Expo BackgroundFetch

一个提供用于执行后台获取任务的 API 的库。

已弃用：expo-background-fetch 库正在被 expo-background-task 中的新版本取代。expo-background-fetch 未收到补丁，将在即将发布的版本中移除。

expo-background-fetch 提供了执行 后台获取 任务的 API，允许你在后台定期运行特定代码来更新你的应用。该模块在底层使用 TaskManager Native API。

¥expo-background-fetch provides an API to perform background fetch tasks, allowing you to run specific code periodically in the background to update your app. This module uses TaskManager Native API under the hood.

已知的问题

¥Known issues

BackgroundFetch 仅在应用处于后台时有效，而在应用终止或设备重新启动时无效。你可以查看 相关的 GitHub 问题 了解更多详细信息。

¥BackgroundFetch only works when the app is backgrounded, not if the app was terminated or upon device reboot. You can check out the relevant GitHub issue for more details.

在 iOS 上，BackgroundFetch 库要求你使用 开发构建，因为 iOS Expo Go 应用中未启用后台获取。

¥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

¥Configuration

为了能够在 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.

如果你使用 CNG，所需的 UIBackgroundModes 配置将由预构建自动应用。

¥If you're using CNG, the required UIBackgroundModes configuration will be applied automatically by prebuild.

Usage

Below is an example that demonstrates how to use expo-background-fetch.

Triggering background fetches

Background fetches can be difficult to test because they can happen inconsistently. Fortunately, you can trigger background fetches manually when developing your apps.

For iOS, you can use the Instruments app on macOS to manually trigger background fetches:

1. Open the Instruments app. The Instruments app can be searched through Spotlight (⌘ + Space) or opened from /Applications/Xcode.app/Contents/Applications/Instruments.app
2. Select Time Profiler
3. Select your device / simulator and pick the Expo Go app
4. Press the Record button in the top left corner
5. Navigate to the Document Menu and select Simulate Background Fetch - Expo Go:

For Android, you can set the minimumInterval option of your task to a small number and background your application like so:

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API

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Methods

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;
  }
});

Interfaces

Enums

Permissions

Android

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.