iOS开发：用NSTimer实现倒计时

首先定义NSTimerNSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector（timerFireMethod:） userInfo:nil repeats:YES];倒计时在timer的触发方法里完成 - （void）timerFireMethod:（NSTimer *）timer{ NSCalendar *calendar = [NSCalendar currentCalendar]; NSDateComponents *components = [[NSDateComponents alloc] init]; [components setYear:2012]; [components setMonth:8]; [components setDay:13]; [components setHour:12]; [components setMinute:0]; [components setSecond:0]; NSDate *fireDate = [calendar dateFromComponents:components];//目标时间 NSDate *today = [NSDate date];//当前时间 unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit; NSDateComponents *d = [calendar components:unitFlags fromDate:today toDate:fireDate options:0];//计算时间差 auctionTime.text = [NSString stringWithFormat:@"%d天%d小时%d%分%d秒", [d day], [d hour], [d minute], [d second]];//倒计时显示}这样就完成了倒计时。不过如果有专门的服务器时，要把服务器和自己本机的时间差考虑进去