Question

I would like to create a time counter in my app that shows the user how many minutes the app has been running the current session and total. How do I create such time counter and how do I save the value to the phone? I’m new to app developement.

Answer 1

You can use the NSDate and NSDateFormatter classes for this.

Here’s an example:

Declare an NSDate instance in your .m file:

@implementation MyClass 

NSDate *startDate;
BOOL stopTimer = NO;
//...    

-(void) showElapsedTime: (NSTimer *) timer {
    if(!startDate) {
        startDate = [NSDate date]; 
    }
    NSTimeInterval timeSinceStart = [[NSDate date] timeIntervalSinceDate:startDate];
    NSDate *newDate = [[NSDate alloc] initWithTimeInterval:timeSinceStart sinceDate:startDate];
    NSString *dateString = [NSDateFormatter localizedStringFromDate:newDate dateStyle: NSDateFormatterNoStyle timeStyle: NSDateFormatterShortStyle];


    //do something with dateString....

    if(stopTimer) {//base case
       [timer invalidate];
    }
    [newDate release];
}

- (void) startPolling {
    [NSTimer scheduledTimerWithTimeInterval:0.09f target:self selector:@selector(showElapsedTime:) userInfo:nil repeats:YES];
}

//...

@end