Version bump for 3.0.0 release

Fixes #481
Fixes #426
Fixes #407

.gitignore

@@ -35,6 +35,4 @@ pom.xml.*
 local.properties
 
 *.prefs
-
-# The keystore file
-app/spothero-release.keystore
+.DS_Store

.travis.yml

@@ -1,13 +1,10 @@
 language: android
 
-android:
-  components:
-    - tools
-    - build-tools-28.0.3
-    - android-28
-    - extra-android-m2repository
-  licenses:
-    - '.+'
+before_install:
+  - mkdir "$ANDROID_HOME/licenses" || true
+  - echo "\n24333f8a63b6825ea9c5514f83c2829b004d1fee" > "$ANDROID_HOME/licenses/android-sdk-license"
+  - echo "\n84831b9409646a918e30573bab4c9c91346d8abd" > "$ANDROID_HOME/licenses/android-sdk-preview-license"
+  - yes | sdkmanager --update
 
 script:
   - ./gradlew test

README.md

@@ -20,22 +20,25 @@ Conductor is architecture-agnostic and does not try to force any design decision
 ## Installation
 
 ```gradle
-implementation 'com.bluelinelabs:conductor:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor:3.0.0'
 
 // AndroidX Transition change handlers:
-implementation 'com.bluelinelabs:conductor-androidx-transition:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor-androidx-transition:3.0.0'
 
 // ViewPager PagerAdapter:
-implementation 'com.bluelinelabs:conductor-viewpager:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor-viewpager:3.0.0'
+
+// ViewPager2 Adapter:
+implementation 'com.bluelinelabs:conductor-viewpager2:3.0.0'
 
 // RxJava2 lifecycle support:
-implementation 'com.bluelinelabs:conductor-rxlifecycle2:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor-rxlifecycle2:3.0.0'
 
 // RxJava2 Autodispose support:
-implementation 'com.bluelinelabs:conductor-autodispose:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor-autodispose:3.0.0'
 
 // Lifecycle-aware Controllers (architecture components):
-implementation 'com.bluelinelabs:conductor-archlifecycle:3.0.0-rc5'
+implementation 'com.bluelinelabs:conductor-archlifecycle:3.0.0'
 ```
 
 **SNAPSHOT**

build.gradle

@@ -6,7 +6,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.3'
+        classpath "com.android.tools.build:gradle:$agpVersion"
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
         classpath "com.vanniktech:gradle-maven-publish-plugin:$mvnPublishVersion"
     }
@@ -15,27 +15,9 @@ buildscript {
 allprojects {
     repositories {
         mavenCentral()
-        maven { url 'https://maven.google.com' }
+        google()
         jcenter()
     }
-
-    plugins.withType(com.android.build.gradle.BasePlugin).configureEach { plugin ->
-        plugin.extension.compileOptions {
-            sourceCompatibility = JavaVersion.VERSION_1_8
-            targetCompatibility = JavaVersion.VERSION_1_8
-        }
-    }
-
-    tasks.withType(JavaCompile).configureEach { task ->
-        task.sourceCompatibility = JavaVersion.VERSION_1_8
-        task.targetCompatibility = JavaVersion.VERSION_1_8
-    }
-
-    tasks.withType(org.jetbrains.kotlin.gradle.dsl.KotlinJvmCompile).configureEach { task ->
-        task.kotlinOptions {
-            jvmTarget = "1.8"
-        }
-    }
 }
 
 apply from: rootProject.file('dependencies.gradle')

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

@@ -14,7 +14,6 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.uast.UClass;
 import org.jetbrains.uast.UElement;
 import org.jetbrains.uast.UMethod;
-import org.jetbrains.uast.UTypeReferenceExpression;
 
 import java.util.Collections;
 import java.util.List;
@@ -48,13 +47,7 @@ public final class ControllerChangeHandlerIssueDetector extends Detector impleme
                     return;
                 }
 
-                boolean hasSuperType = false;
-                for (UTypeReferenceExpression superType : node.getUastSuperTypes()) {
-                    if (CLASS_NAME.equals(superType.asRenderString())) {
-                        hasSuperType = true;
-                        break;
-                    }
-                }
+                final boolean hasSuperType = evaluator.extendsClass(node.getPsi(), CLASS_NAME, true);
                 if (!hasSuperType) {
                     return;
                 }

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

@@ -16,7 +16,6 @@ import org.jetbrains.uast.UClass;
 import org.jetbrains.uast.UElement;
 import org.jetbrains.uast.UMethod;
 import org.jetbrains.uast.UParameter;
-import org.jetbrains.uast.UTypeReferenceExpression;
 
 import java.util.Collections;
 import java.util.List;
@@ -35,7 +34,7 @@ public final class ControllerIssueDetector extends Detector implements Detector.
 
     @Override
     public List<Class<? extends UElement>> getApplicableUastTypes() {
-        return Collections.<Class<? extends UElement>>singletonList(UClass.class);
+        return Collections.singletonList(UClass.class);
     }
 
     @Override
@@ -49,13 +48,7 @@ public final class ControllerIssueDetector extends Detector implements Detector.
                     return;
                 }
 
-                boolean hasSuperType = false;
-                for (UTypeReferenceExpression superType : node.getUastSuperTypes()) {
-                    if (CLASS_NAME.equals(superType.asRenderString())) {
-                        hasSuperType = true;
-                        break;
-                    }
-                }
+                final boolean hasSuperType = evaluator.extendsClass(node.getPsi(), CLASS_NAME, true);
                 if (!hasSuperType) {
                     return;
                 }

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

@@ -1,24 +1,27 @@
 package com.bluelinelabs.conductor.lint;
 
+import com.android.tools.lint.checks.infrastructure.LintDetectorTest;
+
 import org.intellij.lang.annotations.Language;
 import org.junit.Test;
 
 import static com.android.tools.lint.checks.infrastructure.TestFiles.java;
 import static com.android.tools.lint.checks.infrastructure.TestLintTask.lint;
 
+@SuppressWarnings("UnstableApiUsage")
 public class ControllerChangeHandlerDetectorTest {
 
     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";
 
+    private final LintDetectorTest.TestFile controllerChangeHandlerStub = java(
+            "package com.bluelinelabs.conductor;\n"
+                    + "abstract class ControllerChangeHandler {}"
+    );
+
     @Test
     public void testWithNoConstructor() {
         @Language("JAVA") String source = ""
@@ -27,7 +30,7 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
@@ -42,7 +45,7 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
@@ -57,7 +60,7 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expect(CONSTRUCTOR);
@@ -73,7 +76,7 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
@@ -88,7 +91,7 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expect(CONSTRUCTOR);
@@ -103,10 +106,32 @@ public class ControllerChangeHandlerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerChangeHandlerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
-                .expect(PRIVATE_CLASS_ERROR);
+                .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");
     }
 
+    @Test
+    public void testWithPrivateClassOfBaseClass() {
+        @Language("JAVA") String baseClass = ""
+                + "package test;\n"
+                + "abstract class BaseChangeHandler extends com.bluelinelabs.conductor.ControllerChangeHandler {}";
+
+        @Language("JAVA") String source = ""
+                + "package test;\n"
+                + "private class SampleHandler extends test.BaseChangeHandler {}";
+
+        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

@@ -1,24 +1,33 @@
 package com.bluelinelabs.conductor.lint;
 
+import com.android.tools.lint.checks.infrastructure.LintDetectorTest;
+
 import org.intellij.lang.annotations.Language;
 import org.junit.Test;
 
 import static com.android.tools.lint.checks.infrastructure.TestFiles.java;
 import static com.android.tools.lint.checks.infrastructure.TestLintTask.lint;
 
+@SuppressWarnings("UnstableApiUsage")
 public class ControllerDetectorTest {
 
     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";
 
+    private final LintDetectorTest.TestFile controllerStub = java(
+            "package com.bluelinelabs.conductor;\n"
+                    + "abstract class Controller {}"
+    );
+
+
     @Test
     public void testWithNoConstructor() {
         @Language("JAVA") String source = ""
@@ -27,7 +36,7 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
@@ -42,7 +51,7 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
@@ -57,7 +66,7 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expect(CONSTRUCTOR_ERROR);
@@ -73,12 +82,38 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expectClean();
     }
 
+    @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 = ""
@@ -88,7 +123,7 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expect(CONSTRUCTOR_ERROR);
@@ -103,7 +138,7 @@ public class ControllerDetectorTest {
                 + "}";
 
         lint()
-                .files(java(source))
+                .files(controllerStub, java(source))
                 .issues(ControllerIssueDetector.ISSUE, ControllerChangeHandlerIssueDetector.ISSUE)
                 .run()
                 .expect(CLASS_ERROR);

conductor-modules/androidx-transition/gradle.properties

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

conductor-modules/transition-platform/gradle.properties

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

conductor-modules/transition-platform/src/main/AndroidManifest.xml

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

conductor-modules/transition-platform/src/main/java/com/bluelinelabs/conductor/changehandler/platformtransition/SharedElementTransitionChangeHandler.java

@@ -1,647 +0,0 @@
-package com.bluelinelabs.conductor.changehandler.platformtransition;
-
-import android.annotation.TargetApi;
-import android.app.SharedElementCallback;
-import android.graphics.Rect;
-import android.os.Build;
-import android.transition.Transition;
-import android.transition.Transition.TransitionListener;
-import android.transition.TransitionSet;
-import android.util.ArrayMap;
-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 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 Android's <b>platform</b> {@link Transition}. If you're using androidx transitions, consider
- * using the {@code SharedElementTransitionChangeHandler} provided by the {@code androidx-transitions} Conductor module.
- */
-// Much of this class is based on FragmentTransition.java and FragmentTransitionCompat21.java from the Android support library
-@TargetApi(Build.VERSION_CODES.LOLLIPOP)
-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 = () -> {
-            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();
-    }
-
-    @Override
-    protected void onEnd() {
-        exitTransition = null;
-        enterTransition = null;
-        sharedElementTransition = null;
-    }
-
-    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, () -> {
-                waitForTransitionNames.remove(view.getTransitionName());
-
-                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, () -> {
-            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, () -> {
-            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(removedView.view.getTransitionName(), 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(view.getTransitionName())) {
-                    String key = findKeyForValue(sharedElementNames, name);
-                    if (key != null) {
-                        sharedElementNames.put(key, view.getTransitionName());
-                    }
-                }
-            }
-        } 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(view.getTransitionName())) {
-                    String targetValue = sharedElementNames.remove(name);
-                    sharedElementNames.put(view.getTransitionName(), 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 (viewGroup.isTransitionGroup()) {
-                    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 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, () -> {
-            final int numSharedElements = toSharedElements.size();
-            for (int i = 0; i < numSharedElements; i++) {
-                View view = toSharedElements.get(i);
-                String name = view.getTransitionName();
-                if (name != null) {
-                    String inName = findKeyForValue(sharedElementNames, name);
-                    view.setTransitionName(inName);
-                }
-            }
-        });
-    }
-
-    private void scheduleNameReset(@NonNull final ViewGroup container, @NonNull final List<View> toSharedElements) {
-        OneShotPreDrawListener.add(true, container, () -> {
-            final int numSharedElements = toSharedElements.size();
-            for (int i = 0; i < numSharedElements; i++) {
-                final View view = toSharedElements.get(i);
-                final String name = view.getTransitionName();
-                final String inName = sharedElementNames.get(name);
-                view.setTransitionName(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 = sharedElement.getTransitionName();
-        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/transition-platform/src/main/java/com/bluelinelabs/conductor/changehandler/platformtransition/TransitionChangeHandler.java

@@ -1,149 +0,0 @@
-package com.bluelinelabs.conductor.changehandler.platformtransition;
-
-import android.annotation.TargetApi;
-import android.os.Build;
-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 com.bluelinelabs.conductor.Controller;
-import com.bluelinelabs.conductor.ControllerChangeHandler;
-
-/**
- * A base {@link ControllerChangeHandler} that facilitates using {@link Transition}s to replace Controller Views.
- * <p/>
- * Note that this class uses Android's <b>platform</b> {@link Transition}. If you're using androidx transitions, consider
- * using the {@code TransitionChangeHandler} provided by the {@code androidx-transitions} Conductor module.
- */
-@TargetApi(Build.VERSION_CODES.LOLLIPOP)
-public abstract class TransitionChangeHandler extends ControllerChangeHandler {
-
-    public interface OnTransitionPreparedListener {
-        void onPrepared();
-    }
-
-    boolean canceled;
-    private boolean needsImmediateCompletion;
-
-    /**
-     * Should be overridden to return the Transition 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
-     */
-    @NonNull
-    protected abstract Transition getTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, boolean isPush);
-
-    @Override
-    public void onAbortPush(@NonNull ControllerChangeHandler newHandler, @Nullable Controller newTop) {
-        super.onAbortPush(newHandler, newTop);
-
-        canceled = true;
-    }
-
-    @Override
-    public void completeImmediately() {
-        super.completeImmediately();
-
-        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;
-        }
-        if (needsImmediateCompletion) {
-            executePropertyChanges(container, from, to, null, isPush);
-            changeListener.onChangeCompleted();
-            return;
-        }
-
-        final Runnable onTransitionNotStarted = changeListener::onChangeCompleted;
-
-        final Transition transition = getTransition(container, from, to, isPush);
-        transition.addListener(new TransitionListener() {
-            @Override
-            public void onTransitionStart(Transition transition) {
-                container.removeCallbacks(onTransitionNotStarted);
-            }
-
-            @Override
-            public void onTransitionEnd(Transition transition) {
-                listener.onChangeCompleted();
-                listener = null;
-            }
-
-            @Override
-            public void onTransitionCancel(Transition transition) {
-                listener.onChangeCompleted();
-                listener = null;
-            }
-
-            @Override
-            public void onTransitionPause(Transition transition) { }
-
-            @Override
-            public void onTransitionResume(Transition transition) { }
-        });
-
-        prepareForTransition(container, from, to, transition, isPush, () -> {
-            if (!canceled) {
-                TransitionManager.beginDelayedTransition(container, transition);
-                executePropertyChanges(container, from, to, transition, isPush);
-                container.post(onTransitionNotStarted);
-            }
-        });
-    }
-
-    @Override
-    public boolean removesFromViewOnPush() {
-        return true;
-    }
-
-    /**
-     * Called before a transition occurs. This can be used to reorder views, set their transition names, etc. The transition will begin
-     * when {@code onTransitionPreparedListener} is called.
-     *
-     * @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 transition The transition that is being prepared for
-     * @param isPush     True if this is a push transaction, false if it's a pop
-     */
-    public void prepareForTransition(@NonNull ViewGroup container, @Nullable View from, @Nullable View to, @NonNull Transition transition, boolean isPush, @NonNull OnTransitionPreparedListener onTransitionPreparedListener) {
-        onTransitionPreparedListener.onPrepared();
-    }
-
-    /**
-     * This should set all view properties needed for the transition to work properly. By default it removes the "from" view
-     * and adds the "to" view.
-     *
-     * @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 transition The transition with which {@code TransitionManager.beginDelayedTransition} has been called. This will be null only if another ControllerChangeHandler immediately overrides this one.
-     * @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) {
-            container.removeView(from);
-        }
-        if (to != null && to.getParent() == null) {
-            container.addView(to);
-        }
-    }
-
-}

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

@@ -1,184 +0,0 @@
-package com.bluelinelabs.conductor.internal;
-
-import android.annotation.TargetApi;
-import android.graphics.Rect;
-import android.os.Build;
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import android.transition.Transition;
-import android.transition.TransitionSet;
-import android.view.View;
-import android.view.ViewGroup;
-
-import java.util.List;
-import java.util.Map;
-
-@TargetApi(Build.VERSION_CODES.LOLLIPOP)
-public class TransitionUtils {
-
-    public static void findNamedViews(@NonNull Map<String, View> namedViews, View view) {
-        if (view.getVisibility() == View.VISIBLE) {
-            String transitionName = view.getTransitionName();
-            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(view.getTransitionName())) {
-            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 (!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/viewpager/src/main/java/com/bluelinelabs/conductor/viewpager/RouterPagerAdapter.java

@@ -6,6 +6,10 @@ 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;
@@ -15,12 +19,8 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
-import androidx.viewpager.widget.PagerAdapter;
-
 /**
- * An adapter for ViewPagers that uses Routers as pages
+ * An ViewPager adapter that uses Routers as pages
  */
 public abstract class RouterPagerAdapter extends PagerAdapter {
 

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

@@ -1,35 +1,42 @@
 package com.bluelinelabs.conductor.viewpager
 
 import android.app.Activity
+import android.os.Looper.getMainLooper
+import android.view.ViewGroup
 import android.widget.FrameLayout
 import androidx.core.view.ViewCompat
+import androidx.viewpager.widget.ViewPager
 import com.bluelinelabs.conductor.Conductor
 import com.bluelinelabs.conductor.Router
 import com.bluelinelabs.conductor.RouterTransaction.Companion.with
-import com.bluelinelabs.conductor.viewpager.util.FakePager
 import com.bluelinelabs.conductor.viewpager.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: FakePager
+  private val pager: ViewPager
   private val pagerAdapter: RouterPagerAdapter
+  private val destroyedItems = mutableListOf<Int>()
 
   init {
     val activityController = Robolectric.buildActivity(Activity::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 = FakePager(FrameLayout(activityController.get()).also {
+    pager = ViewPager(activityController.get()).also {
       it.id = ViewCompat.generateViewId()
-    })
+    }
+    layout.addView(pager)
     pager.offscreenPageLimit = 1
     pagerAdapter = object : RouterPagerAdapter(controller) {
       override fun configureRouter(router: Router, position: Int) {
@@ -41,21 +48,27 @@ class StateSaveTests {
       override fun getCount(): Int {
         return 20
       }
+
+      override fun destroyItem(container: ViewGroup, position: Int, `object`: Any) {
+        super.destroyItem(container, position, `object`)
+        destroyedItems.add(position)
+      }
     }
-    pager.setAdapter(pagerAdapter)
+    pager.adapter = pagerAdapter
+    shadowOf(getMainLooper()).idle()
   }
 
   @Test
   fun testNoMaxSaves() {
     // Load all pages
     for (i in 0 until pagerAdapter.count) {
-      pager.pageTo(i)
+      pager.currentItem = i
+      shadowOf(getMainLooper()).idle()
     }
-    pager.pageTo(pagerAdapter.count / 2)
 
     // Ensure all non-visible pages are saved
     assertEquals(
-      pagerAdapter.count - 1 - (pager.offscreenPageLimit * 2),
+      destroyedItems.size,
       pagerAdapter.savedPages.size()
     )
   }
@@ -67,38 +80,40 @@ class StateSaveTests {
 
     // Load all pages
     for (i in 0 until pagerAdapter.count) {
-      pager.pageTo(i)
+      pager.currentItem = i
+      shadowOf(getMainLooper()).idle()
     }
+
     val firstSelectedItem = pagerAdapter.count / 2
-    pager.pageTo(firstSelectedItem)
+    for (i in pagerAdapter.count downTo firstSelectedItem) {
+      pager.currentItem = i
+      shadowOf(getMainLooper()).idle()
+    }
+
     var savedPages = pagerAdapter.savedPages
 
     // Ensure correct number of pages are saved
     assertEquals(maxPages, savedPages.size())
 
     // Ensure correct pages are saved
-    assertEquals(
-      pagerAdapter.count - 3,
-      savedPages.keyAt(0)
-    )
-    assertEquals(
-      pagerAdapter.count - 2,
-      savedPages.keyAt(1)
-    )
-    assertEquals(
-      pagerAdapter.count - 1,
-      savedPages.keyAt(2)
-    )
+    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
-    pager.pageTo(secondSelectedItem)
+    for (i in firstSelectedItem downTo secondSelectedItem) {
+      pager.currentItem = i
+      shadowOf(getMainLooper()).idle()
+    }
+
     savedPages = pagerAdapter.savedPages
 
     // 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))
+    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/FakePager.java

@@ -1,61 +0,0 @@
-package com.bluelinelabs.conductor.viewpager.util;
-
-import android.util.SparseArray;
-import android.view.ViewGroup;
-
-import com.bluelinelabs.conductor.viewpager.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/viewpager2/build.gradle

@@ -1,4 +1,6 @@
 apply plugin: 'com.android.library'
+apply plugin: 'kotlin-android'
+apply plugin: 'kotlin-android-extensions'
 
 android {
     compileSdkVersion rootProject.ext.compileSdkVersion
@@ -9,13 +11,24 @@ android {
         versionCode Integer.parseInt(project.VERSION_CODE)
         versionName project.VERSION_NAME
     }
+
+    testOptions {
+        unitTests {
+            includeAndroidResources = true
+        }
+    }
 }
 
 dependencies {
+    testImplementation rootProject.ext.junit
+    testImplementation rootProject.ext.roboelectric
+
+    implementation rootProject.ext.androidxAppCompat
+    implementation rootProject.ext.androidxViewPager2
     implementation project(':conductor')
 }
 
-ext.artifactId = 'conductor-android-transition'
+ext.artifactId = 'conductor-viewpager2'
 
 apply from: rootProject.file('dependencies.gradle')
 apply plugin: "com.vanniktech.maven.publish"

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/AndroidManifest.xml

@@ -0,0 +1,3 @@
+<manifest package="com.bluelinelabs.conductor.viewpager2">
+    <application />
+</manifest>

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

@@ -0,0 +1,227 @@
+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.android.parcel.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)
+  }
+
+  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 {
+    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")
+    holder.currentRouter = router
+    holder.currentItemId = itemId
+
+    if (!router.hasRootController()) {
+      val routerSavedState = savedPages[position.toLong()]
+      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()
+
+      val savedState = Bundle()
+      router.saveInstanceState(savedState)
+      savedPages.put(holder.currentItemId, savedState)
+
+      savedPageHistory.remove(holder.currentItemId)
+      savedPageHistory.add(holder.currentItemId)
+
+      ensurePagesSaved()
+
+      if (visibleRouters[holder.currentItemPosition] == router) {
+        visibleRouters.remove(holder.currentItemPosition)
+      }
+    }
+
+    holder.attached = false
+  }
+
+  private fun ensurePagesSaved() {
+    while (savedPages.size() > maxPagesToStateSave) {
+      val positionToRemove = savedPageHistory.removeAt(0)
+      savedPages.remove(positionToRemove)
+    }
+  }
+
+  /**
+   * 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.app.Activity
+import android.os.Looper.getMainLooper
+import android.widget.FrameLayout
+import androidx.core.view.ViewCompat
+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(Activity::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

@@ -0,0 +1,21 @@
+package com.bluelinelabs.conductor.viewpager2.util;
+
+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 {
+
+    @Override @NonNull
+    protected View onCreateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container, @Nullable Bundle savedViewState) {
+        return new FrameLayout(inflater.getContext());
+    }
+
+}

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

@@ -5,9 +5,10 @@ import android.content.Intent;
 import android.content.IntentSender;
 import android.content.IntentSender.SendIntentException;
 import android.os.Bundle;
+import android.view.ViewGroup;
+
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
-import android.view.ViewGroup;
 
 import com.bluelinelabs.conductor.ControllerChangeHandler.ControllerChangeListener;
 import com.bluelinelabs.conductor.internal.LifecycleHandler;
@@ -57,9 +58,12 @@ 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

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

@@ -32,6 +32,7 @@ import java.lang.reflect.Constructor;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 import java.util.UUID;
 
@@ -228,7 +229,7 @@ public abstract class Controller {
         if (childRouter == null) {
             if (createIfNeeded) {
                 childRouter = new ControllerHostedRouter(container.getId(), tag);
-                childRouter.setHost(this, container);
+                childRouter.setHostContainer(this, container);
                 childRouters.add(childRouter);
 
                 if (isPerformingExitTransition) {
@@ -236,7 +237,7 @@ public abstract class Controller {
                 }
             }
         } else if (!childRouter.hasHost()) {
-            childRouter.setHost(this, container);
+            childRouter.setHostContainer(this, container);
             childRouter.rebindIfNeeded();
         }
 
@@ -522,21 +523,36 @@ public abstract class Controller {
      * Calls startActivity(Intent) from this Controller's host Activity.
      */
     public final void startActivity(@NonNull final Intent intent) {
-        executeWithRouter(() -> router.startActivity(intent));
+        executeWithRouter(new RouterRequiringFunc() {
+            @Override
+            public void execute() {
+                router.startActivity(intent);
+            }
+        });
     }
 
     /**
      * Calls startActivityForResult(Intent, int) from this Controller's host Activity.
      */
     public final void startActivityForResult(@NonNull final Intent intent, final int requestCode) {
-        executeWithRouter(() -> router.startActivityForResult(instanceId, intent, requestCode));
+        executeWithRouter(new RouterRequiringFunc() {
+            @Override
+            public void execute() {
+                router.startActivityForResult(instanceId, intent, requestCode);
+            }
+        });
     }
 
     /**
      * Calls startActivityForResult(Intent, int, Bundle) from this Controller's host Activity.
      */
     public final void startActivityForResult(@NonNull final Intent intent, final int requestCode, @Nullable final Bundle options) {
-        executeWithRouter(() -> router.startActivityForResult(instanceId, intent, requestCode, options));
+        executeWithRouter(new RouterRequiringFunc() {
+            @Override
+            public void execute() {
+                router.startActivityForResult(instanceId, intent, requestCode, options);
+            }
+        });
     }
 
     /**
@@ -554,7 +570,12 @@ public abstract class Controller {
      * @param requestCode The request code being registered for.
      */
     public final void registerForActivityResult(final int requestCode) {
-        executeWithRouter(() -> router.registerForActivityResult(instanceId, requestCode));
+        executeWithRouter(new RouterRequiringFunc() {
+            @Override
+            public void execute() {
+                router.registerForActivityResult(instanceId, requestCode);
+            }
+        });
     }
 
     /**
@@ -577,7 +598,12 @@ public abstract class Controller {
     public final void requestPermissions(@NonNull final String[] permissions, final int requestCode) {
         requestedPermissions.addAll(Arrays.asList(permissions));
 
-        executeWithRouter(() -> router.requestPermissions(instanceId, permissions, requestCode));
+        executeWithRouter(new RouterRequiringFunc() {
+            @Override
+            public void execute() {
+                router.requestPermissions(instanceId, permissions, requestCode);
+            }
+        });
     }
 
     /**
@@ -612,7 +638,12 @@ public abstract class Controller {
             childTransactions.addAll(childRouter.getBackstack());
         }
 
-        Collections.sort(childTransactions, (o1, o2) -> o2.getTransactionIndex() - o1.getTransactionIndex());
+        Collections.sort(childTransactions, new Comparator<RouterTransaction>() {
+            @Override
+            public int compare(RouterTransaction o1, RouterTransaction o2) {
+                return o2.getTransactionIndex() - o1.getTransactionIndex();
+            }
+        });
 
         for (RouterTransaction transaction : childTransactions) {
             Controller childController = transaction.controller();
@@ -987,7 +1018,11 @@ public abstract class Controller {
 
             onDestroyView(view);
 
-            viewAttachHandler.unregisterAttachListener(view);
+            // viewAttachHandler may be null iff the controller was popped before we got here
+            if (viewAttachHandler != null) {
+                viewAttachHandler.unregisterAttachListener(view);
+            }
+
             viewAttachHandler = null;
             viewIsAttached = false;
 
@@ -1036,32 +1071,34 @@ public abstract class Controller {
 
             restoreViewState(view);
 
-            viewAttachHandler = new ViewAttachHandler(new ViewAttachListener() {
-                @Override
-                public void onAttached() {
-                    viewIsAttached = true;
-                    viewWasDetached = false;
-                    attach(view);
-                }
-
-                @Override
-                public void onDetached(boolean fromActivityStop) {
-                    viewIsAttached = false;
-                    viewWasDetached = true;
-
-                    if (!isDetachFrozen) {
-                        detach(view, false, fromActivityStop);
+            if (!isBeingDestroyed) {
+                viewAttachHandler = new ViewAttachHandler(new ViewAttachListener() {
+                    @Override
+                    public void onAttached() {
+                        viewIsAttached = true;
+                        viewWasDetached = false;
+                        attach(view);
                     }
-                }
 
-                @Override
-                public void onViewDetachAfterStop() {
-                    if (!isDetachFrozen) {
-                        detach(view, false, false);
+                    @Override
+                    public void onDetached(boolean fromActivityStop) {
+                        viewIsAttached = false;
+                        viewWasDetached = true;
+
+                        if (!isDetachFrozen) {
+                            detach(view, false, fromActivityStop);
+                        }
                     }
-                }
-            });
-            viewAttachHandler.listenForAttach(view);
+
+                    @Override
+                    public void onViewDetachAfterStop() {
+                        if (!isDetachFrozen) {
+                            detach(view, false, false);
+                        }
+                    }
+                });
+                viewAttachHandler.listenForAttach(view);
+            }
         } else if (retainViewMode == RetainViewMode.RETAIN_DETACH) {
             restoreChildControllerHosts();
         }
@@ -1075,7 +1112,7 @@ public abstract class Controller {
                 View containerView = view.findViewById(childRouter.getHostId());
 
                 if (containerView != null && containerView instanceof ViewGroup) {
-                    childRouter.setHost(this, (ViewGroup) containerView);
+                    childRouter.setHostContainer(this, (ViewGroup) containerView);
                     childRouter.rebindIfNeeded();
                 }
             }
@@ -1234,6 +1271,7 @@ public abstract class Controller {
         List<Bundle> childBundles = savedInstanceState.getParcelableArrayList(KEY_CHILD_ROUTERS);
         for (Bundle childBundle : childBundles) {
             ControllerHostedRouter childRouter = new ControllerHostedRouter();
+            childRouter.setHostController(this);
             childRouter.restoreInstanceState(childBundle);
             childRouters.add(childRouter);
         }
@@ -1382,66 +1420,66 @@ public abstract class Controller {
     /**
      * Allows external classes to listen for lifecycle events in a Controller
      */
-    public interface LifecycleListener {
+    public static abstract class LifecycleListener {
 
-        default void onChangeStart(@NonNull Controller controller, @NonNull ControllerChangeHandler changeHandler, @NonNull ControllerChangeType changeType) {
+        public void onChangeStart(@NonNull Controller controller, @NonNull ControllerChangeHandler changeHandler, @NonNull ControllerChangeType changeType) {
         }
 
-        default void onChangeEnd(@NonNull Controller controller, @NonNull ControllerChangeHandler changeHandler, @NonNull ControllerChangeType changeType) {
+        public void onChangeEnd(@NonNull Controller controller, @NonNull ControllerChangeHandler changeHandler, @NonNull ControllerChangeType changeType) {
         }
 
-        default void preCreateView(@NonNull Controller controller) {
+        public void preCreateView(@NonNull Controller controller) {
         }
 
-        default void postCreateView(@NonNull Controller controller, @NonNull View view) {
+        public void postCreateView(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void preAttach(@NonNull Controller controller, @NonNull View view) {
+        public void preAttach(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void postAttach(@NonNull Controller controller, @NonNull View view) {
+        public void postAttach(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void preDetach(@NonNull Controller controller, @NonNull View view) {
+        public void preDetach(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void postDetach(@NonNull Controller controller, @NonNull View view) {
+        public void postDetach(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void preDestroyView(@NonNull Controller controller, @NonNull View view) {
+        public void preDestroyView(@NonNull Controller controller, @NonNull View view) {
         }
 
-        default void postDestroyView(@NonNull Controller controller) {
+        public void postDestroyView(@NonNull Controller controller) {
         }
 
-        default void preDestroy(@NonNull Controller controller) {
+        public void preDestroy(@NonNull Controller controller) {
         }
 
-        default void postDestroy(@NonNull Controller controller) {
+        public void postDestroy(@NonNull Controller controller) {
         }
 
-        default void preContextAvailable(@NonNull Controller controller) {
+        public void preContextAvailable(@NonNull Controller controller) {
         }
 
-        default void postContextAvailable(@NonNull Controller controller, @NonNull Context context) {
+        public void postContextAvailable(@NonNull Controller controller, @NonNull Context context) {
         }
 
-        default void preContextUnavailable(@NonNull Controller controller, @NonNull Context context) {
+        public void preContextUnavailable(@NonNull Controller controller, @NonNull Context context) {
         }
 
-        default void postContextUnavailable(@NonNull Controller controller) {
+        public void postContextUnavailable(@NonNull Controller controller) {
         }
 
-        default void onSaveInstanceState(@NonNull Controller controller, @NonNull Bundle outState) {
+        public void onSaveInstanceState(@NonNull Controller controller, @NonNull Bundle outState) {
         }
 
-        default void onRestoreInstanceState(@NonNull Controller controller, @NonNull Bundle savedInstanceState) {
+        public void onRestoreInstanceState(@NonNull Controller controller, @NonNull Bundle savedInstanceState) {
         }
 
-        default void onSaveViewState(@NonNull Controller controller, @NonNull Bundle outState) {
+        public void onSaveViewState(@NonNull Controller controller, @NonNull Bundle outState) {
         }
 
-        default void onRestoreViewState(@NonNull Controller controller, @NonNull Bundle savedViewState) {
+        public void onRestoreViewState(@NonNull Controller controller, @NonNull Bundle savedViewState) {
         }
 
     }

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

@@ -206,29 +206,32 @@ public abstract class ControllerChangeHandler {
                 fromView = null;
             }
 
-            handler.performChange(container, fromView, toView, isPush, () -> {
-                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);
+            handler.performChange(container, fromView, toView, isPush, new ControllerChangeCompletedListener() {
+                @Override
+                public void onChangeCompleted() {
+                    if (from != null) {
+                        from.changeEnded(handler, fromChangeType);
                     }
-                }
 
-                if (handler.removesFromViewOnPush() && from != null) {
-                    from.setNeedsAttach(false);
+                    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);
+                    }
                 }
             });
         }
@@ -258,8 +261,7 @@ public abstract class ControllerChangeHandler {
          * @param container The containing ViewGroup
          * @param handler   The change handler being used.
          */
-        default void onChangeStarted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler) {
-        }
+        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
@@ -270,8 +272,7 @@ public abstract class ControllerChangeHandler {
          * @param container The containing ViewGroup
          * @param handler   The change handler that was used.
          */
-        default void onChangeCompleted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler) {
-        }
+        void onChangeCompleted(@Nullable Controller to, @Nullable Controller from, boolean isPush, @NonNull ViewGroup container, @NonNull ControllerChangeHandler handler);
     }
 
     static class ChangeTransaction {

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

@@ -36,12 +36,18 @@ class ControllerHostedRouter extends Router {
         this.tag = tag;
     }
 
-    final void setHost(@NonNull Controller controller, @NonNull ViewGroup container) {
+    final void setHostController(@NonNull Controller controller) {
+        if (hostController == null) {
+            hostController = controller;
+        }
+    }
+
+    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;
@@ -57,7 +63,7 @@ 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);
@@ -73,7 +79,6 @@ class ControllerHostedRouter extends Router {
         }
 
         prepareForContainerRemoval();
-        hostController = null;
         container = null;
     }
 
@@ -108,14 +113,29 @@ class ControllerHostedRouter extends Router {
         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().removesFromViewOnPush()) {
+                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();
     }
@@ -185,7 +205,7 @@ class ControllerHostedRouter extends Router {
 
     @Override
     boolean hasHost() {
-        return hostController != null;
+        return hostController != null && container != null;
     }
 
     @Override
@@ -205,9 +225,9 @@ class ControllerHostedRouter extends Router {
     }
 
     @Override
-    void setControllerRouter(@NonNull Controller controller) {
+    void setRouterOnController(@NonNull Controller controller) {
         controller.setParentController(hostController);
-        super.setControllerRouter(controller);
+        super.setRouterOnController(controller);
     }
 
     int getHostId() {

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

@@ -205,7 +205,7 @@ public abstract class Router {
             final boolean oldHandlerRemovedViews = topTransaction.pushChangeHandler() == null || topTransaction.pushChangeHandler().removesFromViewOnPush();
             final boolean newHandlerRemovesViews = handler == null || handler.removesFromViewOnPush();
             if (!oldHandlerRemovedViews && newHandlerRemovesViews) {
-                for (RouterTransaction visibleTransaction : getVisibleTransactions(backstack.iterator())) {
+                for (RouterTransaction visibleTransaction : getVisibleTransactions(backstack.iterator(), true)) {
                     performControllerChange(null, visibleTransaction, true, handler);
                 }
             }
@@ -404,7 +404,7 @@ public abstract class Router {
         ThreadUtils.ensureMainThread();
 
         List<RouterTransaction> oldTransactions = getBackstack();
-        List<RouterTransaction> oldVisibleTransactions = getVisibleTransactions(backstack.iterator());
+        List<RouterTransaction> oldVisibleTransactions = getVisibleTransactions(backstack.iterator(), false);
 
         removeAllExceptVisibleAndUnowned();
         ensureOrderedTransactionIndices(newBackstack);
@@ -434,13 +434,13 @@ public abstract class Router {
         while (backstackIterator.hasNext()) {
             RouterTransaction transaction = backstackIterator.next();
             transaction.onAttachedToRouter();
-            setControllerRouter(transaction.controller());
+            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);
@@ -464,7 +464,10 @@ public abstract class Router {
                         ControllerChangeHandler localHandler = changeHandler != null ? changeHandler.copy() : new SimpleSwapChangeHandler();
                         localHandler.setForceRemoveViewOnPush(true);
                         ControllerChangeHandler.completeHandlerImmediately(transaction.controller().getInstanceId());
-                        performControllerChange(null, transaction, newRootRequiresPush, localHandler);
+
+                        if (transaction.controller().view != null) {
+                            performControllerChange(null, transaction, newRootRequiresPush, localHandler);
+                        }
                     }
                 }
 
@@ -549,7 +552,7 @@ public abstract class Router {
             if (transaction.controller().getNeedsAttach()) {
                 performControllerChange(transaction, null, true, new SimpleSwapChangeHandler(false));
             } else {
-                setControllerRouter(transaction.controller());
+                setRouterOnController(transaction.controller());
             }
         }
     }
@@ -605,7 +608,7 @@ public abstract class Router {
         isActivityStopped = true;
     }
 
-    public void onActivityDestroyed(@NonNull Activity activity) {
+    public void onActivityDestroyed(@NonNull Activity activity, boolean isConfigurationChange) {
         prepareForContainerRemoval();
         changeListeners.clear();
 
@@ -613,7 +616,7 @@ public abstract class Router {
             transaction.controller().activityDestroyed(activity);
 
             for (Router childRouter : transaction.controller().getChildRouters()) {
-                childRouter.onActivityDestroyed(activity);
+                childRouter.onActivityDestroyed(activity, isConfigurationChange);
             }
         }
 
@@ -622,7 +625,7 @@ public abstract class Router {
             controller.activityDestroyed(activity);
 
             for (Router childRouter : controller.getChildRouters()) {
-                childRouter.onActivityDestroyed(activity);
+                childRouter.onActivityDestroyed(activity, isConfigurationChange);
             }
         }
 
@@ -657,7 +660,7 @@ public abstract class Router {
 
         Iterator<RouterTransaction> backstackIterator = backstack.reverseIterator();
         while (backstackIterator.hasNext()) {
-            setControllerRouter(backstackIterator.next().controller());
+            setRouterOnController(backstackIterator.next().controller());
         }
     }
 
@@ -720,7 +723,12 @@ public abstract class Router {
     }
 
     void watchContainerAttach() {
-        container.post(() -> containerFullyAttached = true);
+        container.post(new Runnable() {
+            @Override
+            public void run() {
+                containerFullyAttached = true;
+            }
+        });
     }
 
     void prepareForContainerRemoval() {
@@ -759,7 +767,7 @@ public abstract class Router {
         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();
         }
@@ -784,7 +792,7 @@ public abstract class Router {
 
         if (to != null) {
             to.ensureValidIndex(getTransactionIndexer());
-            setControllerRouter(toController);
+            setRouterOnController(toController);
         } else if (backstack.size() == 0 && !popsLastView) {
             // 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.
@@ -802,7 +810,7 @@ public abstract class Router {
             if (fromController.getView() != null) {
                 fromController.detach(fromController.getView(), true, false);
             } else {
-                from.controller().destroy();
+                fromController.destroy();
             }
         }
     }
@@ -829,7 +837,12 @@ public abstract class Router {
                 to.setNeedsAttach(true);
             }
             pendingControllerChanges.add(transaction);
-            container.post(this::performPendingControllerChanges);
+            container.post(new Runnable() {
+                @Override
+                public void run() {
+                    performPendingControllerChanges();
+                }
+            });
         } else {
             ControllerChangeHandler.executeChange(transaction);
         }
@@ -873,7 +886,7 @@ public abstract class Router {
     private void removeAllExceptVisibleAndUnowned() {
         List<View> views = new ArrayList<>();
 
-        for (RouterTransaction transaction : getVisibleTransactions(backstack.iterator())) {
+        for (RouterTransaction transaction : getVisibleTransactions(backstack.iterator(), false)) {
             if (transaction.controller().getView() != null) {
                 views.add(transaction.controller().getView());
             }
@@ -933,14 +946,20 @@ 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().removesFromViewOnPush();
+
+            if (onlyTop && !visible) {
                 break;
             }
         }
@@ -963,7 +982,7 @@ public abstract class Router {
         return true;
     }
 
-    void setControllerRouter(@NonNull Controller controller) {
+    void setRouterOnController(@NonNull Controller controller) {
         controller.setRouter(this);
         controller.onContextAvailable();
     }

conductor/src/main/java/com/bluelinelabs/conductor/internal/LifecycleHandler.java

@@ -101,7 +101,7 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
 
     @NonNull
     public List<Router> getRouters() {
-        return new ArrayList<>(routerMap.values());
+        return new ArrayList<Router>(routerMap.values());
     }
 
     @Nullable
@@ -133,13 +133,13 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
 
         if (savedInstanceState != null) {
             StringSparseArrayParceler permissionParcel = savedInstanceState.getParcelable(KEY_PERMISSION_REQUEST_CODES);
-            permissionRequestMap = permissionParcel != null ? permissionParcel.getStringSparseArray() : new SparseArray<>();
+            permissionRequestMap = permissionParcel != null ? permissionParcel.getStringSparseArray() : new SparseArray<String>();
 
             StringSparseArrayParceler activityParcel = savedInstanceState.getParcelable(KEY_ACTIVITY_REQUEST_CODES);
-            activityRequestMap = activityParcel != null ? activityParcel.getStringSparseArray() : new SparseArray<>();
+            activityRequestMap = activityParcel != null ? activityParcel.getStringSparseArray() : new SparseArray<String>();
 
             ArrayList<PendingPermissionRequest> pendingRequests = savedInstanceState.getParcelableArrayList(KEY_PENDING_PERMISSION_REQUESTS);
-            pendingPermissionRequests = pendingRequests != null ? pendingRequests : new ArrayList<>();
+            pendingPermissionRequests = pendingRequests != null ? pendingRequests : new ArrayList<PendingPermissionRequest>();
         }
     }
 
@@ -159,13 +159,16 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
         if (activity != null) {
             activity.getApplication().unregisterActivityLifecycleCallbacks(this);
             activeLifecycleHandlers.remove(activity);
-            destroyRouters();
+            destroyRouters(false);
             activity = null;
         }
+
+        routerMap.clear();
     }
 
     @Override
     public void onAttach(Activity activity) {
+        this.activity = activity;
         super.onAttach(activity);
         destroyed = false;
         setAttached();
@@ -173,6 +176,10 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
 
     @Override
     public void onAttach(Context context) {
+        if (context instanceof Activity) {
+            this.activity = (Activity) context;
+        }
+
         super.onAttach(context);
         destroyed = false;
         setAttached();
@@ -183,7 +190,10 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
         super.onDetach();
 
         attached = false;
-        destroyRouters();
+
+        if (activity != null) {
+            destroyRouters(activity.isChangingConfigurations());
+        }
     }
 
     private void setAttached() {
@@ -194,20 +204,20 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
                 PendingPermissionRequest request = pendingPermissionRequests.remove(i);
                 requestPermissions(request.instanceId, request.permissions, request.requestCode);
             }
-        }
 
-        for (ActivityHostedRouter router : new ArrayList<>(routerMap.values())) {
-            router.onContextAvailable();
+            for (ActivityHostedRouter router : new ArrayList<>(routerMap.values())) {
+                router.onContextAvailable();
+            }
         }
     }
 
-    private void destroyRouters() {
+    private void destroyRouters(boolean configurationChange) {
         if (!destroyed) {
             destroyed = true;
 
             if (activity != null) {
                 for (Router router : getRouters()) {
-                    router.onActivityDestroyed(activity);
+                    router.onActivityDestroyed(activity, configurationChange);
                 }
             }
         }
@@ -319,7 +329,7 @@ public class LifecycleHandler extends Fragment implements ActivityLifecycleCallb
 
     @Override
     public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
-        if (this.activity == null && findInActivity(activity) == LifecycleHandler.this) {
+        if (findInActivity(activity) == LifecycleHandler.this) {
             this.activity = activity;
 
             for (ActivityHostedRouter router : new ArrayList<>(routerMap.values())) {

conductor/src/main/java/com/bluelinelabs/conductor/internal/ViewAttachHandler.java

@@ -40,10 +40,12 @@ public class ViewAttachHandler implements OnAttachStateChangeListener {
         }
 
         rootAttached = true;
-        listenForDeepestChildAttach(v, () -> {
-            childrenAttached = true;
-            reportAttached();
-
+        listenForDeepestChildAttach(v, new ChildAttachListener() {
+            @Override
+            public void onAttached() {
+                childrenAttached = true;
+                reportAttached();
+            }
         });
     }
 
@@ -65,6 +67,7 @@ public class ViewAttachHandler implements OnAttachStateChangeListener {
 
         if (childOnAttachStateChangeListener != null && view instanceof ViewGroup) {
             findDeepestChild((ViewGroup)view).removeOnAttachStateChangeListener(childOnAttachStateChangeListener);
+            childOnAttachStateChangeListener = null;
         }
     }
 
@@ -118,7 +121,7 @@ public class ViewAttachHandler implements OnAttachStateChangeListener {
 
             @Override
             public void onViewAttachedToWindow(View v) {
-                if (!attached) {
+                if (!attached && childOnAttachStateChangeListener != null) {
                     attached = true;
                     attachListener.onAttached();
                     v.removeOnAttachStateChangeListener(this);

conductor/src/test/java/com/bluelinelabs/conductor/ControllerLifecycleActivityReferenceTests.java

@@ -2,6 +2,7 @@ package com.bluelinelabs.conductor;
 
 import android.os.Bundle;
 import android.view.View;
+import android.view.ViewGroup;
 
 import androidx.annotation.NonNull;
 
@@ -85,7 +86,7 @@ public class ControllerLifecycleActivityReferenceTests {
         ActivityReferencingLifecycleListener listener = new ActivityReferencingLifecycleListener();
         child.addLifecycleListener(listener);
 
-        Router childRouter = parent.getChildRouter(parent.getView().findViewById(TestController.VIEW_ID));
+        Router childRouter = parent.getChildRouter((ViewGroup) parent.getView().findViewById(TestController.VIEW_ID));
         childRouter.pushController(RouterTransaction.with(child)
                 .pushChangeHandler(MockChangeHandler.defaultHandler())
                 .popChangeHandler(MockChangeHandler.defaultHandler()));
@@ -132,7 +133,7 @@ public class ControllerLifecycleActivityReferenceTests {
         ActivityReferencingLifecycleListener listener = new ActivityReferencingLifecycleListener();
         child.addLifecycleListener(listener);
 
-        Router childRouter = parent.getChildRouter(parent.getView().findViewById(TestController.VIEW_ID));
+        Router childRouter = parent.getChildRouter((ViewGroup) parent.getView().findViewById(TestController.VIEW_ID));
         childRouter.setPopsLastView(true);
         childRouter.pushController(RouterTransaction.with(child)
                 .pushChangeHandler(MockChangeHandler.defaultHandler())
@@ -161,7 +162,7 @@ public class ControllerLifecycleActivityReferenceTests {
         ActivityReferencingLifecycleListener listener = new ActivityReferencingLifecycleListener();
         child.addLifecycleListener(listener);
 
-        Router childRouter = parent.getChildRouter(parent.getView().findViewById(TestController.VIEW_ID));
+        Router childRouter = parent.getChildRouter((ViewGroup) parent.getView().findViewById(TestController.VIEW_ID));
         childRouter.setPopsLastView(true);
         childRouter.pushController(RouterTransaction.with(child)
                 .pushChangeHandler(MockChangeHandler.defaultHandler())
@@ -211,7 +212,7 @@ public class ControllerLifecycleActivityReferenceTests {
         ActivityReferencingLifecycleListener listener = new ActivityReferencingLifecycleListener();
         child.addLifecycleListener(listener);
 
-        Router childRouter = parent.getChildRouter(parent.getView().findViewById(TestController.VIEW_ID));
+        Router childRouter = parent.getChildRouter((ViewGroup) parent.getView().findViewById(TestController.VIEW_ID));
         childRouter.setPopsLastView(true);
         childRouter.pushController(RouterTransaction.with(child)
                 .pushChangeHandler(MockChangeHandler.defaultHandler())
@@ -227,7 +228,7 @@ public class ControllerLifecycleActivityReferenceTests {
         assertEquals(Collections.singletonList(true), listener.postDestroyReferences);
     }
 
-    static class ActivityReferencingLifecycleListener implements Controller.LifecycleListener {
+    static class ActivityReferencingLifecycleListener extends Controller.LifecycleListener {
         final List<Boolean> changeEndReferences = new ArrayList<>();
         final List<Boolean> postCreateViewReferences = new ArrayList<>();
         final List<Boolean> postAttachReferences = new ArrayList<>();

conductor/src/test/java/com/bluelinelabs/conductor/ControllerLifecycleCallbacksTests.java

@@ -2,10 +2,11 @@ package com.bluelinelabs.conductor;
 
 import android.content.Context;
 import android.os.Bundle;
-import androidx.annotation.NonNull;
 import android.view.View;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+
 import com.bluelinelabs.conductor.Controller.LifecycleListener;
 import com.bluelinelabs.conductor.Controller.RetainViewMode;
 import com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler;
@@ -590,6 +591,34 @@ public class ControllerLifecycleCallbacksTests {
         assertTrue(child.isAttached());
     }
 
+    @Test
+    public void testChildLifecycleAfterPushPopPush() {
+        Controller parent = new TestController();
+        parent.setRetainViewMode(RetainViewMode.RETAIN_DETACH);
+        router.pushController(RouterTransaction.with(parent)
+                .pushChangeHandler(MockChangeHandler.defaultHandler())
+                .popChangeHandler(MockChangeHandler.defaultHandler()));
+
+        TestController child = new TestController();
+        Router childRouter = parent.getChildRouter((ViewGroup)parent.getView().findViewById(TestController.VIEW_ID));
+        childRouter
+                .setRoot(RouterTransaction.with(child)
+                        .pushChangeHandler(new SimpleSwapChangeHandler())
+                        .popChangeHandler(new SimpleSwapChangeHandler()));
+
+        Controller nextController = new TestController();
+        router.pushController(RouterTransaction.with(nextController));
+
+        TestController child2 = new TestController();
+        childRouter.pushController(RouterTransaction.with(child2));
+
+        router.popCurrentController();
+
+        assertTrue(parent.isAttached());
+        assertFalse(child.isAttached());
+        assertTrue(child2.isAttached());
+    }
+
     private MockChangeHandler getPushHandler(final CallState expectedCallState, final TestController controller) {
         return MockChangeHandler.listeningChangeHandler(new ChangeHandlerListener() {
             @Override

conductor/src/test/java/com/bluelinelabs/conductor/ReattachCaseTests.java

@@ -8,7 +8,6 @@ import com.bluelinelabs.conductor.util.ActivityProxy;
 import com.bluelinelabs.conductor.util.AttachFakingFrameLayout;
 import com.bluelinelabs.conductor.util.MockChangeHandler;
 import com.bluelinelabs.conductor.util.TestController;
-import com.bluelinelabs.conductor.util.ViewUtils;
 
 import org.junit.Before;
 import org.junit.Test;
@@ -17,6 +16,7 @@ import org.robolectric.RobolectricTestRunner;
 import org.robolectric.annotation.Config;
 
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
 
 @RunWith(RobolectricTestRunner.class)
@@ -80,7 +80,7 @@ public class ReattachCaseTests {
                 .pushChangeHandler(MockChangeHandler.defaultHandler())
                 .popChangeHandler(MockChangeHandler.defaultHandler()));
 
-        Router childRouter = controllerA.getChildRouter((ViewGroup)controllerA.getView().findViewById(TestController.VIEW_ID));
+        Router childRouter = controllerA.getChildRouter((ViewGroup) controllerA.getView().findViewById(TestController.VIEW_ID));
         childRouter.pushController(RouterTransaction.with(childController)
             .pushChangeHandler(MockChangeHandler.defaultHandler())
             .popChangeHandler(MockChangeHandler.defaultHandler()));
@@ -350,6 +350,54 @@ public class ReattachCaseTests {
         assertTrue(controller2.isAttached());
     }
 
+    @Test
+    public void testHostAvailableDuringRotation() {
+        final Controller controllerA = new TestController();
+        final Controller childControllerA = new TestController();
+        final Controller controllerB = new TestController();
+        final Controller childControllerB = new TestController();
+
+        router.pushController(RouterTransaction.with(controllerA)
+                .pushChangeHandler(MockChangeHandler.defaultHandler())
+                .popChangeHandler(MockChangeHandler.defaultHandler()));
+
+        Router childRouterA = controllerA.getChildRouter((ViewGroup) controllerA.getView().findViewById(TestController.VIEW_ID));
+        childRouterA.pushController(RouterTransaction.with(childControllerA)
+                .pushChangeHandler(MockChangeHandler.defaultHandler())
+                .popChangeHandler(MockChangeHandler.defaultHandler()));
+
+        assertNotNull(controllerA.getActivity());
+        assertNotNull(childControllerA.getActivity());
+
+        router.pushController(RouterTransaction.with(controllerB)
+                .pushChangeHandler(MockChangeHandler.defaultHandler())
+                .popChangeHandler(MockChangeHandler.defaultHandler()));
+
+        Router childRouterB = controllerB.getChildRouter((ViewGroup) controllerB.getView().findViewById(TestController.VIEW_ID));
+        childRouterB.pushController(RouterTransaction.with(childControllerB)
+                .pushChangeHandler(MockChangeHandler.defaultHandler())
+                .popChangeHandler(MockChangeHandler.defaultHandler()));
+
+        assertNotNull(controllerA.getActivity());
+        assertNotNull(childControllerA.getActivity());
+        assertNotNull(controllerB.getActivity());
+        assertNotNull(childControllerB.getActivity());
+
+        activityProxy.rotate();
+
+        assertNotNull(controllerA.getActivity());
+        assertNotNull(childControllerA.getActivity());
+        assertNotNull(controllerB.getActivity());
+        assertNotNull(childControllerB.getActivity());
+
+        router.rebindIfNeeded();
+
+        assertNotNull(controllerA.getActivity());
+        assertNotNull(childControllerA.getActivity());
+        assertNotNull(controllerB.getActivity());
+        assertNotNull(childControllerB.getActivity());
+    }
+
     private void sleepWakeDevice() {
         activityProxy.saveInstanceState(new Bundle()).pause();
         activityProxy.resume();

conductor/src/test/java/com/bluelinelabs/conductor/ViewLeakTests.java

@@ -1,11 +1,13 @@
 package com.bluelinelabs.conductor;
 
 import android.os.Bundle;
-import androidx.annotation.NonNull;
-import androidx.annotation.Nullable;
 import android.view.View;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
+import com.bluelinelabs.conductor.changehandler.SimpleSwapChangeHandler;
 import com.bluelinelabs.conductor.util.ActivityProxy;
 import com.bluelinelabs.conductor.util.TestController;
 
@@ -110,6 +112,25 @@ public class ViewLeakTests {
         assertNull(controller.getView());
     }
 
+    @Test
+    public void testViewRemovedIfLayeredNotRemovesFromViewOnPush() {
+        Controller controller = new TestController();
+        router.pushController(RouterTransaction.with(controller));
+
+        router.pushController(RouterTransaction.with(new TestController()).pushChangeHandler(new SimpleSwapChangeHandler(false)));
+
+        View view = controller.view;
+        assertNotNull(view.getParent());
+
+        router.pushController(RouterTransaction.with(new TestController()));
+
+        assertNotNull(view.getParent());
+
+        router.popToRoot();
+
+        assertNull(view.getParent());
+    }
+
     public static class NeverAddChangeHandler extends ControllerChangeHandler {
         @Override
         public void performChange(@NonNull final ViewGroup container, @Nullable View from, @Nullable final View to, boolean isPush, @NonNull ControllerChangeCompletedListener changeListener) {

demo/build.gradle

@@ -4,8 +4,8 @@ android {
     compileSdkVersion rootProject.ext.compileSdkVersion
 
     compileOptions {
-        sourceCompatibility 1.8
-        targetCompatibility 1.8
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
     }
 
     defaultConfig {
@@ -31,6 +31,7 @@ android {
 
 dependencies {
     implementation rootProject.ext.androidxAppCompat
+    implementation rootProject.ext.androidxViewPager2
     implementation rootProject.ext.material
 
     implementation rootProject.ext.archComponentsLiveDataCore // Fix duplicate classes
@@ -41,10 +42,11 @@ dependencies {
 
     implementation project(':conductor')
     implementation project(':conductor-modules:viewpager')
+    implementation project(':conductor-modules:viewpager2')
     implementation project(':conductor-modules:rxlifecycle2')
     implementation project(':conductor-modules:autodispose')
     implementation project(':conductor-modules:arch-components-lifecycle')
-    implementation project(':conductor-modules:transition-androidx')
+    implementation project(':conductor-modules:androidx-transition')
 
     debugImplementation rootProject.ext.leakCanary
     releaseImplementation rootProject.ext.leakCanaryNoOp

demo/src/main/java/com/bluelinelabs/conductor/demo/changehandler/CircularRevealChangeHandler.java

@@ -51,7 +51,7 @@ public class CircularRevealChangeHandler extends AnimatorChangeHandler {
      * @param removesFromViewOnPush If true, the view being replaced will be removed from the view hierarchy on pushes
      */
     public CircularRevealChangeHandler(@NonNull View fromView, @NonNull View containerView, boolean removesFromViewOnPush) {
-        this(fromView, containerView, DEFAULT_ANIMATION_DURATION, true);
+        this(fromView, containerView, DEFAULT_ANIMATION_DURATION, removesFromViewOnPush);
     }
 
     /**

demo/src/main/java/com/bluelinelabs/conductor/demo/controllers/ChildController.java

@@ -1,13 +1,14 @@
 package com.bluelinelabs.conductor.demo.controllers;
 
 import android.os.Bundle;
-import androidx.annotation.NonNull;
-import androidx.core.content.ContextCompat;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.TextView;
 
+import androidx.annotation.NonNull;
+import androidx.core.content.ContextCompat;
+
 import com.bluelinelabs.conductor.demo.R;
 import com.bluelinelabs.conductor.demo.controllers.base.BaseController;
 import com.bluelinelabs.conductor.demo.util.BundleBuilder;

demo/src/main/java/com/bluelinelabs/conductor/demo/controllers/HomeController.java

@@ -48,11 +48,12 @@ public class HomeController extends BaseController {
         SHARED_ELEMENT_TRANSITIONS("Shared Element Demos", R.color.purple_300),
         CHILD_CONTROLLERS("Child Controllers", R.color.orange_300),
         VIEW_PAGER("ViewPager", R.color.green_300),
-        TARGET_CONTROLLER("Target Controller", R.color.pink_300),
-        MULTIPLE_CHILD_ROUTERS("Multiple Child Routers", R.color.deep_orange_300),
-        MASTER_DETAIL("Master Detail", R.color.grey_300),
-        DRAG_DISMISS("Drag Dismiss", R.color.lime_300),
-        EXTERNAL_MODULES("Bonus Modules", R.color.teal_300);
+        VIEW_PAGER_2("ViewPager2", R.color.pink_300),
+        TARGET_CONTROLLER("Target Controller", R.color.deep_orange_300),
+        MULTIPLE_CHILD_ROUTERS("Multiple Child Routers", R.color.grey_300),
+        MASTER_DETAIL("Master Detail", R.color.lime_300),
+        DRAG_DISMISS("Drag Dismiss", R.color.teal_300),
+        EXTERNAL_MODULES("Bonus Modules", R.color.deep_purple_300);
 
         String title;
         @ColorRes int color;
@@ -182,7 +183,12 @@ public class HomeController extends BaseController {
                                 .popChangeHandler(new FadeChangeHandler()));
                 break;
             case VIEW_PAGER:
-                getRouter().pushController(RouterTransaction.with(new PagerController())
+                getRouter().pushController(RouterTransaction.with(new ViewPagerController())
+                        .pushChangeHandler(new FadeChangeHandler())
+                        .popChangeHandler(new FadeChangeHandler()));
+                break;
+            case VIEW_PAGER_2:
+                getRouter().pushController(RouterTransaction.with(new ViewPager2Controller())
                         .pushChangeHandler(new FadeChangeHandler())
                         .popChangeHandler(new FadeChangeHandler()));
                 break;

demo/src/main/java/com/bluelinelabs/conductor/demo/controllers/ViewPager2Controller.java

@@ -0,0 +1,76 @@
+package com.bluelinelabs.conductor.demo.controllers;
+
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import androidx.annotation.NonNull;
+import androidx.viewpager2.widget.ViewPager2;
+
+import com.bluelinelabs.conductor.Controller;
+import com.bluelinelabs.conductor.Router;
+import com.bluelinelabs.conductor.RouterTransaction;
+import com.bluelinelabs.conductor.demo.R;
+import com.bluelinelabs.conductor.demo.controllers.base.BaseController;
+import com.bluelinelabs.conductor.viewpager2.RouterStateAdapter;
+import com.google.android.material.tabs.TabLayout;
+import com.google.android.material.tabs.TabLayoutMediator;
+
+import java.util.Locale;
+
+import butterknife.BindView;
+
+public class ViewPager2Controller extends BaseController {
+
+    private int[] PAGE_COLORS = new int[]{R.color.green_300, R.color.cyan_300, R.color.deep_purple_300, R.color.lime_300, R.color.red_300};
+
+    @BindView(R.id.tab_layout) TabLayout tabLayout;
+    @BindView(R.id.view_pager) ViewPager2 viewPager;
+
+    private final RouterStateAdapter pagerAdapter;
+
+    public ViewPager2Controller() {
+        pagerAdapter = new RouterStateAdapter(this) {
+            @Override
+            public void configureRouter(@NonNull Router router, int position) {
+                if (!router.hasRootController()) {
+                    Controller page = new ChildController(String.format(Locale.getDefault(), "Child #%d (Swipe to see more)", position), PAGE_COLORS[position], true);
+                    router.setRoot(RouterTransaction.with(page));
+                }
+            }
+
+            @Override
+            public int getItemCount() {
+                return PAGE_COLORS.length;
+            }
+        };
+    }
+
+    @NonNull
+    @Override
+    protected View inflateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container) {
+        return inflater.inflate(R.layout.controller_view_pager2, container, false);
+    }
+
+    @Override
+    protected void onViewBound(@NonNull View view) {
+        super.onViewBound(view);
+        viewPager.setAdapter(pagerAdapter);
+        new TabLayoutMediator(tabLayout, viewPager, (tab, position) -> tab.setText("Page " + position)).attach();
+    }
+
+    @Override
+    protected void onDestroyView(@NonNull View view) {
+        if (!getActivity().isChangingConfigurations()) {
+            viewPager.setAdapter(null);
+        }
+        tabLayout.setupWithViewPager(null);
+        super.onDestroyView(view);
+    }
+
+    @Override
+    protected String getTitle() {
+        return "ViewPager2 Demo";
+    }
+
+}

demo/src/main/java/com/bluelinelabs/conductor/demo/controllers/ViewPagerController.java

@@ -1,24 +1,25 @@
 package com.bluelinelabs.conductor.demo.controllers;
 
-import androidx.annotation.NonNull;
-import com.google.android.material.tabs.TabLayout;
-import androidx.viewpager.widget.ViewPager;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 
+import androidx.annotation.NonNull;
+import androidx.viewpager.widget.ViewPager;
+
 import com.bluelinelabs.conductor.Controller;
 import com.bluelinelabs.conductor.Router;
 import com.bluelinelabs.conductor.RouterTransaction;
 import com.bluelinelabs.conductor.demo.R;
 import com.bluelinelabs.conductor.demo.controllers.base.BaseController;
 import com.bluelinelabs.conductor.viewpager.RouterPagerAdapter;
+import com.google.android.material.tabs.TabLayout;
 
 import java.util.Locale;
 
 import butterknife.BindView;
 
-public class PagerController extends BaseController {
+public class ViewPagerController extends BaseController {
 
     private int[] PAGE_COLORS = new int[]{R.color.green_300, R.color.cyan_300, R.color.deep_purple_300, R.color.lime_300, R.color.red_300};
 
@@ -27,7 +28,7 @@ public class PagerController extends BaseController {
 
     private final RouterPagerAdapter pagerAdapter;
 
-    public PagerController() {
+    public ViewPagerController() {
         pagerAdapter = new RouterPagerAdapter(this) {
             @Override
             public void configureRouter(@NonNull Router router, int position) {
@@ -52,7 +53,7 @@ public class PagerController extends BaseController {
     @NonNull
     @Override
     protected View inflateView(@NonNull LayoutInflater inflater, @NonNull ViewGroup container) {
-        return inflater.inflate(R.layout.controller_pager, container, false);
+        return inflater.inflate(R.layout.controller_view_pager, container, false);
     }
 
     @Override

demo/src/main/res/layout/controller_view_pager2.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <com.google.android.material.tabs.TabLayout
+        android:id="@+id/tab_layout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:background="?attr/colorPrimary"
+        android:elevation="6dp"
+        android:minHeight="?attr/actionBarSize"
+        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
+        tools:targetApi="lollipop"
+        />
+
+    <androidx.viewpager2.widget.ViewPager2
+        android:id="@+id/view_pager"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        />
+
+</LinearLayout>

dependencies.gradle

@@ -13,17 +13,23 @@ ext {
     autodisposeVersion = '1.0.0'
     archComponentsVersion = '2.0.0'
     junitVersion = '4.12'
-    lintVersion = '26.6.1'
     mvnPublishVersion = '0.11.1'
 
-    kotlinVersion = '1.3.71'
+    agpVersion = "4.1.0"
+    lintVersion = agpVersion.replaceFirst(~/\d*/) { version ->
+        // the major version of lint is always 23 version higher than the major version of agp
+        version.toInteger() + 23
+    }
+
+    kotlinVersion = '1.3.72'
     kotlinStd = "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlinVersion"
 
-    material = "com.google.android.material:material:1.0.0"
+    material = "com.google.android.material:material:1.1.0"
     androidxAnnotations = "androidx.annotation:annotation:1.1.0"
     androidxAppCompat = "androidx.appcompat:appcompat:1.0.0"
     androidxTransition = "androidx.transition:transition:1.3.1"
     androidxCollection = "androidx.collection:collection:1.1.0"
+    androidxViewPager2 = "androidx.viewpager2:viewpager2:1.0.0"
 
     butterknife = "com.jakewharton:butterknife:$butterknifeVersion"
     butterknifeCompiler = "com.jakewharton:butterknife-compiler:$butterknifeVersion"

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

gradlew

@@ -82,6 +82,7 @@ esac
 
 CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
 
+
 # Determine the Java command to use to start the JVM.
 if [ -n "$JAVA_HOME" ] ; then
     if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
@@ -129,6 +130,7 @@ fi
 if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
     APP_HOME=`cygpath --path --mixed "$APP_HOME"`
     CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+
     JAVACMD=`cygpath --unix "$JAVACMD"`
 
     # We build the pattern for arguments to be converted via cygpath

gradlew.bat

@@ -40,7 +40,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto init
+if "%ERRORLEVEL%" == "0" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -54,7 +54,7 @@ goto fail
 set JAVA_HOME=%JAVA_HOME:"=%
 set JAVA_EXE=%JAVA_HOME%/bin/java.exe
 
-if exist "%JAVA_EXE%" goto init
+if exist "%JAVA_EXE%" goto execute
 
 echo.
 echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
@@ -64,28 +64,14 @@ echo location of your Java installation.
 
 goto fail
 
-:init
-@rem Get command-line arguments, handling Windows variants
-
-if not "%OS%" == "Windows_NT" goto win9xME_args
-
-:win9xME_args
-@rem Slurp the command line arguments.
-set CMD_LINE_ARGS=
-set _SKIP=2
-
-:win9xME_args_slurp
-if "x%~1" == "x" goto execute
-
-set CMD_LINE_ARGS=%*
-
 :execute
 @rem Setup the command line
 
 set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
+
 @rem Execute Gradle
-"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %CMD_LINE_ARGS%
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
 
 :end
 @rem End local scope for the variables with windows NT shell

settings.gradle

@@ -1,9 +1,9 @@
 include ':conductor'
 include ':conductor-lint'
 include ':conductor-modules:viewpager'
+include ':conductor-modules:viewpager2'
 include ':conductor-modules:rxlifecycle2'
 include ':conductor-modules:autodispose'
 include ':conductor-modules:arch-components-lifecycle'
-include ':conductor-modules:transition-platform'
-include ':conductor-modules:transition-androidx'
+include ':conductor-modules:androidx-transition'
 include ':demo'