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Summary: This diff implement the CSS z-index for React Native iOS views. We've had numerous pull request for this feature, but they've all attempted to use the `layer.zPosition` property, which is problematic for two reasons: 1. zPosition only affects rendering order, not event processing order. Views with a higher zPosition will appear in front of others in the hierarchy, but won't be the first to receive touch events, and may be blocked by views that are visually behind them. 2. when using a perspective transform matrix, views with a nonzero zPosition will be rendered in a different position due to parallax, which probably isn't desirable. See https://github.com/facebook/react-native/pull/7825 for further discussion of this problem. So instead of using `layer.zPosition`, I've implemented this by actually adjusting the order of the subviews within their parent based on the zIndex. This can't be done on the JS side because it would affect layout, which is order-dependent, so I'm doing it inside the view itself. It works as follows: 1. The `reactSubviews` array is set, whose order matches the order of the JS components and shadowView components, as specified by the UIManager. 2. `didUpdateReactSubviews` is called, which in turn calls `sortedSubviews` (which lazily generates a sorted array of `reactSubviews` by zIndex) and inserts the result into the view. 3. If a subview is added or removed, or the zIndex of any subview is changed, the previous `sortedSubviews` array is cleared and `didUpdateReactSubviews` is called again. To demonstrate it working, I've modified the UIExplorer example from https://github.com/facebook/react-native/pull/7825 Reviewed By: javache Differential Revision: D3365717 fbshipit-source-id: b34aa8bfad577bce023f8af5414f9b974aafd8aa
UIExplorer
The UIExplorer is a sample app that showcases React Native views and modules.
Running this app
Before running the app, make sure you ran:
git clone https://github.com/facebook/react-native.git
cd react-native
npm install
Running on iOS
Mac OS and Xcode are required.
- Open
Examples/UIExplorer/UIExplorer.xcodeprojin Xcode - Hit the Run button
See Running on device if you want to use a physical device.
Running on Android
You'll need to have all the prerequisites (SDK, NDK) for Building React Native installed.
Start an Android emulator (Genymotion is recommended).
cd react-native
./gradlew :Examples:UIExplorer:android:app:installDebug
./packager/packager.sh
Note: Building for the first time can take a while.
Open the UIExplorer app in your emulator.
See Running on Device in case you want to use a physical device.
Running with Buck
Follow the same setup as running with gradle.
Install Buck from here.
Run the following commands from the react-native folder:
./gradlew :ReactAndroid:packageReactNdkLibsForBuck
buck fetch uiexplorer
buck install -r uiexplorer
./packager/packager.sh
Note: The native libs are still built using gradle. Full build with buck is coming soon(tm).
Built from source
Building the app on both iOS and Android means building the React Native framework from source. This way you're running the latest native and JS code the way you see it in your clone of the github repo.
This is different from apps created using react-native init which have a dependency on a specific version of React Native JS and native code, declared in a package.json file (and build.gradle for Android apps).