iphone - NSTimer 按秒/毫秒减少时间

Question

我正在开发一个 QuiZ 应用程序。它需要一个倒数计时器，因为我想在 75:00.00 (mm:ss.SS) 开始计时，并通过减少 1 毫秒将其减少到 00:00.00 (mm:ss.SS)。我想显示时间到的警报!当时间到达 00:00.00 (mm:ss.SS) 时。

我通过以下链接显示时间

Stopwatch using NSTimer incorrectly includes paused time in display

Answer 1

这是您问题的简单解决方案。

声明

@interface ViewController : UIViewController
{
    IBOutlet UILabel * result;      
    NSTimer * timer;                
    int currentTime;
}

- (void)populateLabelwithTime:(int)milliseconds;
-(IBAction)start;
-(IBAction)pause;
@end

定义

- (void)viewDidLoad
{
    [super viewDidLoad];

    currentTime = 270000000; // Since 75 hours = 270000000 milli seconds


}

-(IBAction)start{
   timer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:@selector(updateTimer:) userInfo:nil repeats:YES];

}
-(IBAction)pause{
    [timer invalidate];

}
- (void)updateTimer:(NSTimer *)timer {
    currentTime -= 10 ;
    [self populateLabelwithTime:currentTime];
     }
- (void)populateLabelwithTime:(int)milliseconds {
    int seconds = milliseconds/1000;
    int minutes = seconds / 60;
    int hours = minutes / 60;

    seconds -= minutes * 60;
    minutes -= hours * 60;

   NSString * result1 = [NSString stringWithFormat:@"%@%02dh:%02dm:%02ds:%02dms", (milliseconds<0?@"-":@""), hours, minutes, seconds,milliseconds%1000];
    result.text = result1;

}