8ea6cea39a
Summary: It's very important in complex UIs to be able to apply alpha channel-based masks to arbitrary content. Common use cases include adding gradient masks at the top or bottom of scroll views, creating masked text effects, feathering images, and generally just masking views while still allowing transparency of those views. The original motivation for creating this component stemmed from work on `react-navigation`. As I tried to mimic behavior in the native iOS header, I needed to be able to achieve the effect pictured here (this is a screenshot from a native iOS application):  In this image, there are two masks: - A mask on the back button chevron - A gradient mask on the right button In addition, the underlying view in the navigation bar is intended to be a UIBlurView. Thus, alpha masking is the only way to achieve this effect. Behind the scenes, the `maskView` property on `UIView` is used. This is a shortcut to setting the mask on the CALayer directly. This gives us the ability to mask any view with any other view. While building this component (and testing in the context of an Expo app), I was able to use a `GLView` (a view that renders an OpenGL context) to mask a `Video` component! I chose to implement this only on iOS right now, as the Android implementation is a) significantly more complicated and b) will most likely not be as performant (especially when trying to mask more complex views). Review the `<MaskedViewIOS>` section in the RNTester app, observe that views are masked appropriately.  Closes https://github.com/facebook/react-native/pull/14898 Differential Revision: D5398721 Pulled By: javache fbshipit-source-id: 343af874e2d664541aca1fefe922cf7d82aea701
React Native 
React Native enables you to build world-class application experiences on native platforms using a consistent developer experience based on JavaScript and React. 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.
Supported operating systems are >= Android 4.1 (API 16) and >= iOS 8.0.
- Getting Started
- Getting Help
- Documentation
- Examples
- Extending React Native
- Upgrading
- Opening Issues
- Contributing
- License
Introduction
See the official React Native website for an introduction to React Native.
Getting Started
- Follow the Getting Started guide to install React Native and its dependencies.
- Open the RNTester app to see a list of components that ship with React Native.
- Install the React Developer Tools for Chrome or Firefox for better debugging (read more).
- Try out apps from the Showcase to see what React Native is capable of!
Getting Help
Please use these community resources for getting help. We use the GitHub issues for tracking bugs and feature requests and have limited bandwidth to address them.
- Ask a question on StackOverflow and tag it with
react-native - Chat with us on Reactiflux in #react-native
- Articulate your feature request or upvote existing ones on Canny
- Start a thread on the React Discussion Board
- Join #reactnative on IRC: chat.freenode.net
- If it turns out that you may have found a bug, please open an issue
Documentation
The website’s documentation is divided into multiple sections.
- There are Guides that discuss topics like debugging, integrating with existing apps, and the gesture responder system.
- 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.
Examples
git clone https://github.com/facebook/react-native.gitcd react-native && npm install
Running the RNTester app on iOS
Now open RNTester/RNTester.xcodeproj and hit Run in Xcode.
Running the RNTester app on Android
Note that you'll need the Android NDK installed, see prerequisites.
./gradlew :RNTester:android:app:installDebug
# Start the packager in a separate shell (make sure you ran npm install):
./scripts/packager.sh
Extending React Native
- Looking for a component? JS.coach
- Fellow developers write and publish React Native modules to npm and open source them on GitHub.
- Making modules helps grow the React Native ecosystem and community. We recommend writing modules for your use cases and sharing them on npm.
- Read the guides on Native Modules (iOS, Android) and Native UI Components (iOS, Android) if you are interested in extending native functionality.
Upgrading
React Native is under active development. See the guide on upgrading React Native to keep your project up-to-date.
Opening Issues
If you encounter a bug with React Native we would like to hear about it. Search the existing issues and try to make sure your problem doesn’t already exist before opening a new issue. It’s helpful if you include the version of React Native and OS you’re using. Please include a stack trace and reduced repro case when appropriate, too.
The GitHub issues are intended for bug reports and feature requests. For help and questions with using React Native please make use of the resources listed in the Getting Help section. Canny in particular is a good way to signal your interest in a feature or issue. There are limited resources available for handling issues and by keeping the list of open issues lean we can respond in a timely manner.
Contributing
For more information about contributing PRs and issues, see our Contribution Guidelines.
Good First Task is a great starting point for PRs.
We encourage the community to ask and answer questions on Stack Overflow with the react-native tag. It's a great way to help out and be involved!
License
React is BSD licensed. We also provide an additional patent grant.
React documentation is Creative Commons licensed.
Examples provided in this repository and in the documentation are separately licensed, as are some of the custom components.