Basic iphone timer example

Question

Okay, I have searched online and even looked in a couple of books for the answer because I can't understand the apple documentation for the NSTimer. I am trying to implement 2 timers on the same view that each have 3 buttons (START - STOP - RESET).

The first timer counts down from 2 minutes and then beeps.

The second timer counts up from 00:00 indefinitely.

I am assuming that all of the code will be written in the methods behind the 3 different buttons but I am completely lost trying to read the apple documentation. Any help would be greatly appreciated.

Answer 1

Basically what you want is an event that fires every 1 second, or possibly at 1/10th second intervals, and you'll update your UI when the timer ticks.

The following will create a timer, and add it to your run loop. Save the timer somewhere so you can kill it when needed.

- (NSTimer*)createTimer {

    // create timer on run loop
    return [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTicked:) userInfo:nil repeats:YES];
}

Now write a handler for the timer tick:

- (void)timerTicked:(NSTimer*)timer {

    // decrement timer 1 … this is your UI, tick down and redraw
    [myStopwatch tickDown];
    [myStopwatch.view setNeedsDisplay]; 

    // increment timer 2 … bump time and redraw in UI
    …
}

If the user hits a button, you can reset the counts, or start or stop the ticking. To end a timer, send an invalidate message:

- (void)actionStop:(id)sender {

    // stop the timer
    [myTimer invalidate];
}

Hope this helps you out.