Problems in efficiently tracking the user in iOS 7 background mode - ios

Question

I am writing a code to constantly track the user applying CoreLocation. Since I cannot keep the GPS on all the time, I use StartMonitoringSignificantLocationChange in my AppDelegate to detect a significant change. I have registered for location in the UIBackgroundMode.
in didUpdateLocations method, I check the current distance from the previously recorded location. If it is significant, I apply StopMonitoringSignificantLocationChange and StartUpdatingLocation to get accurate locations. Meanwhile I initiate a timer (30 secs) to see whether the user is stationary or moving. If the user is not moving anymore, I apply StopUpdatingLocation and StartMonitoringSignificantLocationChange again.
I have also defined a background task in my AppDelegate: -(void)applicationWillResignActive:(UIApplication *)application as follows:
- (void)applicationWillResignActive:(UIApplication *)application
{
if (![[GeoSampleManager sharedManager] isLiveTracking])
{
GeoSampleManager *manager = [HTSGeoSampleManager sharedManager];
[manager.locationManager stopMonitoringSignificantLocationChanges];
self.bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask:self.bgTask];
self.bgTask = UIBackgroundTaskInvalid;
}];
[manager.locationManager startMonitoringSignificantLocationChanges];
}
}
I close the background task when the app eneters foreground:
- (void)applicationDidBecomeActive:(UIApplication *)application
{
if(self.bgTask != UIBackgroundTaskInvalid)
{
[[UIApplication sharedApplication] endBackgroundTask:self.bgTask];
self.bgTask = UIBackgroundTaskInvalid;
}
}
And here is my didUpdateLocations method:
- (void)locationManager:(CLLocationManager *)manager
didUpdateLocations:(NSArray *)locations
{
CLLocation* newLocation = [locations lastObject];
if(self.isLiveTracking)
{
//Test that the horizontal accuracy does not indicate an invalid measurement
if (newLocation.horizontalAccuracy < 0 || newLocation.horizontalAccuracy > 200)
{
return;
}
if([self.lastLocation distanceFromLocation:newLocation] > 0)
{
//Create and save a GeoSample
[GeoSampleManager createSampleForLocation:newLocation onTrip:self.activeTrip];
self.lastLocation = newLocation;
}
}
else
{
if([self.lastLocation distanceFromLocation:newLocation] > 0)
{
[self.locationManager stopMonitoringSignificantLocationChanges];
self.idleChecker = [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:#selector(checkIdle:) userInfo:nil repeats:YES];
[self.locationManager startUpdatingLocation];
self.isLiveTracking = YES;
}
}
}
And finally here is the timer method:
- (void)checkIdle:(NSTimer*)timer
{
if(abs([self.lastLocation.timestamp timeIntervalSinceNow]) >= 30.0)
{
//Stopping the idle-time checking timer
[self.idleChecker invalidate];
self.idleChecker = nil;
[self.locationManager stopUpdatingLocation];
[self.locationManager startMonitoringSignificantLocationChanges];
self.isLiveTracking = NO;
}
}
However, the app is suspended (sometimes after 5-10 secs, sometimes after 10 mins) and stops receiving location updates.Since I am struggling with this problem for more than a month and I have tried almost all possible solution, I really appreciate if you can help me to solve the issue in any way.
Cheers

Answer 1

Backgrounding tasks will die after 10 minutes unless the correct multitasking mode is set (such as a navigation app) in which case you need to keep the GPS on.
You will have to keep the GPS on or play a sound in the background. You say you cannot keep the GPS on all the time, but if this is the case then what you are seeing is likely the expected behavior (or i misread something).
Refer to the different CLLocationAccuracy constants available:
Available at: https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CoreLocationConstantsRef/Reference/reference.html#//apple_ref/c/data/kCLLocationAccuracyKilometer
extern const CLLocationAccuracy kCLLocationAccuracyBestForNavigation;
extern const CLLocationAccuracy kCLLocationAccuracyBest;
extern const CLLocationAccuracy kCLLocationAccuracyNearestTenMeters;
extern const CLLocationAccuracy kCLLocationAccuracyHundredMeters;
extern const CLLocationAccuracy kCLLocationAccuracyKilometer;
extern const CLLocationAccuracy kCLLocationAccuracyThreeKilometers;
At the very least this "may" help manage your GPS battery consumption if you do keep it running all the time.