问题描述

timeinterval中获取负值？

需要做一个比较日期的计时器，结果总是随机停，有时返回时间间隔的值，好像只有时间间隔是负值的时候才能正常工作。代码：

-(IBAction)startTimer:(id)sender{    if (timer == nil) {        [startButton setTitle:@""Start"" forState:UIControlStateNormal];        timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerAction:) userInfo:nil repeats:YES];        date = [NSDate dateWithTimeIntervalSinceNow:testTask.timeInterval]; //instance variable    } else {        [startButton setTitle:@""Stop"" forState:UIControlStateNormal];        [timer invalidate];        timer = nil;    }}-(void)timerAction:(NSTimer *)t{    NSDate *currentDate = [NSDate date];    NSTimeInterval updatedTimeInterval = [date timeIntervalSinceDate:currentDate];    if (updatedTimeInterval > 0){        if (self.timer)        {            [self timerExpired];            [self.timer invalidate];            self.timer = nil;        }    }    else    {        testTask.timeInterval = updatedTimeInterval;        NSLog(@""%.2f"" testTask.timeInterval);        NSError *error;        if (![self.context save:&error]) {            NSLog(@""couldn't save: %@"" [error localizedDescription]);        }    }    NSUInteger seconds = (NSUInteger)round(testTask.timeInterval);    NSString *string = [NSString stringWithFormat:@""%02u:%02u:%02u""                        seconds / 3600 (seconds / 60) % 60 seconds % 60];    timerLabel.text = string;    NSLog(@""%f"" testTask.timeInterval);}