NSDate countdown from NOW to NSDate

问题

How can I show a countdown in HH:mm:ss format from NOW to a desired NSDate that will happen in the future?

回答1:

You have to use a timer for ticking the date.

Store a future date, and keep on substracting future date - [nsdate today]...

Calculate the time in seconds and calculate it into Hours, minutes, seconds...

//Make two properties NSDate *nowDate, *futureDate

futureDate=...;

nowDate=[NSDate date];

long elapsedSeconds=[nowDate timeIntervalSinceDate:futureDate];
NSLog(@"Elaped seconds:%ld seconds",elapsedSeconds);

NSInteger seconds = elapsedSeconds % 60;
NSInteger minutes = (elapsedSeconds / 60) % 60;
NSInteger hours = elapsedSeconds / (60 * 60);
NSString *result= [NSString stringWithFormat:@"%02ld:%02ld:%02ld", hours, minutes, seconds];

This will come handy for you...kindly check the project...

回答2:

Start at the documentation.

NSDate *future = // whatever

[NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(updateCounter:) userInfo:nil repeats:YES];

- (void)updateCounter:(NSTimer *)tmr
{
    NSTimeInterval iv = [future timeIntervalSinceNow];
    int h = iv / 3600;
    int m = (iv - h * 3600) / 60;
    int s = iv - h * 3600 - m * 60;
    aUILabel.text = [NSString stringWithFormat:@"%02d:%02d:%02d", h, m, s];
    if (h + m + s <= 0) {
        [tmr invalidate];
    }
}

回答3:

Give this code a shot:

NSTimer* timer= [NSTimer scheduledTimerWithInterval: [self.futureDate timeIntervalSinceNow] target: self selector: @selector(countdown:) userInfo: nil, repeats: YES];

The countdown: method:

- (void) countdown: (NSTimer*) timer
{
    if( [self.futureDate timeIntervalSinceNow] <= 0)
    {
        [timer invalidate];
        return;
    }
    NSDateComponents* comp= [ [NSCalendar currentCalendar] components: NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit startingDate: [NSDate date] toDate: self.futureDate options: 0];
    NSLog(@"%lu:%lu:%lu", comp.hour,comp.minute.comp.second);
}

来源：https://stackoverflow.com/questions/14406002/nsdate-countdown-from-now-to-nsdate

标签

objective-c

nsdate

countdown