iOS开发 倒计时

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

- (void)timerFireMethod:(NSTimer*)theTimer{
    
    id obj = [theTimer userInfo];
    NSDateFormatter *f1 = [[NSDateFormatter alloc] init];
    [f1 setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    
    NSDate *theDay = [f1 dateFromString:(NSString*)obj];
//    [f1 release];
    
    NSCalendar *cal = [NSCalendar currentCalendar];//定义一个NSCalendar对象
    
    NSDate *today = [NSDate date];//得到当前时间
    
    //用来得到具体的时差
    unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
    NSDateComponents *d = [cal components:unitFlags fromDate:today toDate:theDay options:0];
    
    NSString *countdown = [NSString stringWithFormat:@"%d年%d月%d日%d时%d分%d秒", [d year],[d month],[d day], [d hour], [d minute], [d second]];
    NSLog(@"countDowm== %@",countdown);
    
//    self.timeLabel.text = countdown;
    
    
}