CountDown Timer ios tutorial?

Question

I'm making an application where the exams is going on, so when exam start the, time should start with that. For example 30 minutes and it should reduce like 29:59.

How can I implement this?

Can anyone please give me a sample example or a easy step by step tutorial that i can follow?

Answer 1

This code is used to create a countdown timer.

Code for .h file.

@interface UIMyContoller : UIViewController {

NSTimer *timer;
    IBOutlet UILabel *myCounterLabel;
}

@property (nonatomic, retain) UILabel *myCounterLabel;

-(void)updateCounter:(NSTimer *)theTimer;
-(void)countdownTimer;

@end

Code for .m file.

@implementation UIMyController
@synthesize myCounterLabel;

int hours, minutes, seconds;
int secondsLeft;

- (void)viewDidLoad {
    [super viewDidLoad];

    secondsLeft = 16925;
    [self countdownTimer];
}

- (void)updateCounter:(NSTimer *)theTimer {
    if(secondsLeft > 0 ) {
        secondsLeft -- ;
        hours = secondsLeft / 3600;
        minutes = (secondsLeft % 3600) / 60;
        seconds = (secondsLeft %3600) % 60;
        myCounterLabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", hours, minutes, seconds];
    } else {
        secondsLeft = 16925;
    }
}

-(void)countdownTimer {

    secondsLeft = hours = minutes = seconds = 0;
    if([timer isValid]) {
        [timer release];
    }
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];  
    timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(updateCounter:) userInfo:nil repeats:YES];
    [pool release];
}

Hope this helps you out.