Run the task in the background thread in iOS, continue execution even when the application enters the background mode:

Question

How to execute execution in a background thread? Execution should continue in the background, even if the user clicks the home button.

Answer 1

Add these properties to your .h file

@property (nonatomic, strong) NSTimer *updateTimer; @property (nonatomic) UIBackgroundTaskIdentifier backgroundTask; 

Now suppose you have an action on a button → btnStartClicked then your method will look like this:

 -(IBAction)btnStartClicked:(UIButton *)sender { self.updateTimer = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(calculateNextNumber) userInfo:nil repeats:YES]; self.backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{ NSLog(@"Background handler called. Not running background tasks anymore."); [[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask]; self.backgroundTask = UIBackgroundTaskInvalid; }]; } -(void)calculateNextNumber{ @autoreleasepool { // this will be executed no matter app is in foreground or background } } 

and if you need to stop this method,

 - (IBAction)btnStopClicked:(UIButton *)sender { [self.updateTimer invalidate]; self.updateTimer = nil; if (self.backgroundTask != UIBackgroundTaskInvalid) { [[UIApplication sharedApplication] endBackgroundTask:self.backgroundTask]; self.backgroundTask = UIBackgroundTaskInvalid; } i = 0; }