Can't endBackgroundTask: no background task exists with identifier, or it may have already been ended

Question

I am using background task to run the timer in the background to update the user\'s location. It\'s declared as:

UIBackgroundTaskIdentifier bgTask;


        

Answer 1

I lose many days looking for the piece of code or framework that was causing this warning in the debug console Can't end BackgroundTask: no background task exists with identifier 2 (0x2), or it may have already been ended. Break in UIApplicationEndBackgroundTaskError() to debug.

Finally I've created an empty project Single View App. Only code generated by Xcode, I run the app on simulator, put it in background and I see the same warning. So I can say it's an iOS 13 issue. I hope Apple will fix it quickly because in Crashlytics I found some crash in my app caused by it.

Answer 2

You need to set bgTask = UIBackgroundTaskInvalid

in two moments

1. In the expiration handler.
2. After finishing your task.

I believe you are missing any of those two moments and that is why you are getting that error.

See apple example code:

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    bgTask = [application beginBackgroundTaskWithName:@"MyTask" expirationHandler:^{
        // Clean up any unfinished task business by marking where you
        // stopped or ending the task outright.
        [application endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    }];

    // Start the long-running task and return immediately.
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // Do the work associated with the task, preferably in chunks.

        [application endBackgroundTask:bgTask];
        bgTask = UIBackgroundTaskInvalid;
    });
}

link: https://developer.apple.com/documentation/backgroundtasks/bgtask?language=objc

Answer 3

Using Swift 5 - IOS 13.2.2 - Xcode 11.2 beta 2 (11B44) I managed to get rid of this error by

• enabling Push notifications in the Capabilities of the app

• Import the UserNotifications framework

• then add this code to

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

  let center = UNUserNotificationCenter.current()
        center.requestAuthorization(options:[.badge, .alert, .sound]) { (granted, error) in

            // If granted comes true you can enabled features based on authorization.
            guard granted else { return }
            DispatchQueue.main.async {
                application.registerForRemoteNotifications()
            }
        }

Answer 4

Are you using location update in the background?

If yes, add the below code at the time of getting location authorization from the user - Apple changed the default for allowsBackgroundLocationUpdates to NO from iOS 9 onwards.

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 9) {
    locationManager.allowsBackgroundLocationUpdates = YES;
}

Please make sure that you activated the 'Location updates' for background modes under your project 'Signing & Capabilities'. Otherwise it will crash.

Answer 5

I had the same issue and figured out the cause and solution!

Apple has fixed this issue in iOS 13.4 GM though I have workaround for the earlier versions.

While you should embrace using scenes when your app is run under iOS 13 and later, you can fully opt-out while you still support iOS 12 or earlier.

1. First, completely remove the “Application Scene Manifest” entry from Info.plist.
2. If there is a scene delegate class, remove it.
3. If there are any scene related methods in your app delegate, remove those methods.
4. If missing, add the property var window: UIWindow? to your app delegate.
5. Your app should now only use the app delegate and under iOS 13 it should have the same life cycle as iOS 12.

Happy coding!

Answer 6

Reproduced, here is my entire app:

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate
{
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool
    {
        return true
    }
}

And when I take it to background I get the same message. No storyboard or any other noise.