From 04ce366cbe92ab2dbbfc8cef9c1c4c50334f762e Mon Sep 17 00:00:00 2001 From: Website Deployment Script Date: Fri, 1 Jul 2016 02:42:49 +0000 Subject: [PATCH] Updated docs for next --- releases/next/docs/accessibility.html | 2 +- releases/next/docs/actionsheetios.html | 2 +- releases/next/docs/activityindicator.html | 2 +- releases/next/docs/alert.html | 2 +- releases/next/docs/alertios.html | 2 +- .../docs/android-building-from-source.html | 2 +- .../next/docs/android-ui-performance.html | 2 +- releases/next/docs/animated.html | 2 +- releases/next/docs/animations.html | 2 +- releases/next/docs/appregistry.html | 2 +- releases/next/docs/appstate.html | 2 +- releases/next/docs/asyncstorage.html | 2 +- releases/next/docs/backandroid.html | 2 +- releases/next/docs/cameraroll.html | 2 +- releases/next/docs/clipboard.html | 2 +- releases/next/docs/colors.html | 2 +- releases/next/docs/communication-ios.html | 2 +- releases/next/docs/datepickerandroid.html | 2 +- releases/next/docs/datepickerios.html | 2 +- releases/next/docs/debugging.html | 2 +- releases/next/docs/dimensions.html | 2 +- releases/next/docs/direct-manipulation.html | 2 +- releases/next/docs/drawerlayoutandroid.html | 2 +- releases/next/docs/flexbox.html | 2 +- releases/next/docs/geolocation.html | 2 +- .../next/docs/gesture-responder-system.html | 2 +- releases/next/docs/getting-started.html | 2 +- releases/next/docs/handling-text-input.html | 2 +- releases/next/docs/handling-touches.html | 2 +- releases/next/docs/height-and-width.html | 2 +- releases/next/docs/image.html | 2 +- releases/next/docs/images.html | 2 +- .../docs/integration-with-existing-apps.html | 2 +- releases/next/docs/intentandroid.html | 2 +- releases/next/docs/interactionmanager.html | 2 +- .../next/docs/javascript-environment.html | 2 +- releases/next/docs/layout-props.html | 2 +- releases/next/docs/layoutanimation.html | 2 +- releases/next/docs/linking-libraries-ios.html | 2 +- releases/next/docs/linking.html | 2 +- releases/next/docs/listview.html | 2 +- releases/next/docs/listviewdatasource.html | 2 +- releases/next/docs/mapview.html | 2 +- releases/next/docs/modal.html | 2 +- releases/next/docs/more-resources.html | 2 +- .../next/docs/native-components-android.html | 2 +- releases/next/docs/native-components-ios.html | 2 +- .../next/docs/native-modules-android.html | 2 +- releases/next/docs/native-modules-ios.html | 2 +- releases/next/docs/nativemethodsmixin.html | 2 +- ...igator-comparison.html => navigation.html} | 80 ++---------- releases/next/docs/navigator.html | 2 +- releases/next/docs/navigatorios.html | 2 +- releases/next/docs/netinfo.html | 2 +- releases/next/docs/network.html | 11 +- releases/next/docs/panresponder.html | 2 +- releases/next/docs/performance.html | 2 +- releases/next/docs/picker.html | 2 +- releases/next/docs/pickerios.html | 2 +- releases/next/docs/pixelratio.html | 2 +- .../next/docs/platform-specific-code.html | 2 +- releases/next/docs/progressbarandroid.html | 2 +- releases/next/docs/progressviewios.html | 2 +- releases/next/docs/props.html | 2 +- releases/next/docs/pushnotificationios.html | 2 +- releases/next/docs/refreshcontrol.html | 2 +- .../next/docs/running-on-device-android.html | 2 +- releases/next/docs/running-on-device-ios.html | 2 +- .../next/docs/running-on-simulator-ios.html | 2 +- releases/next/docs/scrollview.html | 2 +- releases/next/docs/segmentedcontrolios.html | 2 +- releases/next/docs/shadow-props.html | 2 +- releases/next/docs/signed-apk-android.html | 2 +- releases/next/docs/slider.html | 2 +- releases/next/docs/sliderios.html | 2 +- releases/next/docs/state.html | 2 +- releases/next/docs/statusbar.html | 2 +- releases/next/docs/statusbarios.html | 2 +- releases/next/docs/style.html | 2 +- releases/next/docs/stylesheet.html | 2 +- releases/next/docs/switch.html | 2 +- releases/next/docs/tabbarios-item.html | 2 +- releases/next/docs/tabbarios.html | 2 +- releases/next/docs/testing.html | 2 +- releases/next/docs/text.html | 2 +- releases/next/docs/textinput.html | 2 +- releases/next/docs/timepickerandroid.html | 2 +- releases/next/docs/timers.html | 2 +- releases/next/docs/toastandroid.html | 2 +- releases/next/docs/toolbarandroid.html | 2 +- releases/next/docs/touchablehighlight.html | 2 +- .../next/docs/touchablenativefeedback.html | 2 +- releases/next/docs/touchableopacity.html | 2 +- .../next/docs/touchablewithoutfeedback.html | 2 +- releases/next/docs/transforms.html | 2 +- releases/next/docs/troubleshooting.html | 2 +- releases/next/docs/tutorial.html | 2 +- releases/next/docs/upgrading.html | 2 +- releases/next/docs/using-a-listview.html | 2 +- releases/next/docs/using-a-scrollview.html | 2 +- releases/next/docs/using-navigators.html | 116 ++++++++++++++++++ releases/next/docs/vibration.html | 2 +- releases/next/docs/vibrationios.html | 2 +- releases/next/docs/view.html | 2 +- releases/next/docs/viewpagerandroid.html | 2 +- releases/next/docs/webview.html | 2 +- 106 files changed, 236 insertions(+), 177 deletions(-) rename releases/next/docs/{navigator-comparison.html => navigation.html} (55%) create mode 100644 releases/next/docs/using-navigators.html diff --git a/releases/next/docs/accessibility.html b/releases/next/docs/accessibility.html index 62d3f2e18a5..77d5d92cd0a 100644 --- a/releases/next/docs/accessibility.html +++ b/releases/next/docs/accessibility.html @@ -1,4 +1,4 @@ -Accessibility – React Native | A framework for building native apps using React
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Accessibility #

Edit on GitHub

Native App Accessibility (iOS and Android) #

Both iOS and Android provide APIs for making apps accessible to people with disabilities. In addition, both platforms provide bundled assistive technologies, like the screen readers VoiceOver (iOS) and TalkBack (Android) for the visually impaired. Similarly, in React Native we have included APIs designed to provide developers with support for making apps more accessible. Take note, iOS and Android differ slightly in their approaches, and thus the React Native implementations may vary by platform.

Making Apps Accessible #

Accessibility properties #

accessible (iOS, Android) #

When true, indicates that the view is an accessibility element. When a view is an accessibility element, it groups its children into a single selectable component. By default, all touchable elements are accessible.

On Android, ‘accessible={true}’ property for a react-native View will be translated into native ‘focusable={true}’.

<View accessible={true}> +Accessibility – React Native | A framework for building native apps using React
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Accessibility #

Edit on GitHub

Native App Accessibility (iOS and Android) #

Both iOS and Android provide APIs for making apps accessible to people with disabilities. In addition, both platforms provide bundled assistive technologies, like the screen readers VoiceOver (iOS) and TalkBack (Android) for the visually impaired. Similarly, in React Native we have included APIs designed to provide developers with support for making apps more accessible. Take note, iOS and Android differ slightly in their approaches, and thus the React Native implementations may vary by platform.

Making Apps Accessible #

Accessibility properties #

accessible (iOS, Android) #

When true, indicates that the view is an accessibility element. When a view is an accessibility element, it groups its children into a single selectable component. By default, all touchable elements are accessible.

On Android, ‘accessible={true}’ property for a react-native View will be translated into native ‘focusable={true}’.

<View accessible={true}> <Text>text one</Text> <Text>text two</Text> </View>

In the above example, we can't get accessibility focus separately on 'text one' and 'text two'. Instead we get focus on a parent view with 'accessible' property.

accessibilityLabel (iOS, Android) #

When a view is marked as accessible, it is a good practice to set an accessibilityLabel on the view, so that people who use VoiceOver know what element they have selected. VoiceOver will read this string when a user selects the associated element.

To use, set the accessibilityLabel property to a custom string on your View:

<TouchableOpacity accessible={true} accessibilityLabel={'Tap me!'} onPress={this._onPress}> diff --git a/releases/next/docs/actionsheetios.html b/releases/next/docs/actionsheetios.html index 2ac5d4e3a9a..39083cd179e 100644 --- a/releases/next/docs/actionsheetios.html +++ b/releases/next/docs/actionsheetios.html @@ -1,4 +1,4 @@ -ActionSheetIOS – React Native | A framework for building native apps using React
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ActionSheetIOS #

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Methods #

static showActionSheetWithOptions(options, callback) #

Display an iOS action sheet. The options object must contain one or more +ActionSheetIOS – React Native | A framework for building native apps using React

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ActionSheetIOS #

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Methods #

static showActionSheetWithOptions(options, callback) #

Display an iOS action sheet. The options object must contain one or more of:

  • options (array of strings) - a list of button titles (required)
  • cancelButtonIndex (int) - index of cancel button in options
  • destructiveButtonIndex (int) - index of destructive button in options
  • title (string) - a title to show above the action sheet
  • message (string) - a message to show below the title

static showShareActionSheetWithOptions(options, failureCallback, successCallback) #

Display the iOS share sheet. The options object should contain one or both of message and url and can additionally have a subject or excludedActivityTypes:

  • url (string) - a URL to share
  • message (string) - a message to share
  • subject (string) - a subject for the message
  • excludedActivityTypes (array) - the activites to exclude from the ActionSheet

NOTE: if url points to a local file, or is a base64-encoded diff --git a/releases/next/docs/activityindicator.html b/releases/next/docs/activityindicator.html index e77ecbb68bf..980634d2b7d 100644 --- a/releases/next/docs/activityindicator.html +++ b/releases/next/docs/activityindicator.html @@ -1,4 +1,4 @@ -ActivityIndicator – React Native | A framework for building native apps using React

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ActivityIndicator #

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Displays a circular loading indicator.

Props #

View props... #

animating bool #

Whether to show the indicator (true, the default) or hide it (false).

color color #

The foreground color of the spinner (default is gray).

size enum('small', 'large') #

Size of the indicator. Small has a height of 20, large has a height of 36. +ActivityIndicator – React Native | A framework for building native apps using React

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ActivityIndicator #

Edit on GitHub

Displays a circular loading indicator.

Props #

View props... #

animating bool #

Whether to show the indicator (true, the default) or hide it (false).

color color #

The foreground color of the spinner (default is gray).

size enum('small', 'large') #

Size of the indicator. Small has a height of 20, large has a height of 36. Other sizes can be obtained using a scale transform.

ioshidesWhenStopped bool #

Whether the indicator should hide when not animating (true by default).

Examples #

Edit on GitHub
'use strict'; const React = require('react'); diff --git a/releases/next/docs/alert.html b/releases/next/docs/alert.html index 1d0e2d3877c..9391dd1e787 100644 --- a/releases/next/docs/alert.html +++ b/releases/next/docs/alert.html @@ -1,4 +1,4 @@ -Alert – React Native | A framework for building native apps using React
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Alert #

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Launches an alert dialog with the specified title and message.

Optionally provide a list of buttons. Tapping any button will fire the +Alert – React Native | A framework for building native apps using React

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Alert #

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Launches an alert dialog with the specified title and message.

Optionally provide a list of buttons. Tapping any button will fire the respective onPress callback and dismiss the alert. By default, the only button will be an 'OK' button.

This is an API that works both on iOS and Android and can show static alerts. To show an alert that prompts the user to enter some information, diff --git a/releases/next/docs/alertios.html b/releases/next/docs/alertios.html index cfc8b49566b..c88fcdae3c4 100644 --- a/releases/next/docs/alertios.html +++ b/releases/next/docs/alertios.html @@ -1,4 +1,4 @@ -AlertIOS – React Native | A framework for building native apps using React

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AlertIOS #

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AlertIOS provides functionality to create an iOS alert dialog with a +AlertIOS – React Native | A framework for building native apps using React

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AlertIOS #

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AlertIOS provides functionality to create an iOS alert dialog with a message or create a prompt for user input.

Creating an iOS alert:

AlertIOS.alert( 'Sync Complete', 'All your data are belong to us.' diff --git a/releases/next/docs/android-building-from-source.html b/releases/next/docs/android-building-from-source.html index 7971bcd9cf2..22f6f552a5a 100644 --- a/releases/next/docs/android-building-from-source.html +++ b/releases/next/docs/android-building-from-source.html @@ -1,4 +1,4 @@ -Building React Native from source – React Native | A framework for building native apps using React
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Building React Native from source #

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You will need to build React Native from source if you want to work on a new feature/bug fix, try out the latest features which are not released yet, or maintain your own fork with patches that cannot be merged to the core.

Prerequisites #

Assuming you have the Android SDK installed, run android to open the Android SDK Manager.

Make sure you have the following installed:

  1. Android SDK version 23 (compileSdkVersion in build.gradle)
  2. SDK build tools version 23.0.1 (buildToolsVersion in build.gradle)
  3. Local Maven repository for Support Libraries (formerly Android Support Repository) >= 17 (for Android Support Library)
  4. Android NDK (download links and installation instructions below)

Point Gradle to your Android SDK: #

Step 1: Set environment variables through your local shell.

Note: Files may vary based on shell flavor. See below for examples from common shells.

  • bash: .bash_profile or .bashrc
  • zsh: .zprofile or .zshrc
  • ksh: .profile or $ENV

Example:

export ANDROID_SDK=/Users/your_unix_name/android-sdk-macosx +Building React Native from source – React Native | A framework for building native apps using React
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Building React Native from source #

Edit on GitHub

You will need to build React Native from source if you want to work on a new feature/bug fix, try out the latest features which are not released yet, or maintain your own fork with patches that cannot be merged to the core.

Prerequisites #

Assuming you have the Android SDK installed, run android to open the Android SDK Manager.

Make sure you have the following installed:

  1. Android SDK version 23 (compileSdkVersion in build.gradle)
  2. SDK build tools version 23.0.1 (buildToolsVersion in build.gradle)
  3. Local Maven repository for Support Libraries (formerly Android Support Repository) >= 17 (for Android Support Library)
  4. Android NDK (download links and installation instructions below)

Point Gradle to your Android SDK: #

Step 1: Set environment variables through your local shell.

Note: Files may vary based on shell flavor. See below for examples from common shells.

  • bash: .bash_profile or .bashrc
  • zsh: .zprofile or .zshrc
  • ksh: .profile or $ENV

Example:

export ANDROID_SDK=/Users/your_unix_name/android-sdk-macosx export ANDROID_NDK=/Users/your_unix_name/android-ndk/android-ndk-r10e

Step 2: Create a local.properties file in the android directory of your react-native app with the following contents:

Example:

sdk.dir=/Users/your_unix_name/android-sdk-macosx ndk.dir=/Users/your_unix_name/android-ndk/android-ndk-r10e

Download links for Android NDK #

  1. Mac OS (64-bit) - http://dl.google.com/android/repository/android-ndk-r10e-darwin-x86_64.zip
  2. Linux (64-bit) - http://dl.google.com/android/repository/android-ndk-r10e-linux-x86_64.zip
  3. Windows (64-bit) - http://dl.google.com/android/repository/android-ndk-r10e-windows-x86_64.zip
  4. Windows (32-bit) - http://dl.google.com/android/repository/android-ndk-r10e-windows-x86.zip

You can find further instructions on the official page.

Building the source #

1. Installing the fork #

First, you need to install react-native from your fork. For example, to install the master branch from the official repo, run the following:

npm install --save github:facebook/react-native#master

Alternatively, you can clone the repo to your node_modules directory and run npm install inside the cloned repo.

2. Adding gradle dependencies #

Add gradle-download-task as dependency in android/build.gradle:

... dependencies { diff --git a/releases/next/docs/android-ui-performance.html b/releases/next/docs/android-ui-performance.html index 893838c3747..929afb620fb 100644 --- a/releases/next/docs/android-ui-performance.html +++ b/releases/next/docs/android-ui-performance.html @@ -1,4 +1,4 @@ -Profiling Android UI Performance – React Native | A framework for building native apps using React
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Profiling Android UI Performance #

Edit on GitHub

We try our best to deliver buttery-smooth UI performance by default, but sometimes that just isn't possible. Remember, Android supports 10k+ different phones and is generalized to support software rendering: the framework architecture and need to generalize across many hardware targets unfortunately means you get less for free relative to iOS. But sometimes, there are things you can improve (and many times it's not native code's fault at all!).

The first step for debugging this jank is to answer the fundamental question of where your time is being spent during each 16ms frame. For that, we'll be using a standard Android profiling tool called systrace. But first...

Make sure that JS dev mode is OFF!

You should see __DEV__ === false, development-level warning are OFF, performance optimizations are ON in your application logs (which you can view using adb logcat)

Profiling with Systrace #

Systrace is a standard Android marker-based profiling tool (and is installed when you install the Android platform-tools package). Profiled code blocks are surrounded by markers start/end markers which are then visualized in a colorful chart format. Both the Android SDK and React Native framework provide standard markers that you can visualize.

Collecting a trace #

NOTE:

Systrace support was added in react-native v0.15. You will need to build with that version to collect a trace.

First, connect a device that exhibits the stuttering you want to investigate to your computer via USB and get it to the point right before the navigation/animation you want to profile. Run systrace as follows

$ <path_to_android_sdk>/platform-tools/systrace/systrace.py --time=10 -o trace.html sched gfx view -a <your_package_name>

A quick breakdown of this command:

  • time is the length of time the trace will be collected in seconds
  • sched, gfx, and view are the android SDK tags (collections of markers) we care about: sched gives you information about what's running on each core of your phone, gfx gives you graphics info such as frame boundaries, and view gives you information about measure, layout, and draw passes
  • -a <your_package_name> enables app-specific markers, specifically the ones built into the React Native framework. your_package_name can be found in the AndroidManifest.xml of your app and looks like com.example.app

Once the trace starts collecting, perform the animation or interaction you care about. At the end of the trace, systrace will give you a link to the trace which you can open in your browser.

Reading the trace #

After opening the trace in your browser (preferably Chrome), you should see something like this:

Example

HINT: Use the WASD keys to strafe and zoom

Enable VSync highlighting #

The first thing you should do is highlight the 16ms frame boundaries if you haven't already done that. Check this checkbox at the top right of the screen:

Enable VSync Highlighting

You should see zebra stripes as in the screenshot above. If you don't, try profiling on a different device: Samsung has been known to have issues displaying vsyncs while the Nexus series is generally pretty reliable.

Find your process #

Scroll until you see (part of) the name of your package. In this case, I was profiling com.facebook.adsmanager, which shows up as book.adsmanager because of silly thread name limits in the kernel.

On the left side, you'll see a set of threads which correspond to the timeline rows on the right. There are three/four threads we care about for our purposes: the UI thread (which has your package name or the name UI Thread), mqt_js and mqt_native_modules. If you're running on Android 5+, we also care about the Render Thread.

UI Thread #

This is where standard android measure/layout/draw happens. The thread name on the right will be your package name (in my case book.adsmanager) or UI Thread. The events that you see on this thread should look something like this and have to do with Choreographer, traversals, and DispatchUI:

UI Thread Example

JS Thread #

This is where JS is executed. The thread name will be either mqt_js or <...> depending on how cooperative the kernel on your device is being. To identify it if it doesn't have a name, look for things like JSCall, Bridge.executeJSCall, etc:

JS Thread Example

Native Modules Thread #

This is where native module calls (e.g. the UIManager) are executed. The thread name will be either mqt_native_modules or <...>. To identify it in the latter case, look for things like NativeCall, callJavaModuleMethod, and onBatchComplete:

Native Modules Thread Example

Bonus: Render Thread #

If you're using Android L (5.0) and up, you will also have a render thread in your application. This thread generates the actual OpenGL commands used to draw your UI. The thread name will be either RenderThread or <...>. To identify it in the latter case, look for things like DrawFrame and queueBuffer:

Render Thread Example

Identifying a culprit #

A smooth animation should look something like the following:

Smooth Animation

Each change in color is a frame -- remember that in order to display a frame, all our UI work needs to be done by the end of that 16ms period. Notice that no thread is working close to the frame boundary. An application rendering like this is rendering at 60FPS.

If you noticed chop, however, you might see something like this:

Choppy Animation from JS

Notice that the JS thread is executing basically all the time, and across frame boundaries! This app is not rendering at 60FPS. In this case, the problem lies in JS.

You might also see something like this:

Choppy Animation from UI

In this case, the UI and render threads are the ones that have work crossing frame boundaries. The UI that we're trying to render on each frame is requiring too much work to be done. In this case, the problem lies in the native views being rendered.

At this point, you'll have some very helpful information to inform your next steps.

JS Issues #

If you identified a JS problem, look for clues in the specific JS that you're executing. In the scenario above, we see RCTEventEmitter being called multiple times per frame. Here's a zoom-in of the JS thread from the trace above:

Too much JS

This doesn't seem right. Why is it being called so often? Are they actually different events? The answers to these questions will probably depend on your product code. And many times, you'll want to look into shouldComponentUpdate.

TODO: Add more tools for profiling JS

Native UI Issues #

If you identified a native UI problem, there are usually two scenarios:

  1. the UI you're trying to draw each frame involves to much work on the GPU, or
  2. You're constructing new UI during the animation/interaction (e.g. loading in new content during a scroll).

Too much GPU work #

In the first scenario, you'll see a trace that has the UI thread and/or Render Thread looking like this:

Overloaded GPU

Notice the long amount of time spent in DrawFrame that crosses frame boundaries. This is time spent waiting for the GPU to drain its command buffer from the previous frame.

To mitigate this, you should:

  • investigate using renderToHardwareTextureAndroid for complex, static content that is being animated/transformed (e.g. the Navigator slide/alpha animations)
  • make sure that you are not using needsOffscreenAlphaCompositing, which is disabled by default, as it greatly increases the per-frame load on the GPU in most cases.

If these don't help and you want to dig deeper into what the GPU is actually doing, you can check out Tracer for OpenGL ES.

Creating new views on the UI thread #

In the second scenario, you'll see something more like this:

Creating Views

Notice that first the JS thread thinks for a bit, then you see some work done on the native modules thread, followed by an expensive traversal on the UI thread.

There isn't an easy way to mitigate this unless you're able to postpone creating new UI until after the interaction, or you are able to simplify the UI you're creating. The react native team is working on a infrastructure level solution for this that will allow new UI to be created and configured off the main thread, allowing the interaction to continue smoothly.

Still stuck? #

If you are confused or stuck, please post ask on Stack Overflow with the react-native tag. If you are unable to get a response there, or find an issue with a core component, please File a Github issue.

Next →
© 2016 Facebook Inc.
React Nativenext

The Basics

Guides

Guides (iOS)

Guides (Android)

components

apis

Profiling Android UI Performance #

Edit on GitHub

We try our best to deliver buttery-smooth UI performance by default, but sometimes that just isn't possible. Remember, Android supports 10k+ different phones and is generalized to support software rendering: the framework architecture and need to generalize across many hardware targets unfortunately means you get less for free relative to iOS. But sometimes, there are things you can improve (and many times it's not native code's fault at all!).

The first step for debugging this jank is to answer the fundamental question of where your time is being spent during each 16ms frame. For that, we'll be using a standard Android profiling tool called systrace. But first...

Make sure that JS dev mode is OFF!

You should see __DEV__ === false, development-level warning are OFF, performance optimizations are ON in your application logs (which you can view using adb logcat)

Profiling with Systrace #

Systrace is a standard Android marker-based profiling tool (and is installed when you install the Android platform-tools package). Profiled code blocks are surrounded by markers start/end markers which are then visualized in a colorful chart format. Both the Android SDK and React Native framework provide standard markers that you can visualize.

Collecting a trace #

NOTE:

Systrace support was added in react-native v0.15. You will need to build with that version to collect a trace.

First, connect a device that exhibits the stuttering you want to investigate to your computer via USB and get it to the point right before the navigation/animation you want to profile. Run systrace as follows

$ <path_to_android_sdk>/platform-tools/systrace/systrace.py --time=10 -o trace.html sched gfx view -a <your_package_name>

A quick breakdown of this command:

  • time is the length of time the trace will be collected in seconds
  • sched, gfx, and view are the android SDK tags (collections of markers) we care about: sched gives you information about what's running on each core of your phone, gfx gives you graphics info such as frame boundaries, and view gives you information about measure, layout, and draw passes
  • -a <your_package_name> enables app-specific markers, specifically the ones built into the React Native framework. your_package_name can be found in the AndroidManifest.xml of your app and looks like com.example.app

Once the trace starts collecting, perform the animation or interaction you care about. At the end of the trace, systrace will give you a link to the trace which you can open in your browser.

Reading the trace #

After opening the trace in your browser (preferably Chrome), you should see something like this:

Example

HINT: Use the WASD keys to strafe and zoom

Enable VSync highlighting #

The first thing you should do is highlight the 16ms frame boundaries if you haven't already done that. Check this checkbox at the top right of the screen:

Enable VSync Highlighting

You should see zebra stripes as in the screenshot above. If you don't, try profiling on a different device: Samsung has been known to have issues displaying vsyncs while the Nexus series is generally pretty reliable.

Find your process #

Scroll until you see (part of) the name of your package. In this case, I was profiling com.facebook.adsmanager, which shows up as book.adsmanager because of silly thread name limits in the kernel.

On the left side, you'll see a set of threads which correspond to the timeline rows on the right. There are three/four threads we care about for our purposes: the UI thread (which has your package name or the name UI Thread), mqt_js and mqt_native_modules. If you're running on Android 5+, we also care about the Render Thread.

UI Thread #

This is where standard android measure/layout/draw happens. The thread name on the right will be your package name (in my case book.adsmanager) or UI Thread. The events that you see on this thread should look something like this and have to do with Choreographer, traversals, and DispatchUI:

UI Thread Example

JS Thread #

This is where JS is executed. The thread name will be either mqt_js or <...> depending on how cooperative the kernel on your device is being. To identify it if it doesn't have a name, look for things like JSCall, Bridge.executeJSCall, etc:

JS Thread Example

Native Modules Thread #

This is where native module calls (e.g. the UIManager) are executed. The thread name will be either mqt_native_modules or <...>. To identify it in the latter case, look for things like NativeCall, callJavaModuleMethod, and onBatchComplete:

Native Modules Thread Example

Bonus: Render Thread #

If you're using Android L (5.0) and up, you will also have a render thread in your application. This thread generates the actual OpenGL commands used to draw your UI. The thread name will be either RenderThread or <...>. To identify it in the latter case, look for things like DrawFrame and queueBuffer:

Render Thread Example

Identifying a culprit #

A smooth animation should look something like the following:

Smooth Animation

Each change in color is a frame -- remember that in order to display a frame, all our UI work needs to be done by the end of that 16ms period. Notice that no thread is working close to the frame boundary. An application rendering like this is rendering at 60FPS.

If you noticed chop, however, you might see something like this:

Choppy Animation from JS

Notice that the JS thread is executing basically all the time, and across frame boundaries! This app is not rendering at 60FPS. In this case, the problem lies in JS.

You might also see something like this:

Choppy Animation from UI

In this case, the UI and render threads are the ones that have work crossing frame boundaries. The UI that we're trying to render on each frame is requiring too much work to be done. In this case, the problem lies in the native views being rendered.

At this point, you'll have some very helpful information to inform your next steps.

JS Issues #

If you identified a JS problem, look for clues in the specific JS that you're executing. In the scenario above, we see RCTEventEmitter being called multiple times per frame. Here's a zoom-in of the JS thread from the trace above:

Too much JS

This doesn't seem right. Why is it being called so often? Are they actually different events? The answers to these questions will probably depend on your product code. And many times, you'll want to look into shouldComponentUpdate.

TODO: Add more tools for profiling JS

Native UI Issues #

If you identified a native UI problem, there are usually two scenarios:

  1. the UI you're trying to draw each frame involves to much work on the GPU, or
  2. You're constructing new UI during the animation/interaction (e.g. loading in new content during a scroll).

Too much GPU work #

In the first scenario, you'll see a trace that has the UI thread and/or Render Thread looking like this:

Overloaded GPU

Notice the long amount of time spent in DrawFrame that crosses frame boundaries. This is time spent waiting for the GPU to drain its command buffer from the previous frame.

To mitigate this, you should:

  • investigate using renderToHardwareTextureAndroid for complex, static content that is being animated/transformed (e.g. the Navigator slide/alpha animations)
  • make sure that you are not using needsOffscreenAlphaCompositing, which is disabled by default, as it greatly increases the per-frame load on the GPU in most cases.

If these don't help and you want to dig deeper into what the GPU is actually doing, you can check out Tracer for OpenGL ES.

Creating new views on the UI thread #

In the second scenario, you'll see something more like this:

Creating Views

Notice that first the JS thread thinks for a bit, then you see some work done on the native modules thread, followed by an expensive traversal on the UI thread.

There isn't an easy way to mitigate this unless you're able to postpone creating new UI until after the interaction, or you are able to simplify the UI you're creating. The react native team is working on a infrastructure level solution for this that will allow new UI to be created and configured off the main thread, allowing the interaction to continue smoothly.

Still stuck? #

If you are confused or stuck, please post ask on Stack Overflow with the react-native tag. If you are unable to get a response there, or find an issue with a core component, please File a Github issue.

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Animated #

Edit on GitHub

Animations are an important part of modern UX, and the Animated +Animated – React Native | A framework for building native apps using React

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Animated #

Edit on GitHub

Animations are an important part of modern UX, and the Animated library is designed to make them fluid, powerful, and easy to build and maintain.

The simplest workflow is to create an Animated.Value, hook it up to one or more style attributes of an animated component, and then drive updates either diff --git a/releases/next/docs/animations.html b/releases/next/docs/animations.html index 1d6cecca01c..4a91859c38c 100644 --- a/releases/next/docs/animations.html +++ b/releases/next/docs/animations.html @@ -1,4 +1,4 @@ -Animations – React Native | A framework for building native apps using React

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Animations #

Edit on GitHub

Fluid, meaningful animations are essential to the mobile user experience. Like +Animations – React Native | A framework for building native apps using React

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Animations #

Edit on GitHub

Fluid, meaningful animations are essential to the mobile user experience. Like everything in React Native, Animation APIs for React Native are currently under development, but have started to coalesce around two complementary systems: LayoutAnimation for animated global layout transactions, and Animated for diff --git a/releases/next/docs/appregistry.html b/releases/next/docs/appregistry.html index 7e2f4d6dc4d..f171b4634d9 100644 --- a/releases/next/docs/appregistry.html +++ b/releases/next/docs/appregistry.html @@ -1,4 +1,4 @@ -AppRegistry – React Native | A framework for building native apps using React

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AppRegistry #

Edit on GitHub

AppRegistry is the JS entry point to running all React Native apps. App +AppRegistry – React Native | A framework for building native apps using React

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AppRegistry #

Edit on GitHub

AppRegistry is the JS entry point to running all React Native apps. App root components should register themselves with AppRegistry.registerComponent, then the native system can load the bundle for the app and then actually run the app when it's ready by invoking diff --git a/releases/next/docs/appstate.html b/releases/next/docs/appstate.html index faad2f0b767..a4dc0dbd995 100644 --- a/releases/next/docs/appstate.html +++ b/releases/next/docs/appstate.html @@ -1,4 +1,4 @@ -AppState – React Native | A framework for building native apps using React

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AppState #

Edit on GitHub

AppState can tell you if the app is in the foreground or background, +AppState – React Native | A framework for building native apps using React

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AppState #

Edit on GitHub

AppState can tell you if the app is in the foreground or background, and notify you when the state changes.

AppState is frequently used to determine the intent and proper behavior when handling push notifications.

App States #

  • active - The app is running in the foreground
  • background - The app is running in the background. The user is either in another app or on the home screen
  • inactive - This is a state that occurs when transitioning between diff --git a/releases/next/docs/asyncstorage.html b/releases/next/docs/asyncstorage.html index 583566e0325..a815ae14fcf 100644 --- a/releases/next/docs/asyncstorage.html +++ b/releases/next/docs/asyncstorage.html @@ -1,4 +1,4 @@ -AsyncStorage – React Native | A framework for building native apps using React
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    AsyncStorage #

    		Edit on GitHub

    AsyncStorage is a simple, asynchronous, persistent, key-value storage +AsyncStorage – React Native | A framework for building native apps using React

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    AsyncStorage #

    		Edit on GitHub

    AsyncStorage is a simple, asynchronous, persistent, key-value storage system that is global to the app. It should be used instead of LocalStorage.

    It is recommended that you use an abstraction on top of AsyncStorage instead of AsyncStorage directly for anything more than light usage since it operates globally.

    On iOS, AsyncStorage is backed by native code that stores small values in a diff --git a/releases/next/docs/backandroid.html b/releases/next/docs/backandroid.html index b6d21a66731..f98c7ecad8c 100644 --- a/releases/next/docs/backandroid.html +++ b/releases/next/docs/backandroid.html @@ -1,4 +1,4 @@ -BackAndroid – React Native | A framework for building native apps using React

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    BackAndroid #

    		Edit on GitHub

    Detect hardware back button presses, and programmatically invoke the default back button +BackAndroid – React Native | A framework for building native apps using React

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    BackAndroid #

    		Edit on GitHub

    Detect hardware back button presses, and programmatically invoke the default back button functionality to exit the app if there are no listeners or if none of the listeners return true.

    Example:

    BackAndroid.addEventListener('hardwareBackPress', function() { if (!this.onMainScreen()) { this.goBack(); diff --git a/releases/next/docs/cameraroll.html b/releases/next/docs/cameraroll.html index 1fb61471759..5a7436267a2 100644 --- a/releases/next/docs/cameraroll.html +++ b/releases/next/docs/cameraroll.html @@ -1,4 +1,4 @@ -CameraRoll – React Native | A framework for building native apps using React
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    CameraRoll #

    		Edit on GitHub

    CameraRoll provides access to the local camera roll / gallery.

    Methods #

    static saveImageWithTag(tag) #

    static saveToCameraRoll(tag, type?) #

    Saves the photo or video to the camera roll / gallery.

    On Android, the tag must be a local image or video URI, such as "file:///sdcard/img.png".

    On iOS, the tag can be any image URI (including local, remote asset-library and base64 data URIs) +CameraRoll – React Native | A framework for building native apps using React

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    CameraRoll #

    		Edit on GitHub

    CameraRoll provides access to the local camera roll / gallery.

    Methods #

    static saveImageWithTag(tag) #

    static saveToCameraRoll(tag, type?) #

    Saves the photo or video to the camera roll / gallery.

    On Android, the tag must be a local image or video URI, such as "file:///sdcard/img.png".

    On iOS, the tag can be any image URI (including local, remote asset-library and base64 data URIs) or a local video file URI (remote or data URIs are not supported for saving video at this time).

    If the tag has a file extension of .mov or .mp4, it will be inferred as a video. Otherwise it will be treated as a photo. To override the automatic choice, you can pass an optional type parameter that must be one of 'photo' or 'video'.

    Returns a Promise which will resolve with the new URI.

    static getPhotos(params) #

    Returns a Promise with photo identifier objects from the local camera diff --git a/releases/next/docs/clipboard.html b/releases/next/docs/clipboard.html index c7530d1bdc8..99c4ca6502a 100644 --- a/releases/next/docs/clipboard.html +++ b/releases/next/docs/clipboard.html @@ -1,4 +1,4 @@ -Clipboard – React Native | A framework for building native apps using React

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    Clipboard #

    		Edit on GitHub

    Clipboard gives you an interface for setting and getting content from Clipboard on both iOS and Android

    Methods #

    static getString(0) #

    Get content of string type, this method returns a Promise, so you can use following code to get clipboard content

    async _getContent() { +Clipboard – React Native | A framework for building native apps using React
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    Clipboard #

    		Edit on GitHub

    Clipboard gives you an interface for setting and getting content from Clipboard on both iOS and Android

    Methods #

    static getString(0) #

    Get content of string type, this method returns a Promise, so you can use following code to get clipboard content

    async _getContent() { var content = await Clipboard.getString(); }

    static setString(content) #

    Set content of string type. You can use following code to set clipboard content

    _setContent() { Clipboard.setString('hello world'); diff --git a/releases/next/docs/colors.html b/releases/next/docs/colors.html index d8fb8d3b987..2952036664e 100644 --- a/releases/next/docs/colors.html +++ b/releases/next/docs/colors.html @@ -1,4 +1,4 @@ -Colors – React Native | A framework for building native apps using React
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    Colors #

    		Edit on GitHub

    The following formats are supported:

    • '#f0f' (#rgb)
    • '#f0fc' (#rgba)
    • '#ff00ff' (#rrggbb)
    • '#ff00ff00' (#rrggbbaa)
    • 'rgb(255, 255, 255)'
    • 'rgba(255, 255, 255, 1.0)'
    • 'hsl(360, 100%, 100%)'
    • 'hsla(360, 100%, 100%, 1.0)'
    • 'transparent'
    • 'red'
    • 0xff00ff00 (0xrrggbbaa)

    For the named colors, React Native follows the CSS3 specification:

    • aliceblue (#f0f8ff)
    • antiquewhite (#faebd7)
    • aqua (#00ffff)
    • aquamarine (#7fffd4)
    • azure (#f0ffff)
    • beige (#f5f5dc)
    • bisque (#ffe4c4)
    • black (#000000)
    • blanchedalmond (#ffebcd)
    • blue (#0000ff)
    • blueviolet (#8a2be2)
    • brown (#a52a2a)
    • burlywood (#deb887)
    • cadetblue (#5f9ea0)
    • chartreuse (#7fff00)
    • chocolate (#d2691e)
    • coral (#ff7f50)
    • cornflowerblue (#6495ed)
    • cornsilk (#fff8dc)
    • crimson (#dc143c)
    • cyan (#00ffff)
    • darkblue (#00008b)
    • darkcyan (#008b8b)
    • darkgoldenrod (#b8860b)
    • darkgray (#a9a9a9)
    • darkgreen (#006400)
    • darkgrey (#a9a9a9)
    • darkkhaki (#bdb76b)
    • darkmagenta (#8b008b)
    • darkolivegreen (#556b2f)
    • darkorange (#ff8c00)
    • darkorchid (#9932cc)
    • darkred (#8b0000)
    • darksalmon (#e9967a)
    • darkseagreen (#8fbc8f)
    • darkslateblue (#483d8b)
    • darkslategray (#2f4f4f)
    • darkslategrey (#2f4f4f)
    • darkturquoise (#00ced1)
    • darkviolet (#9400d3)
    • deeppink (#ff1493)
    • deepskyblue (#00bfff)
    • dimgray (#696969)
    • dimgrey (#696969)
    • dodgerblue (#1e90ff)
    • firebrick (#b22222)
    • floralwhite (#fffaf0)
    • forestgreen (#228b22)
    • fuchsia (#ff00ff)
    • gainsboro (#dcdcdc)
    • ghostwhite (#f8f8ff)
    • gold (#ffd700)
    • goldenrod (#daa520)
    • gray (#808080)
    • green (#008000)
    • greenyellow (#adff2f)
    • grey (#808080)
    • honeydew (#f0fff0)
    • hotpink (#ff69b4)
    • indianred (#cd5c5c)
    • indigo (#4b0082)
    • ivory (#fffff0)
    • khaki (#f0e68c)
    • lavender (#e6e6fa)
    • lavenderblush (#fff0f5)
    • lawngreen (#7cfc00)
    • lemonchiffon (#fffacd)
    • lightblue (#add8e6)
    • lightcoral (#f08080)
    • lightcyan (#e0ffff)
    • lightgoldenrodyellow (#fafad2)
    • lightgray (#d3d3d3)
    • lightgreen (#90ee90)
    • lightgrey (#d3d3d3)
    • lightpink (#ffb6c1)
    • lightsalmon (#ffa07a)
    • lightseagreen (#20b2aa)
    • lightskyblue (#87cefa)
    • lightslategray (#778899)
    • lightslategrey (#778899)
    • lightsteelblue (#b0c4de)
    • lightyellow (#ffffe0)
    • lime (#00ff00)
    • limegreen (#32cd32)
    • linen (#faf0e6)
    • magenta (#ff00ff)
    • maroon (#800000)
    • mediumaquamarine (#66cdaa)
    • mediumblue (#0000cd)
    • mediumorchid (#ba55d3)
    • mediumpurple (#9370db)
    • mediumseagreen (#3cb371)
    • mediumslateblue (#7b68ee)
    • mediumspringgreen (#00fa9a)
    • mediumturquoise (#48d1cc)
    • mediumvioletred (#c71585)
    • midnightblue (#191970)
    • mintcream (#f5fffa)
    • mistyrose (#ffe4e1)
    • moccasin (#ffe4b5)
    • navajowhite (#ffdead)
    • navy (#000080)
    • oldlace (#fdf5e6)
    • olive (#808000)
    • olivedrab (#6b8e23)
    • orange (#ffa500)
    • orangered (#ff4500)
    • orchid (#da70d6)
    • palegoldenrod (#eee8aa)
    • palegreen (#98fb98)
    • paleturquoise (#afeeee)
    • palevioletred (#db7093)
    • papayawhip (#ffefd5)
    • peachpuff (#ffdab9)
    • peru (#cd853f)
    • pink (#ffc0cb)
    • plum (#dda0dd)
    • powderblue (#b0e0e6)
    • purple (#800080)
    • rebeccapurple (#663399)
    • red (#ff0000)
    • rosybrown (#bc8f8f)
    • royalblue (#4169e1)
    • saddlebrown (#8b4513)
    • salmon (#fa8072)
    • sandybrown (#f4a460)
    • seagreen (#2e8b57)
    • seashell (#fff5ee)
    • sienna (#a0522d)
    • silver (#c0c0c0)
    • skyblue (#87ceeb)
    • slateblue (#6a5acd)
    • slategray (#708090)
    • slategrey (#708090)
    • snow (#fffafa)
    • springgreen (#00ff7f)
    • steelblue (#4682b4)
    • tan (#d2b48c)
    • teal (#008080)
    • thistle (#d8bfd8)
    • tomato (#ff6347)
    • turquoise (#40e0d0)
    • violet (#ee82ee)
    • wheat (#f5deb3)
    • white (#ffffff)
    • whitesmoke (#f5f5f5)
    • yellow (#ffff00)
    • yellowgreen (#9acd32)
    Next →
    © 2016 Facebook Inc.
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    Colors #

    		Edit on GitHub

    The following formats are supported:

    • '#f0f' (#rgb)
    • '#f0fc' (#rgba)
    • '#ff00ff' (#rrggbb)
    • '#ff00ff00' (#rrggbbaa)
    • 'rgb(255, 255, 255)'
    • 'rgba(255, 255, 255, 1.0)'
    • 'hsl(360, 100%, 100%)'
    • 'hsla(360, 100%, 100%, 1.0)'
    • 'transparent'
    • 'red'
    • 0xff00ff00 (0xrrggbbaa)

    For the named colors, React Native follows the CSS3 specification:

    • aliceblue (#f0f8ff)
    • antiquewhite (#faebd7)
    • aqua (#00ffff)
    • aquamarine (#7fffd4)
    • azure (#f0ffff)
    • beige (#f5f5dc)
    • bisque (#ffe4c4)
    • black (#000000)
    • blanchedalmond (#ffebcd)
    • blue (#0000ff)
    • blueviolet (#8a2be2)
    • brown (#a52a2a)
    • burlywood (#deb887)
    • cadetblue (#5f9ea0)
    • chartreuse (#7fff00)
    • chocolate (#d2691e)
    • coral (#ff7f50)
    • cornflowerblue (#6495ed)
    • cornsilk (#fff8dc)
    • crimson (#dc143c)
    • cyan (#00ffff)
    • darkblue (#00008b)
    • darkcyan (#008b8b)
    • darkgoldenrod (#b8860b)
    • darkgray (#a9a9a9)
    • darkgreen (#006400)
    • darkgrey (#a9a9a9)
    • darkkhaki (#bdb76b)
    • darkmagenta (#8b008b)
    • darkolivegreen (#556b2f)
    • darkorange (#ff8c00)
    • darkorchid (#9932cc)
    • darkred (#8b0000)
    • darksalmon (#e9967a)
    • darkseagreen (#8fbc8f)
    • darkslateblue (#483d8b)
    • darkslategray (#2f4f4f)
    • darkslategrey (#2f4f4f)
    • darkturquoise (#00ced1)
    • darkviolet (#9400d3)
    • deeppink (#ff1493)
    • deepskyblue (#00bfff)
    • dimgray (#696969)
    • dimgrey (#696969)
    • dodgerblue (#1e90ff)
    • firebrick (#b22222)
    • floralwhite (#fffaf0)
    • forestgreen (#228b22)
    • fuchsia (#ff00ff)
    • gainsboro (#dcdcdc)
    • ghostwhite (#f8f8ff)
    • gold (#ffd700)
    • goldenrod (#daa520)
    • gray (#808080)
    • green (#008000)
    • greenyellow (#adff2f)
    • grey (#808080)
    • honeydew (#f0fff0)
    • hotpink (#ff69b4)
    • indianred (#cd5c5c)
    • indigo (#4b0082)
    • ivory (#fffff0)
    • khaki (#f0e68c)
    • lavender (#e6e6fa)
    • lavenderblush (#fff0f5)
    • lawngreen (#7cfc00)
    • lemonchiffon (#fffacd)
    • lightblue (#add8e6)
    • lightcoral (#f08080)
    • lightcyan (#e0ffff)
    • lightgoldenrodyellow (#fafad2)
    • lightgray (#d3d3d3)
    • lightgreen (#90ee90)
    • lightgrey (#d3d3d3)
    • lightpink (#ffb6c1)
    • lightsalmon (#ffa07a)
    • lightseagreen (#20b2aa)
    • lightskyblue (#87cefa)
    • lightslategray (#778899)
    • lightslategrey (#778899)
    • lightsteelblue (#b0c4de)
    • lightyellow (#ffffe0)
    • lime (#00ff00)
    • limegreen (#32cd32)
    • linen (#faf0e6)
    • magenta (#ff00ff)
    • maroon (#800000)
    • mediumaquamarine (#66cdaa)
    • mediumblue (#0000cd)
    • mediumorchid (#ba55d3)
    • mediumpurple (#9370db)
    • mediumseagreen (#3cb371)
    • mediumslateblue (#7b68ee)
    • mediumspringgreen (#00fa9a)
    • mediumturquoise (#48d1cc)
    • mediumvioletred (#c71585)
    • midnightblue (#191970)
    • mintcream (#f5fffa)
    • mistyrose (#ffe4e1)
    • moccasin (#ffe4b5)
    • navajowhite (#ffdead)
    • navy (#000080)
    • oldlace (#fdf5e6)
    • olive (#808000)
    • olivedrab (#6b8e23)
    • orange (#ffa500)
    • orangered (#ff4500)
    • orchid (#da70d6)
    • palegoldenrod (#eee8aa)
    • palegreen (#98fb98)
    • paleturquoise (#afeeee)
    • palevioletred (#db7093)
    • papayawhip (#ffefd5)
    • peachpuff (#ffdab9)
    • peru (#cd853f)
    • pink (#ffc0cb)
    • plum (#dda0dd)
    • powderblue (#b0e0e6)
    • purple (#800080)
    • rebeccapurple (#663399)
    • red (#ff0000)
    • rosybrown (#bc8f8f)
    • royalblue (#4169e1)
    • saddlebrown (#8b4513)
    • salmon (#fa8072)
    • sandybrown (#f4a460)
    • seagreen (#2e8b57)
    • seashell (#fff5ee)
    • sienna (#a0522d)
    • silver (#c0c0c0)
    • skyblue (#87ceeb)
    • slateblue (#6a5acd)
    • slategray (#708090)
    • slategrey (#708090)
    • snow (#fffafa)
    • springgreen (#00ff7f)
    • steelblue (#4682b4)
    • tan (#d2b48c)
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    Communication between native and React Native #

    		Edit on GitHub

    In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.

    Introduction #

    React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If we have an ancestor component that rely on the state of its descendant, the recommended solution would be to pass down a callback that would be used by the descendant to update the ancestor.

    The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.

    Properties #

    Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.

    Passing properties from native to React Native #

    In order to embed a React Native view in a native component, we use RCTRootView. RCTRootView is a UIView that holds a React Native app. It also provides an interface between native side and the hosted app.

    RCTRootView has an initializer that allows you to pass arbitrary properties down to the React Native app. The initialProperties parameter has to be an instance of NSDictionary. The dictionary is internally converted into a JSON object that the top-level JS component can reference.

    NSArray *imageList = @[@"http://foo.com/bar1.png", +Communication between native and React Native – React Native | A framework for building native apps using React
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    Communication between native and React Native #

    		Edit on GitHub

    In Integrating with Existing Apps guide and Native UI Components guide we learn how to embed React Native in a native component and vice versa. When we mix native and React Native components, we'll eventually find a need to communicate between these two worlds. Some ways to achieve that have been already mentioned in other guides. This article summarizes available techniques.

    Introduction #

    React Native is inspired by React, so the basic idea of the information flow is similar. The flow in React is one-directional. We maintain a hierarchy of components, in which each component depends only on its parent and own internal state. We do this with properties: data is passed from a parent to its children in a top-down manner. If we have an ancestor component that rely on the state of its descendant, the recommended solution would be to pass down a callback that would be used by the descendant to update the ancestor.

    The same concept applies to React Native. As long as we are building our application purely within the framework, we can drive our app with properties and callbacks. But, when we mix React Native and native components, we need some special, cross-language mechanisms that would allow us to pass information between them.

    Properties #

    Properties are the simplest way of cross-component communication. So we need a way to pass properties both from native to React Native, and from React Native to native.

    Passing properties from native to React Native #

    In order to embed a React Native view in a native component, we use RCTRootView. RCTRootView is a UIView that holds a React Native app. It also provides an interface between native side and the hosted app.

    RCTRootView has an initializer that allows you to pass arbitrary properties down to the React Native app. The initialProperties parameter has to be an instance of NSDictionary. The dictionary is internally converted into a JSON object that the top-level JS component can reference.

    NSArray *imageList = @[@"http://foo.com/bar1.png", @"http://foo.com/bar2.png"]; NSDictionary *props = @{@"images" : imageList}; diff --git a/releases/next/docs/datepickerandroid.html b/releases/next/docs/datepickerandroid.html index b505f31fd6d..350234c9a2f 100644 --- a/releases/next/docs/datepickerandroid.html +++ b/releases/next/docs/datepickerandroid.html @@ -1,4 +1,4 @@ -DatePickerAndroid – React Native | A framework for building native apps using React
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    DatePickerAndroid #

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    Opens the standard Android date picker dialog.

    Example #

    try { +DatePickerAndroid – React Native | A framework for building native apps using React
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    DatePickerAndroid #

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    Opens the standard Android date picker dialog.

    Example #

    try { const {action, year, month, day} = await DatePickerAndroid.open({ // Use `new Date()` for current date. // May 25 2020. Month 0 is January. diff --git a/releases/next/docs/datepickerios.html b/releases/next/docs/datepickerios.html index beba416e788..8d76815940b 100644 --- a/releases/next/docs/datepickerios.html +++ b/releases/next/docs/datepickerios.html @@ -1,4 +1,4 @@ -DatePickerIOS – React Native | A framework for building native apps using React
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    DatePickerIOS #

    		Edit on GitHub

    Use DatePickerIOS to render a date/time picker (selector) on iOS. This is +DatePickerIOS – React Native | A framework for building native apps using React

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    DatePickerIOS #

    		Edit on GitHub

    Use DatePickerIOS to render a date/time picker (selector) on iOS. This is a controlled component, so you must hook in to the onDateChange callback and update the date prop in order for the component to update, otherwise the user's change will be reverted immediately to reflect props.date as the diff --git a/releases/next/docs/debugging.html b/releases/next/docs/debugging.html index fdf2b61f567..f9a44414f53 100644 --- a/releases/next/docs/debugging.html +++ b/releases/next/docs/debugging.html @@ -1,4 +1,4 @@ -Debugging – React Native | A framework for building native apps using React

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    Debugging #

    		Edit on GitHub

    Accessing the In-App Developer Menu #

    You can access the developer menu by shaking your device or by selecting "Shake Gesture" inside the Hardware menu in the iOS Simulator. You can also use the Command⌘ + D keyboard shortcut when your app is running in the iPhone Simulator, or Command⌘ + M when running in an Android emulator.

    The Developer Menu is disabled in release (production) builds.

    Reloading JavaScript #

    Instead of recompiling your app every time you make a change, you can reload your app's JavaScript code instantly. To do so, select "Reload" from the Developer Menu. You can also press Command⌘ + R in the iOS Simulator, or press R twice on Android emulators.

    If the Command⌘ + R keyboard shortcut does not seem to reload the iOS Simulator, go to the Hardware menu, select Keyboard, and make sure that "Connect Hardware Keyboard" is checked.

    Automatic reloading #

    You can speed up your development times by having your app reload automatically any time your code changes. Automatic reloading can be enabled by selecting "Enable Live Reload" from the Developer Menu.

    You may even go a step further and keep your app running as new versions of your files are injected into the JavaScript bundle automatically by enabling Hot Reloading from the Developer Menu. This will allow you to persist the app's state through reloads.

    There are some instances where hot reloading cannot be implemented perfectly. If you run into any issues, use a full reload to reset your app.

    You will need to rebuild your app for changes to take effect in certain situations:

    • You have added new resources to your native app's bundle, such as an image in Images.xcassets on iOS or the res/drawable folder on Android.
    • You have modified native code (Objective-C/Swift on iOS or Java/C++ on Android).

    In-app Errors and Warnings #

    Errors and warnings are displayed inside your app in development builds.

    Errors #

    In-app errors are displayed in a full screen alert with a red background inside your app. This screen is known as a RedBox. You can use console.error() to manually trigger one.

    Warnings #

    Warnings will be displayed on screen with a yellow background. These alerts are known as YellowBoxes. Click on the alerts to show more information or to dismiss them.

    As with a RedBox, you can use console.warn() to trigger a YellowBox.

    YellowBoxes can be disabled during development by using console.disableYellowBox = true;. Specific warnings can be ignored programmatically by setting an array of prefixes that should be ignored: console.ignoredYellowBox = ['Warning: ...'];

    RedBoxes and YellowBoxes are automatically disabled in release (production) builds.

    Accessing console logs #

    You can display the console logs for an iOS or Android app by using the following commands in a terminal while the app is running:

    $ react-native log-ios +Debugging – React Native | A framework for building native apps using React
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    Debugging #

    		Edit on GitHub

    Accessing the In-App Developer Menu #

    You can access the developer menu by shaking your device or by selecting "Shake Gesture" inside the Hardware menu in the iOS Simulator. You can also use the Command⌘ + D keyboard shortcut when your app is running in the iPhone Simulator, or Command⌘ + M when running in an Android emulator.

    The Developer Menu is disabled in release (production) builds.

    Reloading JavaScript #

    Instead of recompiling your app every time you make a change, you can reload your app's JavaScript code instantly. To do so, select "Reload" from the Developer Menu. You can also press Command⌘ + R in the iOS Simulator, or press R twice on Android emulators.

    If the Command⌘ + R keyboard shortcut does not seem to reload the iOS Simulator, go to the Hardware menu, select Keyboard, and make sure that "Connect Hardware Keyboard" is checked.

    Automatic reloading #

    You can speed up your development times by having your app reload automatically any time your code changes. Automatic reloading can be enabled by selecting "Enable Live Reload" from the Developer Menu.

    You may even go a step further and keep your app running as new versions of your files are injected into the JavaScript bundle automatically by enabling Hot Reloading from the Developer Menu. This will allow you to persist the app's state through reloads.

    There are some instances where hot reloading cannot be implemented perfectly. If you run into any issues, use a full reload to reset your app.

    You will need to rebuild your app for changes to take effect in certain situations:

    • You have added new resources to your native app's bundle, such as an image in Images.xcassets on iOS or the res/drawable folder on Android.
    • You have modified native code (Objective-C/Swift on iOS or Java/C++ on Android).

    In-app Errors and Warnings #

    Errors and warnings are displayed inside your app in development builds.

    Errors #

    In-app errors are displayed in a full screen alert with a red background inside your app. This screen is known as a RedBox. You can use console.error() to manually trigger one.

    Warnings #

    Warnings will be displayed on screen with a yellow background. These alerts are known as YellowBoxes. Click on the alerts to show more information or to dismiss them.

    As with a RedBox, you can use console.warn() to trigger a YellowBox.

    YellowBoxes can be disabled during development by using console.disableYellowBox = true;. Specific warnings can be ignored programmatically by setting an array of prefixes that should be ignored: console.ignoredYellowBox = ['Warning: ...'];

    RedBoxes and YellowBoxes are automatically disabled in release (production) builds.

    Accessing console logs #

    You can display the console logs for an iOS or Android app by using the following commands in a terminal while the app is running:

    $ react-native log-ios $ react-native log-android

    You may also access these through Debug → Open System Log... in the iOS Simulator or by running adb logcat *:S ReactNative:V ReactNativeJS:V in a terminal while an Android app is running on a device or emulator.

    Chrome Developer Tools #

    To debug the JavaScript code in Chrome, select "Debug JS Remotely" from the Developer Menu. This will open a new tab at http://localhost:8081/debugger-ui.

    Select Tools → Developer Tools from the Chrome Menu to open the Developer Tools. You may also access the DevTools using keyboard shortcuts (Command⌘ + Option⌥ + I on Mac, Ctrl + Shift + I on Windows). You may also want to enable Pause On Caught Exceptions for a better debugging experience.

    It is currently not possible to use the "React" tab in the Chrome Developer Tools to inspect app widgets. You can use Nuclide's "React Native Inspector" as a workaround.

    Debugging on a device with Chrome Developer Tools #

    On iOS devices, open the file RCTWebSocketExecutor.m and change "localhost" to the IP address of your computer, then select "Debug JS Remotely" from the Developer Menu.

    On Android 5.0+ devices connected via USB, you can use the adb command line tool to setup port forwarding from the device to your computer:

    adb reverse tcp:8081 tcp:8081

    Alternatively, select "Dev Settings" from the Developer Menu, then update the "Debug server host for device" setting to match the IP address of your computer.

    If you run into any issues, it may be possible that one of your Chrome extensions is interacting in unexpected ways with the debugger. Try disabling all of your extensions and re-enabling them one-by-one until you find the problematic extension.

    Debugging using a custom JavaScript debugger #

    To use a custom JavaScript debugger in place of Chrome Developer Tools, set the REACT_DEBUGGER environment variable to a command that will start your custom debugger. You can then select "Debug JS Remotely" from the Developer Menu to start debugging.

    The debugger will receive a list of all project roots, separated by a space. For example, if you set REACT_DEBUGGER="node /path/to/launchDebugger.js --port 2345 --type ReactNative", then the command node /path/to/launchDebugger.js --port 2345 --type ReactNative /path/to/reactNative/app will be used to start your debugger.

    Custom debugger commands executed this way should be short-lived processes, and they shouldn't produce more than 200 kilobytes of output.

    Performance Monitor #

    You can enable a performance overlay to help you debug performance problems by selecting "Perf Monitor" in the Developer Menu.

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    Dimensions #

    		Edit on GitHub

    Methods #

    static set(dims) #

    This should only be called from native code by sending the +Dimensions – React Native | A framework for building native apps using React

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    Dimensions #

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    Methods #

    static set(dims) #

    This should only be called from native code by sending the didUpdateDimensions event.

    @param {object} dims Simple string-keyed object of dimensions to set

    static get(dim) #

    Initial dimensions are set before runApplication is called so they should be available before any other require's are run, but may be updated later.

    Note: Although dimensions are available immediately, they may change (e.g due to device rotation) so any rendering logic or styles that depend on diff --git a/releases/next/docs/direct-manipulation.html b/releases/next/docs/direct-manipulation.html index b7a035b6fa8..c2eaa5b501e 100644 --- a/releases/next/docs/direct-manipulation.html +++ b/releases/next/docs/direct-manipulation.html @@ -1,4 +1,4 @@ -Direct Manipulation – React Native | A framework for building native apps using React

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    Direct Manipulation #

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    It is sometimes necessary to make changes directly to a component +Direct Manipulation – React Native | A framework for building native apps using React

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    Direct Manipulation #

    		Edit on GitHub

    It is sometimes necessary to make changes directly to a component without using state/props to trigger a re-render of the entire subtree. When using React in the browser for example, you sometimes need to directly modify a DOM node, and the same is true for views in mobile diff --git a/releases/next/docs/drawerlayoutandroid.html b/releases/next/docs/drawerlayoutandroid.html index 26d19f18d1c..3dba5845872 100644 --- a/releases/next/docs/drawerlayoutandroid.html +++ b/releases/next/docs/drawerlayoutandroid.html @@ -1,4 +1,4 @@ -DrawerLayoutAndroid – React Native | A framework for building native apps using React

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    DrawerLayoutAndroid #

    		Edit on GitHub

    React component that wraps the platform DrawerLayout (Android only). The +DrawerLayoutAndroid – React Native | A framework for building native apps using React

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    DrawerLayoutAndroid #

    		Edit on GitHub

    React component that wraps the platform DrawerLayout (Android only). The Drawer (typically used for navigation) is rendered with renderNavigationView and direct children are the main view (where your content goes). The navigation view is initially not visible on the screen, but can be pulled in from the diff --git a/releases/next/docs/flexbox.html b/releases/next/docs/flexbox.html index 6cca5b229af..707d9fe4bde 100644 --- a/releases/next/docs/flexbox.html +++ b/releases/next/docs/flexbox.html @@ -1,4 +1,4 @@ -Layout with Flexbox – React Native | A framework for building native apps using React

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    Layout with Flexbox #

    		Edit on GitHub

    A component can specify the layout of its children using the flexbox algorithm. Flexbox is designed to provide a consistent layout on different screen sizes.

    You will normally use a combination of flexDirection, alignItems, and justifyContent to achieve the right layout.

    Flexbox works the same way in React Native as it does in CSS on the web, with a few exceptions. The defaults are different, with flexDirection defaulting to column instead of row, and alignItems defaulting to stretch instead of flex-start, and the flex parameter only supports a single number.

    Flex Direction #

    Adding flexDirection to a component's style determines the primary axis of its layout. Should the children be organized horizontally (row) or vertically (column)? The default is column.

    import React, { Component } from 'react'; +Layout with Flexbox – React Native | A framework for building native apps using React
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    Layout with Flexbox #

    		Edit on GitHub

    A component can specify the layout of its children using the flexbox algorithm. Flexbox is designed to provide a consistent layout on different screen sizes.

    You will normally use a combination of flexDirection, alignItems, and justifyContent to achieve the right layout.

    Flexbox works the same way in React Native as it does in CSS on the web, with a few exceptions. The defaults are different, with flexDirection defaulting to column instead of row, and alignItems defaulting to stretch instead of flex-start, and the flex parameter only supports a single number.

    Flex Direction #

    Adding flexDirection to a component's style determines the primary axis of its layout. Should the children be organized horizontally (row) or vertically (column)? The default is column.

    import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class FlexDirectionBasics extends Component { diff --git a/releases/next/docs/geolocation.html b/releases/next/docs/geolocation.html index 3fa08057534..52cd700f48d 100644 --- a/releases/next/docs/geolocation.html +++ b/releases/next/docs/geolocation.html @@ -1,4 +1,4 @@ -Geolocation – React Native | A framework for building native apps using React
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    Geolocation #

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    The Geolocation API follows the web spec: +Geolocation – React Native | A framework for building native apps using React

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    Geolocation #

    		Edit on GitHub

    The Geolocation API follows the web spec: https://developer.mozilla.org/en-US/docs/Web/API/Geolocation

    iOS #

    You need to include the NSLocationWhenInUseUsageDescription key in Info.plist to enable geolocation. Geolocation is enabled by default when you create a project with react-native init.

    Android #

    To request access to location, you need to add the following line to your diff --git a/releases/next/docs/gesture-responder-system.html b/releases/next/docs/gesture-responder-system.html index cde99735f2a..b741dcd05bd 100644 --- a/releases/next/docs/gesture-responder-system.html +++ b/releases/next/docs/gesture-responder-system.html @@ -1,4 +1,4 @@ -Gesture Responder System – React Native | A framework for building native apps using React

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    Gesture Responder System #

    		Edit on GitHub

    Gesture recognition on mobile devices is much more complicated than web. A touch can go through several phases as the app determines what the user's intention is. For example, the app needs to determine if the touch is scrolling, sliding on a widget, or tapping. This can even change during the duration of a touch. There can also be multiple simultaneous touches.

    The touch responder system is needed to allow components to negotiate these touch interactions without any additional knowledge about their parent or child components. This system is implemented in ResponderEventPlugin.js, which contains further details and documentation.

    Best Practices #

    Users can feel huge differences in the usability of web apps vs. native, and this is one of the big causes. Every action should have the following attributes:

    • Feedback/highlighting- show the user what is handling their touch, and what will happen when they release the gesture
    • Cancel-ability- when making an action, the user should be able to abort it mid-touch by dragging their finger away

    These features make users more comfortable while using an app, because it allows people to experiment and interact without fear of making mistakes.

    TouchableHighlight and Touchable* #

    The responder system can be complicated to use. So we have provided an abstract Touchable implementation for things that should be "tappable". This uses the responder system and allows you to easily configure tap interactions declaratively. Use TouchableHighlight anywhere where you would use a button or link on web.

    Responder Lifecycle #

    A view can become the touch responder by implementing the correct negotiation methods. There are two methods to ask the view if it wants to become responder:

    • View.props.onStartShouldSetResponder: (evt) => true, - Does this view want to become responder on the start of a touch?
    • View.props.onMoveShouldSetResponder: (evt) => true, - Called for every touch move on the View when it is not the responder: does this view want to "claim" touch responsiveness?

    If the View returns true and attempts to become the responder, one of the following will happen:

    • View.props.onResponderGrant: (evt) => {} - The View is now responding for touch events. This is the time to highlight and show the user what is happening
    • View.props.onResponderReject: (evt) => {} - Something else is the responder right now and will not release it

    If the view is responding, the following handlers can be called:

    • View.props.onResponderMove: (evt) => {} - The user is moving their finger
    • View.props.onResponderRelease: (evt) => {} - Fired at the end of the touch, ie "touchUp"
    • View.props.onResponderTerminationRequest: (evt) => true - Something else wants to become responder. Should this view release the responder? Returning true allows release
    • View.props.onResponderTerminate: (evt) => {} - The responder has been taken from the View. Might be taken by other views after a call to onResponderTerminationRequest, or might be taken by the OS without asking (happens with control center/ notification center on iOS)

    evt is a synthetic touch event with the following form:

    • nativeEvent
      • changedTouches - Array of all touch events that have changed since the last event
      • identifier - The ID of the touch
      • locationX - The X position of the touch, relative to the element
      • locationY - The Y position of the touch, relative to the element
      • pageX - The X position of the touch, relative to the root element
      • pageY - The Y position of the touch, relative to the root element
      • target - The node id of the element receiving the touch event
      • timestamp - A time identifier for the touch, useful for velocity calculation
      • touches - Array of all current touches on the screen

    Capture ShouldSet Handlers #

    onStartShouldSetResponder and onMoveShouldSetResponder are called with a bubbling pattern, where the deepest node is called first. That means that the deepest component will become responder when multiple Views return true for *ShouldSetResponder handlers. This is desirable in most cases, because it makes sure all controls and buttons are usable.

    However, sometimes a parent will want to make sure that it becomes responder. This can be handled by using the capture phase. Before the responder system bubbles up from the deepest component, it will do a capture phase, firing on*ShouldSetResponderCapture. So if a parent View wants to prevent the child from becoming responder on a touch start, it should have a onStartShouldSetResponderCapture handler which returns true.

    • View.props.onStartShouldSetResponderCapture: (evt) => true,
    • View.props.onMoveShouldSetResponderCapture: (evt) => true,

    PanResponder #

    For higher-level gesture interpretation, check out PanResponder.

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    Gesture Responder System #

    		Edit on GitHub

    Gesture recognition on mobile devices is much more complicated than web. A touch can go through several phases as the app determines what the user's intention is. For example, the app needs to determine if the touch is scrolling, sliding on a widget, or tapping. This can even change during the duration of a touch. There can also be multiple simultaneous touches.

    The touch responder system is needed to allow components to negotiate these touch interactions without any additional knowledge about their parent or child components. This system is implemented in ResponderEventPlugin.js, which contains further details and documentation.

    Best Practices #

    Users can feel huge differences in the usability of web apps vs. native, and this is one of the big causes. Every action should have the following attributes:

    • Feedback/highlighting- show the user what is handling their touch, and what will happen when they release the gesture
    • Cancel-ability- when making an action, the user should be able to abort it mid-touch by dragging their finger away

    These features make users more comfortable while using an app, because it allows people to experiment and interact without fear of making mistakes.

    TouchableHighlight and Touchable* #

    The responder system can be complicated to use. So we have provided an abstract Touchable implementation for things that should be "tappable". This uses the responder system and allows you to easily configure tap interactions declaratively. Use TouchableHighlight anywhere where you would use a button or link on web.

    Responder Lifecycle #

    A view can become the touch responder by implementing the correct negotiation methods. There are two methods to ask the view if it wants to become responder:

    • View.props.onStartShouldSetResponder: (evt) => true, - Does this view want to become responder on the start of a touch?
    • View.props.onMoveShouldSetResponder: (evt) => true, - Called for every touch move on the View when it is not the responder: does this view want to "claim" touch responsiveness?

    If the View returns true and attempts to become the responder, one of the following will happen:

    • View.props.onResponderGrant: (evt) => {} - The View is now responding for touch events. This is the time to highlight and show the user what is happening
    • View.props.onResponderReject: (evt) => {} - Something else is the responder right now and will not release it

    If the view is responding, the following handlers can be called:

    • View.props.onResponderMove: (evt) => {} - The user is moving their finger
    • View.props.onResponderRelease: (evt) => {} - Fired at the end of the touch, ie "touchUp"
    • View.props.onResponderTerminationRequest: (evt) => true - Something else wants to become responder. Should this view release the responder? Returning true allows release
    • View.props.onResponderTerminate: (evt) => {} - The responder has been taken from the View. Might be taken by other views after a call to onResponderTerminationRequest, or might be taken by the OS without asking (happens with control center/ notification center on iOS)

    evt is a synthetic touch event with the following form:

    • nativeEvent
      • changedTouches - Array of all touch events that have changed since the last event
      • identifier - The ID of the touch
      • locationX - The X position of the touch, relative to the element
      • locationY - The Y position of the touch, relative to the element
      • pageX - The X position of the touch, relative to the root element
      • pageY - The Y position of the touch, relative to the root element
      • target - The node id of the element receiving the touch event
      • timestamp - A time identifier for the touch, useful for velocity calculation
      • touches - Array of all current touches on the screen

    Capture ShouldSet Handlers #

    onStartShouldSetResponder and onMoveShouldSetResponder are called with a bubbling pattern, where the deepest node is called first. That means that the deepest component will become responder when multiple Views return true for *ShouldSetResponder handlers. This is desirable in most cases, because it makes sure all controls and buttons are usable.

    However, sometimes a parent will want to make sure that it becomes responder. This can be handled by using the capture phase. Before the responder system bubbles up from the deepest component, it will do a capture phase, firing on*ShouldSetResponderCapture. So if a parent View wants to prevent the child from becoming responder on a touch start, it should have a onStartShouldSetResponderCapture handler which returns true.

    • View.props.onStartShouldSetResponderCapture: (evt) => true,
    • View.props.onMoveShouldSetResponderCapture: (evt) => true,

    PanResponder #

    For higher-level gesture interpretation, check out PanResponder.

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    Getting Started #

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    Welcome to React Native! This page will help you install React Native on +Getting Started – React Native | A framework for building native apps using React

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    Getting Started #

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    Welcome to React Native! This page will help you install React Native on your system, so that you can build apps with it right away. If you already have React Native installed, you can skip ahead to the Tutorial.

    The instructions are a bit different depending on your development operating system, and whether you want to start developing for iOS or Android. If you diff --git a/releases/next/docs/handling-text-input.html b/releases/next/docs/handling-text-input.html index 06a43fa0f48..cf05b878d5c 100644 --- a/releases/next/docs/handling-text-input.html +++ b/releases/next/docs/handling-text-input.html @@ -1,4 +1,4 @@ -Handling Text Input – React Native | A framework for building native apps using React

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    Handling Text Input #

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    TextInput is a basic component that allows the user to enter text. It has an onChangeText prop that takes +Handling Text Input – React Native | A framework for building native apps using React

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    Handling Text Input #

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    TextInput is a basic component that allows the user to enter text. It has an onChangeText prop that takes a function to be called every time the text changed, and an onSubmitEditing prop that takes a function to be called when the text is submitted.

    For example, let's say that as the user types, you're translating their words into a different language. In this new language, every single word is written the same way: 🍕. So the sentence "Hello there Bob" would be translated as "🍕🍕🍕".

    import React, { Component } from 'react'; import { AppRegistry, Text, TextInput, View } from 'react-native'; diff --git a/releases/next/docs/handling-touches.html b/releases/next/docs/handling-touches.html index 7cc279537a4..62a5421663d 100644 --- a/releases/next/docs/handling-touches.html +++ b/releases/next/docs/handling-touches.html @@ -1,4 +1,4 @@ -Handling Touches – React Native | A framework for building native apps using React
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    Handling Touches #

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    Users interact with mobile apps mainly through touch. They can use a combination of gestures, such as tapping on a button, scrolling a list, or zooming on a map.

    React Native provides components to handle common gestures, such as taps and swipes, as well as a comprehensive gesture responder system to allow for more advanced gesture recognition.

    Tappable Components #

    You can use "Touchable" components when you want to capture a tapping gesture. They take a function through the onPress props which will be called when the touch begins and ends within the bounds of the component.

    Example:

    class MyButton extends Component { +Handling Touches – React Native | A framework for building native apps using React
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    Handling Touches #

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    Users interact with mobile apps mainly through touch. They can use a combination of gestures, such as tapping on a button, scrolling a list, or zooming on a map.

    React Native provides components to handle common gestures, such as taps and swipes, as well as a comprehensive gesture responder system to allow for more advanced gesture recognition.

    Tappable Components #

    You can use "Touchable" components when you want to capture a tapping gesture. They take a function through the onPress props which will be called when the touch begins and ends within the bounds of the component.

    Example:

    class MyButton extends Component { _onPressButton() { console.log("You tapped the button!"); } diff --git a/releases/next/docs/height-and-width.html b/releases/next/docs/height-and-width.html index 37c325a0830..634c8e71e8d 100644 --- a/releases/next/docs/height-and-width.html +++ b/releases/next/docs/height-and-width.html @@ -1,4 +1,4 @@ -Height and Width – React Native | A framework for building native apps using React
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    Height and Width #

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    A component's height and width determine its size on the screen.

    Fixed Dimensions #

    The simplest way to set the dimensions of a component is by adding a fixed width and height to style. All dimensions in React Native are unitless, and represent density-independent pixels.

    import React, { Component } from 'react'; +Height and Width – React Native | A framework for building native apps using React
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    Height and Width #

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    A component's height and width determine its size on the screen.

    Fixed Dimensions #

    The simplest way to set the dimensions of a component is by adding a fixed width and height to style. All dimensions in React Native are unitless, and represent density-independent pixels.

    import React, { Component } from 'react'; import { AppRegistry, View } from 'react-native'; class FixedDimensionsBasics extends Component { diff --git a/releases/next/docs/image.html b/releases/next/docs/image.html index 98eef4c89a8..ca015120d63 100644 --- a/releases/next/docs/image.html +++ b/releases/next/docs/image.html @@ -1,4 +1,4 @@ -Image – React Native | A framework for building native apps using React
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    Image #

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    A React component for displaying different types of images, +Image – React Native | A framework for building native apps using React

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    Image #

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    A React component for displaying different types of images, including network images, static resources, temporary local images, and images from local disk, such as the camera roll.

    This exmaples shows both fetching and displaying an image from local storage as well as on from network.

    import React, { Component } from 'react'; diff --git a/releases/next/docs/images.html b/releases/next/docs/images.html index cf38cd9cad7..4757472f6c9 100644 --- a/releases/next/docs/images.html +++ b/releases/next/docs/images.html @@ -1,4 +1,4 @@ -Images – React Native | A framework for building native apps using React
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    Images #

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    Static Image Resources #

    As of 0.14 release, React Native provides a unified way of managing images in your iOS and Android apps. To add a static image to your app, place it somewhere in your source code tree and reference it like this:

    <Image source={require('./my-icon.png')} />

    The image name is resolved the same way JS modules are resolved. In the example above the packager will look for my-icon.png in the same folder as the component that requires it. Also if you have my-icon.ios.png and my-icon.android.png, the packager will pick the file depending on the platform you are running on.

    You can also use @2x, @3x, etc. suffix in the file name to provide images for different screen densities. For example, if you have the following file structure:

    . +Images – React Native | A framework for building native apps using React
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    Images #

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    Static Image Resources #

    As of 0.14 release, React Native provides a unified way of managing images in your iOS and Android apps. To add a static image to your app, place it somewhere in your source code tree and reference it like this:

    <Image source={require('./my-icon.png')} />

    The image name is resolved the same way JS modules are resolved. In the example above the packager will look for my-icon.png in the same folder as the component that requires it. Also if you have my-icon.ios.png and my-icon.android.png, the packager will pick the file depending on the platform you are running on.

    You can also use @2x, @3x, etc. suffix in the file name to provide images for different screen densities. For example, if you have the following file structure:

    . ├── button.js └── img ├── check@2x.png diff --git a/releases/next/docs/integration-with-existing-apps.html b/releases/next/docs/integration-with-existing-apps.html index 5eaa094fdd1..098efb835f3 100644 --- a/releases/next/docs/integration-with-existing-apps.html +++ b/releases/next/docs/integration-with-existing-apps.html @@ -1,4 +1,4 @@ -Integration With Existing Apps – React Native | A framework for building native apps using React
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    Integration With Existing Apps #

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    Integration With Existing Apps #

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