Question

I’d like to use a NSTimer as a background task. I’ve written this code:

UIBackgroundTaskIdentifier bgTask;
        UIApplication  *app = [UIApplication sharedApplication];
        bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
            [app endBackgroundTask:bgTask];
        }];
        self.silenceTimer = [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(findlocation:) userInfo:nil repeats:NO];

But it doesn’t fire the findlocation method after 30 seconds. Please guide me how to do this.

Answer 1

Try this code:

dispatch_queue_t backgroundQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
 dispatch_source_t timerSource = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, backgroundQueue);
 dispatch_source_set_timer(timerSource, dispatch_time(DISPATCH_TIME_NOW, 0), 10.0*NSEC_PER_SEC, 0*NSEC_PER_SEC);
 dispatch_source_set_event_handler(timerSource, ^{
     if(queue)
         [self findlocation];
 });
 dispatch_resume(timerSource);