ios, startMonitoringSignificantLocationChanges - sometimes breaks monitoring

cllocationmanager, ios

Solution

I can't say for sure if this is all of you problem but I would make the following changes:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
   // Moved to didFinishLaunching... you should not be recreating every time app
   // becomes active. You can check for locations key in the options Dictionary if
   // it is necessary to alter your setup based on background launch

   // Start location services
   locationManager = [[CLLocationManager alloc] init];
   locationManager.desiredAccuracy = kCLLocationAccuracyBest;

   // Only report to location manager if the user has traveled 1000 meters
   locationManager.distanceFilter = 1000.0f;
   locationManager.delegate = self;
   locationManager.activityType = CLActivityTypeAutomotiveNavigation;

   // Start monitoring significant locations here as default, will switch to
   // update locations on enter foreground
   [locationManager startMonitoringSignificantLocationChanges];

   // Hold in property to maintain reference
   self.locationManager = locationManager;
 }

Following your lead, this would be all that remains in your `didBecomeActive` method (I would use `willEnterForeground` instead):

- (void)willEnterForeground:(UIApplication *)application
{
   [self.locationManager stopMonitoringSignificantLocationChanges];
   [self.locationManager startUpdatingLocation];
}

Entering into background, go back to significant location changes only:

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    NSLog(@"Went to Background");
    // Need to stop regular updates first
    [self.locationManager stopUpdatingLocation];
    // Only monitor significant changes
    [self.locationManager startMonitoringSignificantLocationChanges];
}

In your delegate method, I recommend taking out all the conditional background testing. I am wrapping in background task identifier in case the app is in the background or goes into the background before finish. I am also responding on global thread so we don't block UI (optional):

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{

    UIApplication *app = [UIApplication sharedApplication];
    __block UIBackgroundTaskIdentifier locationUpdateTaskID = [app beginBackgroundTaskWithExpirationHandler:^{
        dispatch_async(dispatch_get_main_queue(), ^{
            if (locationUpdateTaskID != UIBackgroundTaskInvalid) {
                [app endBackgroundTask:locationUpdateTaskID];
                locationUpdateTaskID = UIBackgroundTaskInvalid;
            }
        });
    }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

        // You might consider what to do here if you do not ever get a location accurate enough to pass the test.
       // Also consider comparing to previous report and verifying that it is indeed beyond your threshold distance and/or recency. You cannot count on the LM not to repeat.
       if ([[locations lastObject] horizontalAccuracy] < 100.0f) {
            [self sendDataToServer:[locations lastObject]];
       }

        // Close out task Identifier on main queue
        dispatch_async(dispatch_get_main_queue(), ^{
            if (locationUpdateTaskID != UIBackgroundTaskInvalid) {
                [app endBackgroundTask:locationUpdateTaskID];
                locationUpdateTaskID = UIBackgroundTaskInvalid;
            }
        });
    });
}

See my project, TTLocationHandler

on Github for some more examples of using Core Location the way you wish to use it.

Problem

Original source