@ -1,59 +0,0 @@
-package com.bluelinelabs.conductor.changehandler;
-
-import android.animation.Animator;
-import android.animation.AnimatorSet;
-import android.animation.ObjectAnimator;
-import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
-import android.view.View;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- * An {@link AnimatorChangeHandler} that will slide either slide a new View up or slide an old View down,
- * depending on whether a push or pop change is happening.
- */
-public class VerticalChangeHandler extends AnimatorChangeHandler {
-
-    public VerticalChangeHandler() { }
-
-    public VerticalChangeHandler(boolean removesFromViewOnPush) {
-        super(removesFromViewOnPush);
-    }
-
-    public VerticalChangeHandler(long duration) {
-        super(duration);
-    }
-
-    public VerticalChangeHandler(long duration, boolean removesFromViewOnPush) {
-        super(duration, removesFromViewOnPush);
-    }
-
-    @Override @NonNull
-    protected Animator getAnimator(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush, boolean toAddedToContainer) {
-        AnimatorSet animator = new AnimatorSet();
-        List<Animator> viewAnimators = new ArrayList<>();
-
-        if (isPush && to != null) {
-            viewAnimators.add(ObjectAnimator.ofFloat(to, View.TRANSLATION_Y, to.getHeight(), 0));
-        } else if (!isPush && from != null) {
-            viewAnimators.add(ObjectAnimator.ofFloat(from, View.TRANSLATION_Y, from.getHeight()));
-        }
-
-        animator.playTogether(viewAnimators);
-        return animator;
-    }
-
-    @Override
-    protected void resetFromView(@NonNull View from) { }
-
-    @Override @NonNull
-    public ControllerChangeHandler copy() {
-        return new VerticalChangeHandler(getAnimationDuration(), removesFromViewOnPush());
-    }
-
-}

conductor/src/main/java/com/bluelinelabs/conductor/changehandler/VerticalChangeHandler.kt

@@ -0,0 +1,43 @@
+package com.bluelinelabs.conductor.changehandler
+
+import android.animation.Animator
+import android.animation.AnimatorSet
+import android.animation.ObjectAnimator
+import android.view.View
+import android.view.ViewGroup
+import com.bluelinelabs.conductor.ControllerChangeHandler
+
+/**
+ * An [AnimatorChangeHandler] that will slide either slide a new View up or slide an old View down,
+ * depending on whether a push or pop change is happening.
+ */
+class VerticalChangeHandler : AnimatorChangeHandler {
+  constructor() : super()
+  constructor(removesFromViewOnPush: Boolean) : super(removesFromViewOnPush)
+  constructor(duration: Long) : super(duration)
+  constructor(duration: Long, removesFromViewOnPush: Boolean) : super(duration, removesFromViewOnPush)
+
+  override fun getAnimator(
+    container: ViewGroup,
+    from: View?,
+    to: View?,
+    isPush: Boolean,
+    toAddedToContainer: Boolean,
+  ): Animator {
+    val animator = AnimatorSet()
+    val viewAnimators: MutableList<Animator> = ArrayList()
+
+    if (isPush && to != null) {
+      viewAnimators.add(ObjectAnimator.ofFloat(to, View.TRANSLATION_Y, to.height.toFloat(), 0f))
+    } else if (!isPush && from != null) {
+      viewAnimators.add(ObjectAnimator.ofFloat(from, View.TRANSLATION_Y, from.height.toFloat()))
+    }
+
+    animator.playTogether(viewAnimators)
+    return animator
+  }
+
+  override fun resetFromView(from: View) = Unit
+
+  override fun copy(): ControllerChangeHandler = VerticalChangeHandler(animationDuration, removesFromViewOnPush)
+}

conductor/src/main/java/com/bluelinelabs/conductor/internal/BackGestureViewState.kt

@@ -0,0 +1,15 @@
+package com.bluelinelabs.conductor.internal
+
+import android.view.View
+import com.bluelinelabs.conductor.Controller
+
+class BackGestureViewState(
+  val fromView: View,
+  val toViews: List<BackGestureControllerView>,
+)
+
+class BackGestureControllerView(
+  val controller: Controller,
+  val view: View,
+  val inflatedForGesture: Boolean,
+)