CODEWITHSUNDEEP
ioslong-integerbackground-task
meaholik
meaholik

Reputation: 440

Long running background task in iOS

I know this is a very common question. I have read many answer but not found out the appropriate answer for me. That's why I post this question and hope someone will show me how to fix my code.

  1. I have function startUpdate to update location using CLLocationManager. In applicationDidEnterBackground method, I write something like below:

    [self startUpdate]; // position1 NSLog(@"applicationDidEnterBackground"); __block UIBackgroundTaskIdentifier bgTask; bgTask = [application beginBackgroundTaskWithExpirationHandler:^{ [application endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }];

    [self startUpdate]; // position2 // Start the long-running task and return immediately.

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ [self startUpdate]; // position3 [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://google.com"]]; });

    • I tried to put [self startUpdate] at one of three positions (position1, 2, 3) and sometime it works, sometime not, and I do not know why.

    • In case it works, updating just run in 3 minutes event. If I call startUpdate when app is in foreground, then put app to background, updating will last 15 minutes with real device, and more than 1hour with simulator ( I don't know exactly, after 1 hour, i thought it would last forever then I stop testing). So what is different between: startupdate in foreground-> go to background vs startupdate in background; simulator vs real device?

    • right after position3, I called following line to open safari [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://google.com"]]; But it does not work. So what types of task can be executed here, in background?

  2. I need to keep a service running forever. Some search results say that it's impossible. But some familiar apps did that (Facebook,... keeps service to receive notifications). How can they do that?

Thank you so much,

Upvotes: 0

Views: 999

Answers (1)

Paulw11
Paulw11

Reputation: 114773

The exact behaviour of location services has been clarified in the latest update to the Core Location documentation. It now states -

  • The standard location service delivers events normally while an app is running in the foreground. When your app is in the background, this service delivers events only when the location-updates background mode is enabled for the app. This service does not relaunch iOS apps that have been terminated.

  • The significant location change service delivers events normally while an app is running in the foreground or background. For a terminated iOS app, this service relaunches the app to deliver events. Use of this service requires “Always” authorization from the user.

So, it seems that for the best chance of continuing to receive location updates in the background you should switch to significant location change monitoring once you move to the background state and restore full location monitoring once you return to the foreground.

Upvotes: 1

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