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POGetting user location every n minutes after app goes to background
 

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  1. POGetting user location every n minutes after app goes to background
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    <p>I am trying to implement the suggestions given in <a href="https://stackoverflow.com/questions/6347503/how-do-i-get-a-background-location-update-every-n-minutes-in-my-ios-application">this post</a>.</p> <p>Unfortunately the steps are not clear to me. I tried implementing those suggestions, but the backgroundTimeRemaining continues to decrease even after I start and stop locationServices. This is how I developed it:</p> <pre><code>- (void)applicationDidEnterBackground:(UIApplication *)application { UIApplication* app = [UIApplication sharedApplication]; bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ [app 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. self.timer = nil; [self initTimer]; }); } </code></pre> <p>initTimer:</p> <pre><code>- (void)initTimer { // Create the location manager if this object does not // already have one. if (nil == self.locationManager) self.locationManager = [[CLLocationManager alloc] init]; self.locationManager.delegate = self; [self.locationManager startMonitoringSignificantLocationChanges]; if (self.timer == nil) { self.timer = [NSTimer scheduledTimerWithTimeInterval:0.3 target:self selector:@selector(checkUpdates:) userInfo:nil repeats:YES]; } } </code></pre> <p>checkUpdates:</p> <pre><code>- (void)checkUpdates:(NSTimer *)timer{ UIApplication* app = [UIApplication sharedApplication]; double remaining = app.backgroundTimeRemaining; if(remaining &lt; 580.0) { [self.locationManager startUpdatingLocation]; [self.locationManager stopUpdatingLocation]; [self.locationManager startMonitoringSignificantLocationChanges]; } DbgLog(@"Reminaing %f", app.backgroundTimeRemaining); } </code></pre> <p>Does anyone have a suggestion on what might be wrong in my code? Both initTimer and checkUpdates are being called, but only during for the background execution time (+- 10 Mins). I want the app to update the location every n minutes "forever".</p> <p>My app's UIBackgroundModes is set to location.</p> <p><strong>UPDATE:</strong></p> <p>I am now resetting the timer on didUpdateToLocation and didFailWithError. But still the backgroundTimeRemaining keeps decreasing:</p> <pre><code>- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { NSLog(@"Did Update Location = %f / %f", [newLocation coordinate].latitude, [newLocation coordinate].longitude); UIApplication* app = [UIApplication sharedApplication]; bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ [app 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. [self initTimer]; }); } - (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error { [self.locationManager stopUpdatingLocation]; UIApplication* app = [UIApplication sharedApplication]; bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ [app endBackgroundTask:bgTask]; bgTask = UIBackgroundTaskInvalid; }]; // Start the long-running task and return immediately. [self initTimer]; dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{ // Do the work associated with the task. }); } </code></pre> <p>I am also invalidating the timer:</p> <pre><code>- (void)checkUpdates:(NSTimer *)timer{ UIApplication* app = [UIApplication sharedApplication]; double remaining = app.backgroundTimeRemaining; if(remaining &lt; 580.0 &amp;&amp; remaining &gt; 570.0) { [self.timer invalidate]; self.timer = nil; [self.locationManager startUpdatingLocation]; [self.locationManager stopUpdatingLocation]; } DbgLog(@"*************************Checking for updates!!!!!!!!!!! Reminaing %f", app.backgroundTimeRemaining); } </code></pre>
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