Spencer Ahrens
8ddf231306
Summary: Fixes https://github.com/facebook/react-native/issues/16067 The issue is due to a race between `onLayout` and `onContentSizeChange`, which in general should be fine because there is no expectation of ordering between the two, and only causes issues with certain configurations. The bug can be triggered if `initialNumToRender` is smaller than needed to fill past the `onEndReachedThreshold` (say the default, 10, is only 580px tall, but it takes 15 to reach the threshold). This will cause an incrementally render of more items to try and fill the viewport. The problem is that if the `onLayout` comes back before the first `onContentSizeChange`, it will first do the state increment to render 20 items and then the stale `onContentSizeChange` callback from 10 items will fire and we'll think that the content size for 20 items is 580px when in fact it's 1160px (which is past the threshold). If those 20 items are also all of our available data, then we'll call `onEndReached` because we think we've rendered everything and are still within the `onEndReachedThreshold`. The fundamental problem here is the system getting confused when a stale async `onContentSizeChange` comes in after increasing `state.last`. I wish there was a concrete timeframe, but Fabric will give us more flexibility to do things synchronously so hopefully we can avoid class of issues once that roles out. The fix here simply adds a check to make sure `contentLength` has been set before adjusting the render window so it's not possible to increase the window size before the initial `onContentSizeChange` callback fires. For completeness, there are a few user-code workarounds to avoid this issue entirely: 1) Provide the `getItemLayout` prop so the list doesn't have to rely on async layout data (you should do this whenever possible anyway for better perf). e.g. for the original snack example, you can just add `getItemLayout={(d, index) => ({length: 58, offset: 58 * index, index})}` since all the rows are height 58 and the issue will no longer repro. Note this is fragile and must be kept in sync with UI changes, a11y font scaling, etc - a more robust approach could be to render a single representative row offscreen and measure it with `onLayout` then use that value. 2) If `getItemLayout` is not feasible to compute for your UI, increase `initialNumToRender` to cover the `onEndReachedThreshold`. 3) And/or add your own logic to protect against extra calls to `onEndReached` as others have suggested. Changelog: [General][Fixed] - Fix sporadic issue with onEndReached called on load when not needed # Test Plan Adds a new jest test that fails without this fix and succeeds with it. Reviewed By: TheSavior Differential Revision: D18966721 fbshipit-source-id: de05d9f072e24a2faf351e7f5d60578a31def996
React Native
Learn once, write anywhere:
Build mobile apps with React.
Getting Started · Learn the Basics · Showcase · Contribute · Community · Support
React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 9.0 and Android 4.1 (API 16) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
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 full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools, and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in the React Native Community, @react-native-community/react-native-releases.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.