d8fcdb9bd7
Summary: Fixes issue #11828 that causes layout animations for removed views to remove some adjacent views as well. This happens because the animated views are still present in the ViewGroup, which throws off subsequent operations that rely on view indices having updated. This issue was addressed in #11962, which was closed in favour of a more reliable solution that addresses the issue globally since it’s difficult to account for animated views everywhere. janicduplessis [recommended][0] handling the issue through ViewManager. Since API 11, Android provides `ViewGroup#startViewTransition(View)` that can be used to keep child views visible even if they have been removed from the group. ViewGroup keeps an array of these views, which is only used for drawing. Methods such as `ViewGroup#getChildCount()` and `ViewGroup#getChildAt(int)` will ignore them. I believe relying on these framework methods within ViewManager is the most reliable way to solve this issue because it also works if callers ignore ViewManager and reach into the native view indices and counts directly. [0]: https://github.com/facebook/react-native/pull/11962#pullrequestreview-21862640 I wrote a minimal test app that you can find here: <https://gist.github.com/lnikkila/87f3825442a5773f17ead433a810d53f> The expected result is that the red and green squares disappear, a blue one appears, and the black one stays in place. iOS has this behaviour, but Android removes the black square as well. We can see the bug with some breakpoint logging. Without LayoutAnimation: ``` NativeViewHierarchyOptimizer: Removing node from parent with tag 2 at index 0 NativeViewHierarchyOptimizer: Removing node from parent with tag 4 at index 1 NativeViewHierarchyManager: Removing indices [0] with tags [2] RootViewManager: Removing child view at index 0 with tag 2 NativeViewHierarchyManager: Removing indices [1] with tags [4] RootViewManager: Removing child view at index 1 with tag 4 ``` With LayoutAnimation tag 3 gets removed when it shouldn’t be: ``` NativeViewHierarchyOptimizer: Removing node from parent with tag 2 at index 0 NativeViewHierarchyOptimizer: Removing node from parent with tag 4 at index 1 NativeViewHierarchyManager: Removing indices [0] with tags [2] NativeViewHierarchyManager: Removing indices [1] with tags [4] -> RootViewManager: Removing child view at index 1 with tag 3 RootViewManager: Removing child view at index 2 with tag 4 (Animation listener kicks in here) RootViewManager: Removing child view at index 1 with tag 2 ``` Here are some GIFs to compare, click to expand: <details> <summary><b>Current master (iOS vs Android)</b></summary> <p></p> <img src="https://user-images.githubusercontent.com/1291143/38695083-fbc29cd4-3e93-11e8-9150-9b8ea75b87aa.gif" height="400" /><img src="https://user-images.githubusercontent.com/1291143/38695108-06eb73a6-3e94-11e8-867a-b95d7f926ccd.gif" height="400" /> </details><p></p> <details> <summary><b>With this patch (iOS vs Android, fixed)</b></summary> <p></p> <img src="https://user-images.githubusercontent.com/1291143/38695083-fbc29cd4-3e93-11e8-9150-9b8ea75b87aa.gif" height="400" /><img src="https://user-images.githubusercontent.com/1291143/38695137-1090f782-3e94-11e8-94c8-ce33a5d7ebdb.gif" height="400" /> </details><p></p> Previously addressed in #11962, which wasn’t merged. Tangentially related to my other LayoutAnimation PR #18651. No documentation changes needed. [ANDROID] [BUGFIX] [LayoutAnimation] - Removal LayoutAnimations no longer remove adjacent views as well in certain cases. Closes https://github.com/facebook/react-native/pull/18830 Reviewed By: achen1 Differential Revision: D7612904 Pulled By: mdvacca fbshipit-source-id: a04cf47ab80e0e813fa043125b1f907e212b1ad4
React Native · 
Learn once, write anywhere: Build mobile apps with React.
- Build native mobile apps using JavaScript and React: React Native lets you build mobile apps using only JavaScript. It uses the same design as React, letting you compose a rich mobile UI from declarative components.
- A React Native app is a real mobile app: With React Native, you don't build a "mobile web app", an "HTML5 app", or a "hybrid app". You build a real mobile app that's indistinguishable from an app built using Objective-C, Java, or Swift. React Native uses the same fundamental UI building blocks as regular iOS and Android apps. You just put those building blocks together using JavaScript and React.
- Don't waste time recompiling: React Native lets you build your app faster. Instead of recompiling, you can reload your app instantly. With hot reloading, you can even run new code while retaining your application state. Give it a try - it's a magical experience.
- Use native code when you need to: React Native combines smoothly with components written in Objective-C, Java, or Swift. It's simple to drop down to native code if you need to optimize a few aspects of your application. It's also easy to build part of your app in React Native, and part of your app using native code directly - that's how the Facebook app works.
The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
See the official React Native website for an introduction to React Native.
Supported operating systems are >= Android 4.1 (API 16) and >= iOS 8.0.
Getting Started
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
Documentation
The website’s documentation is divided into multiple sections.
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- The Components section covers React components such as
ViewandButton. - The APIs section covers other libraries like Animated and StyleSheet that aren’t React components themselves.
- Finally, React Native provides a small number of Polyfills that offer web-like APIs.
Another great way to learn more about the components and APIs included with React Native is to read their source. Look under the Libraries/Components directory for components like ScrollView and TextInput, for example. The RNTester example is also here to demonstrate some of the ways to use these components. From the source you can get an accurate understanding of each component’s behavior and API.
The React Native documentation only discusses the components, APIs and topics specific to React Native (React on iOS and Android). For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
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Beginner Friendly Bugs
We have a list of beginner friendly issues to help you get your feet wet in the React Native codebase and familiar with our contribution process. This is a great place to get started.
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React Native is MIT licensed.
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