离线支持
你的应用可能会遇到网络连接不佳或完全不可用的情况，但仍需要能够合理地运行。本指南提供了在设备离线时提供良好体验的更多信息和最佳实践。
🌐 Your app will encounter circumstances where the internet connection is sub-par or totally unavailable, and it still needs to work reasonably well. This guide offers more information and best practices for providing a great experience while the device is offline.
后台加载 JS 更新
🌐 Load JS updates in the background
当你发布应用更新时，用户将在更新中收到你的新版本代码。新版本会在下一次应用启动时或下一次调用Updates.reload()时下载。此行为同样适用于用户第一次打开应用时。
🌐 When you publish an update to your app, your users will receive the new version of your code in an update. The new version will download either the next time the app starts or the next time you call Updates.reload(). This behavior also applies the very first time the user opens your app.
Expo 提供了多种方式来下载你的 JS。它可以在下载新 JS 之前，通过 启动屏幕 或 AppLoading 组件 阻塞用户界面，或者可以立即显示旧版本的 JS，并在后台下载更新。如果你的用户必须始终使用最新版本，前者选项更好；如果你的网络连接较差并且需要立即显示内容，后者选项更好。
🌐 Expo offers multiple behaviors for how it should download your JS. It can either block the UI with a splash screen or AppLoading component until the new JS is downloaded, or it can immediately show an old version of your JS and download the update in the background. The former option is better if your users must have the latest version at all times; the latter option is better if you have a bad internet connection and need to show something right away.
要强制 JS 更新在后台运行（而不是在应用启动时同步检查和下载），请在 app.json 中将 updates.fallbackToCacheTimeout 设置为 0。你还可以监听新版本下载完成的事件。更多信息，请参见 配置更新。
🌐 To force JS updates to run in the background (rather than synchronously checking and downloading on app start), set updates.fallbackToCacheTimeout to 0 in app.json. You can also listen to see when a new version has finished downloading. For more information, see configuring updates.
下载后缓存你的资源
🌐 Cache your assets after downloading
默认情况下，当你发布应用更新时，你的所有资源（图片、字体等）都会上传到 Expo 的 CDN。下载后，你可以缓存它们，这样就不需要第二次下载。如果你发布了更改，缓存将失效，并会下载更改后的版本。
🌐 By default, all of your assets (images, fonts, and so on) are uploaded to Expo's CDN when you publish updates to your app. Once they're downloaded, you can cache them so you don't need to download them a second time. If you publish changes, the cache will be invalidated and the changed version will be downloaded.
将你的资源打包到独立的二进制文件中
🌐 Bundle your assets inside your standalone binary
Expo 可以在构建过程中将资源打包到你的独立二进制文件中，这样即使用户以前从未运行过你的应用，这些资源也可以立即使用。如果出现以下情况，这一点非常重要:
🌐 Expo can bundle assets into your standalone binary during the build process so that they will be available immediately, even if the user has never run your app before. This is important if:
- 你的用户第一次打开你的应用时可能没有互联网，或者
- 如果你的应用依赖大量资源才能使第一个屏幕正常运行。
EAS 构建
🌐 EAS Build
在使用 eas build 时，expo publish 不会 作为构建过程的一部分运行，因此 assetBundlePatterns 键在这种情况下不适用。相反，任何在你的代码库中显式 require() 的资源（包括在你的依赖中）都会被打包到你的二进制文件中。这与使用 Xcode 或 Android Studio 直接构建的常规 React Native 应用的行为相同。
🌐 When using eas build, expo publish is not run as part of the build process, so the assetBundlePatterns key doesn't apply in this case. Instead, any assets that are explicitly require() anywhere in your codebase (including in your dependencies) are bundled into your binary. This is the same behavior as with regular React Native apps built directly with Xcode or Android Studio.
经典构建
🌐 Classic builds
要将资源打包到二进制文件中，请在 app.json 中使用 assetBundlePatterns 键来提供项目目录中的路径列表：
🌐 To bundle assets in your binary, use the assetBundlePatterns key in app.json to provide a list of paths in your project directory:
下次运行 expo build 时，路径与给定模式匹配的图片将被打包到你的本地二进制文件中。
🌐 Images with paths matching the given patterns will be bundled into your native binaries next time you run expo build.
监听网络可用性的变化
🌐 Listen for changes in network availability
React Native 社区创建了 @react-native-community/netinfo 包，它会在你的设备的可达性发生变化时通知你。如果你发现没有网络连接，你可能需要更改你的用户界面（例如，显示一个横幅，或禁用某些功能）。
🌐 The React Native community created the @react-native-community/netinfo package, which informs you if your device's reachability changes. You may want to change your UI (for example, show a banner, or disable some functions) if you notice that there's no connection available.