Handle NSNotification while scrolling a inner UITableView - ios

Question

I need some UIViewControllers that receive a NSNotification from the app delegate. It's like a timer, but every UIViewController handle your way. My problem is: when I interact with user interface, the UIViewController doesn't receive the notification, causing problems.
Here is my code in AppDelegate:
-(void)updateCounter:(NSTimer *)theTimer{
[[NSNotificationCenter defaultCenter] postNotificationName:TimeTickNotification object:nil];
}
//*called by some trigger in the app
-(void) startTimer{
timer = [NSTimer
scheduledTimerWithTimeInterval:0.5
target:self
selector:#selector(updateCounter:)
userInfo:nil
repeats:YES];
}
I am handling the notifications in each UIViewController like this:
-(void) updateGlobalTime:(NSNotification *) notification{
totalTime = [NSNumber numberWithFloat:([ficha.tempoTotal floatValue] + STEP)];
}
-(void) viewWillAppear:(BOOL)animated {
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(updateGlobalTime:)
name:TimeTickNotification
object:nil];
}
What should I do to interact with UI and update it at same time? Maybe the NSNotification is not being thrown while user interacts with UI.

Answer 1

You need to make sure you're updating any UI on the main thread. If you want to update the UI to have the new totalTime in a label or something, make sure the setText: function is running on the main thread. You can accomplish that with GCD, like this:
-(void) updateGlobalTime:(NSNotification *) notification{
totalTime = [NSNumber numberWithFloat:([ficha.tempoTotal floatValue] + STEP)];
// Update label on main thread
dispatch_async(dispatch_get_main_queue(), ^{
[label setText:totalTime];
});
}

Answer 2

The solution was to use NSRunLoop, as following:
NSRunLoop *runloop = [NSRunLoop currentRunLoop];
timer = [NSTimer
scheduledTimerWithTimeInterval:0.5
target:self
selector:#selector(updateCounter:)
userInfo:nil
repeats:YES];
[runloop addTimer:timer forMode:NSRunLoopCommonModes];
[runloop addTimer:timer forMode:UITrackingRunLoopMode];