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Expo BackgroundFetch
一个提供用于执行后台获取任务的 API 的库。
警告 已弃用:
expo-background-fetch库正在被expo-background-task的新版本替换。expo-background-fetch不再接收补丁,并将在即将发布的版本中被移除。
expo-background-fetch 提供了一个 API 来执行 background fetch 任务,使你能够在后台定期运行特定代码以更新你的应用。该模块在底层使用了 TaskManager 原生 API。
已知问题 iOS
🌐 Known issues
BackgroundFetch 仅在应用处于后台时有效,如果应用已被终止或设备重启,则无效。你可以查看相关的 GitHub 问题了解更多详情。
在 iOS 上,BackgroundFetch 库要求你使用 开发版本,因为在 iOS Expo Go 应用中未启用后台获取功能。
🌐 On iOS the BackgroundFetch library requires you to use a development build since Background Fetch is not enabled in the iOS Expo Go app.
安装
🌐 Installation
If you are installing this in an existing React Native app, make sure to install expo in your project.
配置 iOS
🌐 Configuration
要在 iOS 上运行后台获取任务,你需要将 fetch 值添加到应用的 Info.plist 文件中的 UIBackgroundModes 数组中。这是后台获取正常工作所必需的。
🌐 To be able to run background fetch tasks on iOS, you need to add the fetch value to the UIBackgroundModes array in your app's Info.plist file. This is required for background fetch to work properly.
如果你正在使用 CNG,所需的 UIBackgroundModes 配置将会由预构建自动应用。
用法
🌐 Usage
下面是一个演示如何使用 expo-background-fetch 的示例。
🌐 Below is an example that demonstrates how to use expo-background-fetch.
触发后台获取
🌐 Triggering background fetches
后台获取可能很难测试,因为它们可能发生不一致。幸运的是,在开发应用时,你可以手动触发后台获取。
🌐 Background fetches can be difficult to test because they can happen inconsistently. Fortunately, you can trigger background fetches manually when developing your apps.
对于 iOS,你可以在 macOS 上使用 Instruments 应用手动触发后台获取:
🌐 For iOS, you can use the Instruments app on macOS to manually trigger background fetches:
- 打开 Instruments 应用。可以通过 Spotlight (Cmd ⌘ + 空格) 搜索 Instruments 应用,或者从
/Applications/Xcode.app/Contents/Applications/Instruments.app打开 - 选择
Time Profiler - 选择你的设备/模拟器,然后选择
Expo Go应用 - 按左上角的
Record按钮 - 导航到
Document菜单并选择Simulate Background Fetch - Expo Go:
对于 Android,你可以将任务的 minimumInterval 选项设置为一个小数字,并像这样将应用置于后台:
🌐 For Android, you can set the minimumInterval option of your task to a small number and background your application like so:
async function registerBackgroundFetchAsync() { return BackgroundFetch.registerTaskAsync(BACKGROUND_FETCH_TASK, { minimumInterval: 1 * 60, // task will fire 1 minute after app is backgrounded }); }
应用接口
🌐 API
import * as BackgroundFetch from 'expo-background-fetch';
Methods
Deprecated: Use
getStatusAsync()fromexpo-background-taskinstead. Theexpo-background-fetchpackage has been deprecated.
Gets a status of background fetch.
Promise<BackgroundFetchStatus | null>Returns a promise which fulfils with one of BackgroundFetchStatus enum values.
Deprecated: Use
registerTaskAsync()fromexpo-background-taskinstead. Theexpo-background-fetchpackage has been deprecated.
Registers background fetch task with given name. Registered tasks are saved in persistent storage and restored once the app is initialized.
Promise<void>Example
import * as BackgroundFetch from 'expo-background-fetch'; import * as TaskManager from 'expo-task-manager'; TaskManager.defineTask(YOUR_TASK_NAME, () => { try { const receivedNewData = // do your background fetch here return receivedNewData ? BackgroundFetch.BackgroundFetchResult.NewData : BackgroundFetch.BackgroundFetchResult.NoData; } catch (error) { return BackgroundFetch.BackgroundFetchResult.Failed; } });
Deprecated: Use the
registerTaskAsync()method from expo-background-task package, and specifyBackgroundTaskOptionsargument instead, when setting task interval time.
Sets the minimum number of seconds that must elapse before another background fetch can be initiated. This value is advisory only and does not indicate the exact amount of time expected between fetch operations.
This method doesn't take any effect on Android. It is a global value which means that it can overwrite settings from another application opened through Expo Go.
Promise<void>A promise which fulfils once the minimum interval is set.
Deprecated: Use
unregisterTaskAsync()fromexpo-background-taskinstead. Theexpo-background-fetchpackage has been deprecated.
Unregisters background fetch task, so the application will no longer be executing this task.
Promise<void>A promise which fulfils when the task is fully unregistered.
Interfaces
Enums
This return value is to let iOS know what the result of your background fetch was, so the platform can better schedule future background fetches. Also, your app has up to 30 seconds to perform the task, otherwise your app will be terminated and future background fetches may be delayed.
BackgroundFetchStatus.Denied = 1The user explicitly disabled background behavior for this app or for the whole system.
BackgroundFetchStatus.Restricted = 2Background updates are unavailable and the user cannot enable them again. This status can occur when, for example, parental controls are in effect for the current user.
权限
🌐 Permissions
安卓
🌐 Android
在 Android 上,这个模块可能会在设备启动时进行监听。它对于继续执行由 startOnBoot 启动的任务是必要的。它还会保持即将进入闲置和快速休眠状态的设备“唤醒”,以提高任务的可靠性。因此,RECEIVE_BOOT_COMPLETED 和 WAKE_LOCK 权限都会被自动添加。
🌐 On Android, this module might listen when the device is starting up. It's necessary to continue working on tasks started with startOnBoot. It also keeps devices "awake" that are going idle and asleep fast, to improve reliability of the tasks. Because of this both the RECEIVE_BOOT_COMPLETED and WAKE_LOCK permissions are added automatically.