iOS 13 中的后台任务不会 运行 多次

Question

我正在使用新的 iOS13 后台任务框架，实现了 BGAppRefreshTask 类型。我不知道我做错了什么，因为我尝试了很多不同的方法，但后台任务从未执行过一次以上 我想定期将用户的位置更新到服务器，我启用了后台位置更新和后台获取功能。 我尝试了方法

performFetchWithCompletionHandler

但它在 iOS 13 中贬值了，我正在 iPhone 11 中进行测试，它永远不会工作，除非我 运行 从调试 > 模拟后台获取 除此之外，我还尝试了我在 WWDC 2019

中看到的这段代码

在这里

应用委托：

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    
     LocationHelper.shared.locationManager = CLLocationManager()
            
            if #available(iOS 13.0, *) {
                BGTaskScheduler.shared.register(forTaskWithIdentifier: "com.testApp.updateLocation", using: nil) { task in
                    //This task is cast with processing request (BGProcessingTask)
                    self.handleLocationUpdateTask(task: task as! BGAppRefreshTask)
                }
                self.registerLocalNotification()
            } else {
                // Fallback on earlier versions
            }
    
    }

    func applicationDidEnterBackground(_ application: UIApplication) {
            if #available(iOS 13.0, *) {
                cancelAllPendingBGTask()
                scheduleLocationUpdate()
            } else {
                // Fallback on earlier versions
            }
        }

    func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
            // For iOS < 13
            // fetch data from internet now
            if #available(iOS 13.0, *) {
            }
            else {
                LocationHelper.shared.locationManager.startMonitoringSignificantLocationChanges()
                
                fetchSomeData(completion: { (bool) in
                    if bool {
                        LocationHelper.shared.locationManager.stopMonitoringSignificantLocationChanges()
                        completionHandler(.newData)
                    } else {
                        LocationHelper.shared.locationManager.stopMonitoringSignificantLocationChanges()
                        completionHandler(.failed)
                    }
                })
            }
        }

func registerLocalNotification() {
        let notificationCenter = UNUserNotificationCenter.current()
        let options: UNAuthorizationOptions = [.alert, .sound, .badge]
        
        notificationCenter.requestAuthorization(options: options) {
            (didAllow, error) in
            if !didAllow {
                print("User has declined notifications")
            }
        }
    }
    
    //MARK: Register BackGround Tasks
    
    @available(iOS 13.0, *)
    func scheduleLocalNotification() {
        let notificationCenter = UNUserNotificationCenter.current()
        notificationCenter.delegate = self
        notificationCenter.getNotificationSettings { (settings) in
            if settings.authorizationStatus == .authorized {
                self.fireNotification()
            }
        }
    }
    
    @available(iOS 13.0, *)
    func scheduleLocationUpdate() {
        let request = BGAppRefreshTaskRequest(identifier: "com.testApp.updateLocation") // BGProcessingTaskRequest(identifier: "com.testApp.updateLocation")
        request.earliestBeginDate = Date(timeIntervalSinceNow: 10) // fetch data after 10 secs.
        //Note :: EarliestBeginDate should not be set to too far into the future.
        do {
            try BGTaskScheduler.shared.submit(request)
        } catch {
            print("Could not schedule image fetch: (error)")
        }
    }
    
    @available(iOS 13.0, *)
    func handleLocationUpdateTask(task: BGAppRefreshTask) {
        scheduleLocationUpdate()
        
        let queue = OperationQueue()
        queue.maxConcurrentOperationCount = 1
        let lastOperation = queue.operations.last!
        
        task.expirationHandler = {
            queue.cancelAllOperations()
        }
        
        
        lastOperation.completionBlock = {
            task.setTaskCompleted(success: !lastOperation.isCancelled)
        }
        
        queue.addOperation {
            self.fetchSomeData { (bool) in
                self.scheduleLocalNotification()
                task.setTaskCompleted(success: bool)
            }
        }
        
    }
    
    @available(iOS 13.0, *)
    func cancelAllPendingBGTask() {
        BGTaskScheduler.shared.cancelAllTaskRequests()
    }
    
    func fireNotification() {
        // Create Notification Content
        let notificationContent = UNMutableNotificationContent()
        
        // Configure Notification Content
        notificationContent.title = Constants.Values.appName.rawValue
        notificationContent.body = "The app just tried to run a background task on \(UserDefaults.standard.string(forKey: "LastBackgroundFetch") ?? "NEVER")"
        notificationContent.badge = 1
        if #available(iOS 12.0, *) {
            notificationContent.sound = .defaultCriticalSound(withAudioVolume: .infinity)
        } else {
            // Fallback on earlier versions
        }
        
        // Add Trigger
        let notificationTrigger = UNTimeIntervalNotificationTrigger(timeInterval: 1.0, repeats: false)
        
        // Create Notification Request
        let notificationRequest = UNNotificationRequest(identifier: "local_notification", content: notificationContent, trigger: notificationTrigger)
        UNUserNotificationCenter.current().delegate = self
        // Add Request to User Notification Center
        UNUserNotificationCenter.current().add(notificationRequest) { (error) in
            if let error = error {
                print("Unable to Add Notification Request (\(error), \(error.localizedDescription))")
            }
        }
    }

func fetchSomeData(completion: @escaping (Bool) -> () ) {
        
        LocationHelper.shared.updateUser { (bool) in
            let date = DateFormatter.sharedDateFormatter.string(from: Date())
            UserDefaults.standard.set(date, forKey: "LastBackgroundFetch")
            completion(bool)
        }
    }

在这段代码中，我能够根据苹果的文档测试后台模式，方法是暂停应用程序，然后在调试器中键入这段代码，然后恢复

e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateLaunchForTaskWithIdentifier:@"com.FindFamily.updateLocation"]

即使在这之后，代码只 运行 一次然后停止，实际上它应该继续调用自己，因为 scheduleLocationUpdate() 在函数 handleLocationUpdateTask(task:) 中被调用，这将被调用每 10 秒后（大约）

Answer 1

我发现了问题 我正在使用后台进程来实现一些没有它就可以实现的事情 我在功能部分启用了后台位置更新，它开始在后台为我提供持续更新。