background-processing

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Background Processing

后台任务处理

Register, schedule, and execute background work on iOS using the BackgroundTasks framework, background URLSession, and background push notifications.

使用BackgroundTasks框架、后台URLSession和后台推送通知，在iOS上注册、调度并执行后台任务。

Info.plist Configuration

Info.plist 配置

Every task identifier must be declared in

Info.plist

under

BGTaskSchedulerPermittedIdentifiers

, or

submit(_:)

throws

BGTaskScheduler.Error.Code.notPermitted

xml

<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>com.example.app.refresh</string>
    <string>com.example.app.db-cleanup</string>
    <string>com.example.app.export</string>
</array>

Also enable the required

UIBackgroundModes

xml

<key>UIBackgroundModes</key>
<array>
    <string>fetch</string>       <!-- Required for BGAppRefreshTask -->
    <string>processing</string>  <!-- Required for BGProcessingTask -->
</array>

In Xcode: target > Signing & Capabilities > Background Modes > enable "Background fetch" and "Background processing".

每个任务标识符必须在

Info.plist

的

BGTaskSchedulerPermittedIdentifiers

中声明，否则调用

submit(_:)

会抛出

BGTaskScheduler.Error.Code.notPermitted

错误。

xml

<key>BGTaskSchedulerPermittedIdentifiers</key>
<array>
    <string>com.example.app.refresh</string>
    <string>com.example.app.db-cleanup</string>
    <string>com.example.app.export</string>
</array>

同时需要启用所需的

UIBackgroundModes

：

xml

<key>UIBackgroundModes</key>
<array>
    <string>fetch</string>       <!-- BGAppRefreshTask 必需 -->
    <string>processing</string>  <!-- BGProcessingTask 必需 -->
</array>

在Xcode中的操作：目标项目 > 签名与功能 > 后台模式 > 启用“后台获取”和“后台处理”。

BGTaskScheduler Registration

BGTaskScheduler 注册

application(_:didFinishLaunchingWithOptions:)

. In SwiftUI, register in the

App

initializer.

需在应用启动完成之前注册任务处理器。在UIKit中，在

application(_:didFinishLaunchingWithOptions:)

方法中注册；在SwiftUI中，在

App

初始化器中注册。

UIKit Registration

UIKit 注册

swift

import BackgroundTasks

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil  // nil = main queue
        ) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
        }

        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.db-cleanup",
            using: nil
        ) { task in
            self.handleDatabaseCleanup(task: task as! BGProcessingTask)
        }

        return true
    }
}

swift

import BackgroundTasks

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil  // nil = 主队列
        ) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
        }

        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.db-cleanup",
            using: nil
        ) { task in
            self.handleDatabaseCleanup(task: task as! BGProcessingTask)
        }

        return true
    }
}

SwiftUI Registration

SwiftUI 注册

swift

import SwiftUI
import BackgroundTasks

@main
struct MyApp: App {
    init() {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil
        ) { task in
            BackgroundTaskManager.shared.handleAppRefresh(
                task: task as! BGAppRefreshTask
            )
        }
    }

    var body: some Scene {
        WindowGroup { ContentView() }
    }
}

swift

import SwiftUI
import BackgroundTasks

@main
struct MyApp: App {
    init() {
        BGTaskScheduler.shared.register(
            forTaskWithIdentifier: "com.example.app.refresh",
            using: nil
        ) { task in
            BackgroundTaskManager.shared.handleAppRefresh(
                task: task as! BGAppRefreshTask
            )
        }
    }

    var body: some Scene {
        WindowGroup { ContentView() }
    }
}

BGAppRefreshTask Patterns

BGAppRefreshTask 使用模式

Short-lived tasks (~30 seconds) for fetching small data updates. The system decides when to launch based on usage patterns.

swift

func scheduleAppRefresh() {
    let request = BGAppRefreshTaskRequest(
        identifier: "com.example.app.refresh"
    )
    request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("Could not schedule app refresh: \(error)")
    }
}

func handleAppRefresh(task: BGAppRefreshTask) {
    // Schedule the next refresh before doing work
    scheduleAppRefresh()

    let fetchTask = Task {
        do {
            let data = try await APIClient.shared.fetchLatestFeed()
            await FeedStore.shared.update(with: data)
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    // CRITICAL: Handle expiration -- system can revoke time at any moment
    task.expirationHandler = {
        fetchTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

短时长任务（约30秒），用于获取小型数据更新。系统会根据用户使用模式决定何时启动任务。

swift

func scheduleAppRefresh() {
    let request = BGAppRefreshTaskRequest(
        identifier: "com.example.app.refresh"
    )
    request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("无法调度应用刷新任务：\(error)")
    }
}

func handleAppRefresh(task: BGAppRefreshTask) {
    // 在执行任务前调度下一次刷新
    scheduleAppRefresh()

    let fetchTask = Task {
        do {
            let data = try await APIClient.shared.fetchLatestFeed()
            await FeedStore.shared.update(with: data)
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    // 关键：处理任务过期 —— 系统可能随时收回任务执行时间
    task.expirationHandler = {
        fetchTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

BGProcessingTask Patterns

BGProcessingTask 使用模式

Long-running tasks (minutes) for maintenance, data processing, or cleanup. Runs only when device is idle and (optionally) charging.

swift

func scheduleProcessingTask() {
    let request = BGProcessingTaskRequest(
        identifier: "com.example.app.db-cleanup"
    )
    request.requiresNetworkConnectivity = false
    request.requiresExternalPower = true
    request.earliestBeginDate = Date(timeIntervalSinceNow: 60 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("Could not schedule processing task: \(error)")
    }
}

func handleDatabaseCleanup(task: BGProcessingTask) {
    scheduleProcessingTask()

    let cleanupTask = Task {
        do {
            try await DatabaseManager.shared.purgeExpiredRecords()
            try await DatabaseManager.shared.rebuildIndexes()
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    task.expirationHandler = {
        cleanupTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

长时长任务（数分钟），用于执行维护、数据处理或清理工作。仅在设备空闲且（可选）充电时运行。

swift

func scheduleProcessingTask() {
    let request = BGProcessingTaskRequest(
        identifier: "com.example.app.db-cleanup"
    )
    request.requiresNetworkConnectivity = false
    request.requiresExternalPower = true
    request.earliestBeginDate = Date(timeIntervalSinceNow: 60 * 60)

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("无法调度处理任务：\(error)")
    }
}

func handleDatabaseCleanup(task: BGProcessingTask) {
    scheduleProcessingTask()

    let cleanupTask = Task {
        do {
            try await DatabaseManager.shared.purgeExpiredRecords()
            try await DatabaseManager.shared.rebuildIndexes()
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }

    task.expirationHandler = {
        cleanupTask.cancel()
        task.setTaskCompleted(success: false)
    }
}

BGContinuedProcessingTask (iOS 26+)

BGContinuedProcessingTask（iOS 26+）

A task initiated in the foreground by a user action that continues running in the background. The system displays progress via a Live Activity. Conforms to

ProgressReporting

Availability: iOS 26.0+, iPadOS 26.0+

Unlike

BGAppRefreshTask

and

BGProcessingTask

, this task starts immediately from the foreground. The system can terminate it under resource pressure, prioritizing tasks that report minimal progress first.

swift

import BackgroundTasks

func startExport() {
    let request = BGContinuedProcessingTaskRequest(
        identifier: "com.example.app.export",
        title: "Exporting Photos",
        subtitle: "Processing 247 items"
    )
    // .queue: begin as soon as possible if can't run immediately
    // .fail: fail submission if can't run immediately
    request.strategy = .queue

    BGTaskScheduler.shared.register(
        forTaskWithIdentifier: "com.example.app.export",
        using: nil
    ) { task in
        let continuedTask = task as! BGContinuedProcessingTask

        Task {
            await self.performExport(task: continuedTask)
        }
    }

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("Could not submit continued processing task: \(error)")
    }
}

func performExport(task: BGContinuedProcessingTask) async {
    let items = await PhotoLibrary.shared.itemsToExport()
    let progress = task.progress
    progress.totalUnitCount = Int64(items.count)

    for (index, item) in items.enumerated() {
        if Task.isCancelled { break }

        await PhotoExporter.shared.export(item)
        progress.completedUnitCount = Int64(index + 1)

        // Update the user-facing title/subtitle
        task.updateTitle(
            "Exporting Photos",
            subtitle: "\(index + 1) of \(items.count) complete"
        )
    }

    task.setTaskCompleted(success: !Task.isCancelled)
}

Check whether the system supports the resources your task needs:

swift

let supported = BGTaskScheduler.shared.supportedResources
if supported.contains(.gpu) {
    request.requiredResources = .gpu
}

由用户在前台触发、随后延续到后台执行的任务。系统会通过Live Activity展示任务进度，该任务遵循

ProgressReporting

协议。

兼容性： iOS 26.0+、iPadOS 26.0+

与

BGAppRefreshTask

和

BGProcessingTask

不同，此任务从前台立即启动。在资源紧张时，系统可能终止任务，优先保留报告进度最少的任务。

swift

import BackgroundTasks

func startExport() {
    let request = BGContinuedProcessingTaskRequest(
        identifier: "com.example.app.export",
        title: "Exporting Photos",
        subtitle: "Processing 247 items"
    )
    // .queue：如果无法立即运行，就尽快启动
    // .fail：如果无法立即运行，就提交失败
    request.strategy = .queue

    BGTaskScheduler.shared.register(
        forTaskWithIdentifier: "com.example.app.export",
        using: nil
    ) { task in
        let continuedTask = task as! BGContinuedProcessingTask

        Task {
            await self.performExport(task: continuedTask)
        }
    }

    do {
        try BGTaskScheduler.shared.submit(request)
    } catch {
        print("无法提交延续处理任务：\(error)")
    }
}

func performExport(task: BGContinuedProcessingTask) async {
    let items = await PhotoLibrary.shared.itemsToExport()
    let progress = task.progress
    progress.totalUnitCount = Int64(items.count)

    for (index, item) in items.enumerated() {
        if Task.isCancelled { break }

        await PhotoExporter.shared.export(item)
        progress.completedUnitCount = Int64(index + 1)

        // 更新面向用户的标题/副标题
        task.updateTitle(
            "Exporting Photos",
            subtitle: "\(index + 1) of \(items.count) complete"
        )
    }

    task.setTaskCompleted(success: !Task.isCancelled)
}

检查系统是否支持任务所需资源：

swift

let supported = BGTaskScheduler.shared.supportedResources
if supported.contains(.gpu) {
    request.requiredResources = .gpu
}

Background URLSession Downloads

后台URLSession 下载

Use

URLSessionConfiguration.background

for downloads that continue even after the app is suspended or terminated. The system handles the transfer out of process.

swift

class DownloadManager: NSObject, URLSessionDownloadDelegate {
    static let shared = DownloadManager()

    private lazy var session: URLSession = {
        let config = URLSessionConfiguration.background(
            withIdentifier: "com.example.app.background-download"
        )
        config.isDiscretionary = true
        config.sessionSendsLaunchEvents = true
        return URLSession(configuration: config, delegate: self, delegateQueue: nil)
    }()

    func startDownload(from url: URL) {
        let task = session.downloadTask(with: url)
        task.earliestBeginDate = Date(timeIntervalSinceNow: 60)
        task.resume()
    }

    func urlSession(
        _ session: URLSession,
        downloadTask: URLSessionDownloadTask,
        didFinishDownloadingTo location: URL
    ) {
        // Move file from tmp before this method returns
        let dest = FileManager.default.urls(
            for: .documentDirectory, in: .userDomainMask
        )[0].appendingPathComponent("download.dat")
        try? FileManager.default.moveItem(at: location, to: dest)
    }

    func urlSession(
        _ session: URLSession,
        task: URLSessionTask,
        didCompleteWithError error: (any Error)?
    ) {
        if let error { print("Download failed: \(error)") }
    }
}

Handle app relaunch — store and invoke the system completion handler:

swift

// In AppDelegate:
func application(
    _ application: UIApplication,
    handleEventsForBackgroundURLSession identifier: String,
    completionHandler: @escaping () -> Void
) {
    backgroundSessionCompletionHandler = completionHandler
}

// In URLSessionDelegate — call stored handler when events finish:
func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
    Task { @MainActor in
        self.backgroundSessionCompletionHandler?()
        self.backgroundSessionCompletionHandler = nil
    }
}

使用

URLSessionConfiguration.background

实现应用挂起或终止后仍能继续的下载任务，系统会在进程外处理传输操作。

swift

class DownloadManager: NSObject, URLSessionDownloadDelegate {
    static let shared = DownloadManager()

    private lazy var session: URLSession = {
        let config = URLSessionConfiguration.background(
            withIdentifier: "com.example.app.background-download"
        )
        config.isDiscretionary = true
        config.sessionSendsLaunchEvents = true
        return URLSession(configuration: config, delegate: self, delegateQueue: nil)
    }()

    func startDownload(from url: URL) {
        let task = session.downloadTask(with: url)
        task.earliestBeginDate = Date(timeIntervalSinceNow: 60)
        task.resume()
    }

    func urlSession(
        _ session: URLSession,
        downloadTask: URLSessionDownloadTask,
        didFinishDownloadingTo location: URL
    ) {
        // 在返回前将文件从临时目录移走
        let dest = FileManager.default.urls(
            for: .documentDirectory, in: .userDomainMask
        )[0].appendingPathComponent("download.dat")
        try? FileManager.default.moveItem(at: location, to: dest)
    }

    func urlSession(
        _ session: URLSession,
        task: URLSessionTask,
        didCompleteWithError error: (any Error)?
    ) {
        if let error { print("下载失败：\(error)") }
    }
}

处理应用重启 —— 存储并调用系统完成处理器：

swift

// 在AppDelegate中：
func application(
    _ application: UIApplication,
    handleEventsForBackgroundURLSession identifier: String,
    completionHandler: @escaping () -> Void
) {
    backgroundSessionCompletionHandler = completionHandler
}

// 在URLSessionDelegate中 —— 事件完成时调用存储的处理器：
func urlSessionDidFinishEvents(forBackgroundURLSession session: URLSession) {
    Task { @MainActor in
        self.backgroundSessionCompletionHandler?()
        self.backgroundSessionCompletionHandler = nil
    }
}

Background Push Triggers

后台推送触发

Silent push notifications wake your app briefly to fetch new content. Set

content-available: 1

in the push payload.

json

{ "aps": { "content-available": 1 }, "custom-data": "new-messages" }

Handle in AppDelegate:

swift

func application(
    _ application: UIApplication,
    didReceiveRemoteNotification userInfo: [AnyHashable: Any],
    fetchCompletionHandler completionHandler:
        @escaping (UIBackgroundFetchResult) -> Void
) {
    Task {
        do {
            let hasNew = try await MessageStore.shared.fetchNewMessages()
            completionHandler(hasNew ? .newData : .noData)
        } catch {
            completionHandler(.failed)
        }
    }
}

Enable "Remote notifications" in Background Modes and register:

swift

UIApplication.shared.registerForRemoteNotifications()

静默推送通知可短暂唤醒应用以获取新内容，需在推送 payload 中设置

content-available: 1

。

json

{ "aps": { "content-available": 1 }, "custom-data": "new-messages" }

在AppDelegate中处理：

swift

func application(
    _ application: UIApplication,
    didReceiveRemoteNotification userInfo: [AnyHashable: Any],
    fetchCompletionHandler completionHandler:
        @escaping (UIBackgroundFetchResult) -> Void
) {
    Task {
        do {
            let hasNew = try await MessageStore.shared.fetchNewMessages()
            completionHandler(hasNew ? .newData : .noData)
        } catch {
            completionHandler(.failed)
        }
    }
}

在后台模式中启用“远程通知”并完成注册：

swift

UIApplication.shared.registerForRemoteNotifications()

Common Mistakes

常见错误

1. Missing Info.plist identifiers

1. 缺少Info.plist中的任务标识符

swift

// DON'T: Submit a task whose identifier isn't in BGTaskSchedulerPermittedIdentifiers
let request = BGAppRefreshTaskRequest(identifier: "com.example.app.refresh")
try BGTaskScheduler.shared.submit(request)  // Throws .notPermitted

// DO: Add every identifier to Info.plist BGTaskSchedulerPermittedIdentifiers
// <string>com.example.app.refresh</string>

swift

// 错误：提交的任务标识符未在BGTaskSchedulerPermittedIdentifiers中声明
let request = BGAppRefreshTaskRequest(identifier: "com.example.app.refresh")
try BGTaskScheduler.shared.submit(request)  // 抛出.notPermitted错误

// 正确：将所有标识符添加到Info.plist的BGTaskSchedulerPermittedIdentifiers中
// <string>com.example.app.refresh</string>

2. Not calling setTaskCompleted(success:)

2. 未调用setTaskCompleted(success:)

swift

// DON'T: Return without marking completion -- system penalizes future scheduling
func handleRefresh(task: BGAppRefreshTask) {
    Task {
        let data = try await fetchData()
        await store.update(data)
        // Missing: task.setTaskCompleted(success:)
    }
}

// DO: Always call setTaskCompleted on every code path
func handleRefresh(task: BGAppRefreshTask) {
    let work = Task {
        do {
            let data = try await fetchData()
            await store.update(data)
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

swift

// 错误：未标记任务完成就返回 —— 系统会惩罚后续任务调度
func handleRefresh(task: BGAppRefreshTask) {
    Task {
        let data = try await fetchData()
        await store.update(data)
        // 缺失：task.setTaskCompleted(success:)
    }
}

// 正确：在所有代码路径中都调用setTaskCompleted
func handleRefresh(task: BGAppRefreshTask) {
    let work = Task {
        do {
            let data = try await fetchData()
            await store.update(data)
            task.setTaskCompleted(success: true)
        } catch {
            task.setTaskCompleted(success: false)
        }
    }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

3. Ignoring the expiration handler

3. 忽略expirationHandler

swift

// DON'T: Assume your task will run to completion
func handleCleanup(task: BGProcessingTask) {
    Task { await heavyWork() }
    // No expirationHandler -- system terminates ungracefully
}

// DO: Set expirationHandler to cancel work and mark completed
func handleCleanup(task: BGProcessingTask) {
    let work = Task { await heavyWork() }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

swift

// 错误：假设任务会执行完成
func handleCleanup(task: BGProcessingTask) {
    Task { await heavyWork() }
    // 未设置expirationHandler —— 系统会强制终止任务
}

// 正确：设置expirationHandler以取消正在执行的任务
func handleCleanup(task: BGProcessingTask) {
    let work = Task { await heavyWork() }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

4. Scheduling too frequently

4. 调度过于频繁

swift

// DON'T: Request refresh every minute -- system throttles aggressively
request.earliestBeginDate = Date(timeIntervalSinceNow: 60)

// DO: Use reasonable intervals (15+ minutes for refresh)
request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)
// earliestBeginDate is a hint -- the system chooses actual launch time

swift

// 错误：每分钟请求一次刷新 —— 系统会严格限制
request.earliestBeginDate = Date(timeIntervalSinceNow: 60)

// 正确：使用合理的时间间隔（刷新任务间隔15分钟以上）
request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)
// earliestBeginDate只是提示 —— 系统会选择实际启动时间

5. Over-relying on background time

5. 过度依赖后台执行时间

swift

// DON'T: Start a 10-minute operation assuming it will finish
func handleRefresh(task: BGAppRefreshTask) {
    Task { await tenMinuteSync() }
}

// DO: Design work to be incremental and cancellable
func handleRefresh(task: BGAppRefreshTask) {
    let work = Task {
        for batch in batches {
            try Task.checkCancellation()
            await processBatch(batch)
            await saveBatchProgress(batch)
        }
        task.setTaskCompleted(success: true)
    }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

swift

// 错误：启动一个10分钟的操作并假设它能完成
func handleRefresh(task: BGAppRefreshTask) {
    Task { await tenMinuteSync() }
}

// 正确：将任务设计为可增量执行且可取消
func handleRefresh(task: BGAppRefreshTask) {
    let work = Task {
        for batch in batches {
            try Task.checkCancellation()
            await processBatch(batch)
            await saveBatchProgress(batch)
        }
        task.setTaskCompleted(success: true)
    }
    task.expirationHandler = {
        work.cancel()
        task.setTaskCompleted(success: false)
    }
}

Review Checklist

审核检查清单

All task identifiers listed in
```
BGTaskSchedulerPermittedIdentifiers
```
Required
```
UIBackgroundModes
```
enabled (
```
fetch
```
,
```
processing
```
)
Tasks registered before app launch completes
```
setTaskCompleted(success:)
```
called on every code path
```
expirationHandler
```
set and cancels in-flight work
Next task scheduled inside the handler (re-schedule pattern)
```
earliestBeginDate
```
uses reasonable intervals (15+ min for refresh)
Background URLSession uses delegate (not async/closures)
Background URLSession file moved in
```
didFinishDownloadingTo
```
before return
```
handleEventsForBackgroundURLSession
```
stores and calls completion handler
Background push payload includes
```
content-available: 1
```
```
fetchCompletionHandler
```
called promptly with correct result
BGContinuedProcessingTask reports progress via
```
ProgressReporting
```
Work is incremental and cancellation-safe (
```
Task.checkCancellation()
```
)
No blocking synchronous work in task handlers

所有任务标识符都已在
```
BGTaskSchedulerPermittedIdentifiers
```
中列出
已启用所需的
```
UIBackgroundModes
```
（
```
fetch
```
、
```
processing
```
）
任务在应用启动完成前已注册
在所有代码路径中都调用了
```
setTaskCompleted(success:)
```
已设置
```
expirationHandler
```
并能取消正在执行的任务
在任务处理器内部调度了下一个任务（重新调度模式）
```
earliestBeginDate
```
使用了合理的时间间隔（刷新任务15分钟以上）
后台URLSession使用了代理（而非async/闭包）
在
```
didFinishDownloadingTo
```
方法返回前已移动后台URLSession的文件
```
handleEventsForBackgroundURLSession
```
存储并调用了完成处理器
后台推送payload包含
```
content-available: 1
```
及时调用
```
fetchCompletionHandler
```
并传入正确结果
BGContinuedProcessingTask通过
```
ProgressReporting
```
报告进度
任务可增量执行且支持取消（
```
Task.checkCancellation()
```
）
任务处理器中没有阻塞式同步操作

References

参考资料

See
```
references/background-task-patterns.md
```
for extended patterns, background URLSession edge cases, debugging with simulated launches, and background push best practices.
BGTaskScheduler
BGAppRefreshTask
BGProcessingTask
BGContinuedProcessingTask (iOS 26+)
BGContinuedProcessingTaskRequest (iOS 26+)
Using background tasks to update your app
Performing long-running tasks on iOS and iPadOS

查看
```
references/background-task-patterns.md
```
获取扩展模式、后台URLSession边缘案例、模拟启动调试方法，以及后台推送最佳实践。
BGTaskScheduler
BGAppRefreshTask
BGProcessingTask
BGContinuedProcessingTask (iOS 26+)
BGContinuedProcessingTaskRequest (iOS 26+)
Using background tasks to update your app
Performing long-running tasks on iOS and iPadOS

background-processing

Original

Translation

Background Processing

后台任务处理

Contents

目录

Info.plist Configuration

Info.plist 配置

BGTaskScheduler Registration

BGTaskScheduler 注册

UIKit Registration

UIKit 注册

SwiftUI Registration

SwiftUI 注册

BGAppRefreshTask Patterns

BGAppRefreshTask 使用模式

BGProcessingTask Patterns

BGProcessingTask 使用模式

BGContinuedProcessingTask (iOS 26+)

BGContinuedProcessingTask（iOS 26+）

Background URLSession Downloads

后台URLSession 下载

Background Push Triggers

后台推送触发

Common Mistakes

常见错误

1. Missing Info.plist identifiers

1. 缺少Info.plist中的任务标识符

2. Not calling setTaskCompleted(success:)

2. 未调用setTaskCompleted(success:)

3. Ignoring the expiration handler

3. 忽略expirationHandler

4. Scheduling too frequently

4. 调度过于频繁

5. Over-relying on background time

5. 过度依赖后台执行时间

Review Checklist

审核检查清单

References

参考资料