CLLocationManager doesn't start location updates when application did enter background - ios

Question

In my app I need to perform location updates in background. For this purpose I registered my location tracking object as observer like this:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(start)
name:UIApplicationDidEnterBackgroundNotification
object:nil];
and this is the method that starts updating location:
- (void)start
{
NSInteger downloadsCount = [[SGDataManager sharedInstance] countOfActiveDownloads];
NSInteger uploadsCount = [[SGDataManager sharedInstance] countOfActiveUploads];
if (downloadsCount + uploadsCount > 0)
{
[self.locationManager startUpdatingLocation];
}
}
However location updates never start. But if I change UIApplicationDidEnterBackgroundNotification to UIApplicationWillResignActiveNotification then the location updates work perfectly in background. So how do I make it work for did enter background notification?
I want to note that location updates background mode is enabled for my app

Answer 1

When your application goes in to background it has finite time to finish tasks. After that time the tasks will be suspended.
Try to put your UpdateLocation into a background task, like here:
http://hayageek.com/ios-long-running-background-task/
This example also uses location updates while going into background.
EDIT:
In my opinion it's a CoreLocation bug. It could be something like: startUpdatingLocation method finishes, the background task finishes, but there is still something happening in some other thread that CoreLocation spawned and the app suspends this thread because it goes into background. It's just a guess though.
Either way, here's a workaround: extend your app lifetime in background. Do not end the background task when startUpdatingLocation finishes, let it run for a couple of seconds.
__block UIBackgroundTaskIdentifier back = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask: back];
back = UIBackgroundTaskInvalid;
}];
[manager startUpdatingLocation];
This code will let your app run in background for a couple of minutes. You can create a timer that will suspend it faster if you like
NSTimer* killBackgroundTaskTimer = [NSTimer scheduledTimerWithTimeInterval: 10 target: self
selector: #selector(killBackgroundTask:) userInfo: nil repeats: NO];
-(void) callAfterSixtySecond:(NSTimer*) t
{
[application endBackgroundTask: back];
back = UIBackgroundTaskInvalid;
}

Answer 2

You need to enable project Background Modes capabilities.
Go to project properties >> Capabilities section.
Select Background Modes and click switch to turn ON.
In background mode check Location updates true.
This will enable location updates in background mode.