IOS开发代码分享之用nstimer实现倒计时功能

//- (void)timerFireMethod:(NSTimer *)theTimer{BOOL timeStart = YES;NSCalendar *cal = [NSCalendar currentCalendar];//定义一个NSCalendar对象NSDateComponents *endTime = [[NSDateComponents alloc] init];    //初始化目标时间...

NSDate *today = [NSDate date];    //得到当前时间

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];NSDate *dateString = [dateFormatter dateFromString:todate];NSString *overdate = [dateFormatter stringFromDate:dateString];//    NSLog(@"overdate=%@",overdate);static int year;static int month;static int day;static int hour;static int minute;static int second;if(timeStart) {//从NSDate中取出年月日，时分秒，但是只能取一次year = [[overdate substringWithRange:NSMakeRange(0, 4)] intValue];month = [[overdate substringWithRange:NSMakeRange(5, 2)] intValue];day = [[overdate substringWithRange:NSMakeRange(8, 2)] intValue];hour = [[overdate substringWithRange:NSMakeRange(11, 2)] intValue];minute = [[overdate substringWithRange:NSMakeRange(14, 2)] intValue];second = [[overdate substringWithRange:NSMakeRange(17, 2)] intValue];timeStart= NO;}

[endTime setYear:year];[endTime setMonth:month];[endTime setDay:day];[endTime setHour:hour];[endTime setMinute:minute];[endTime setSecond:second];NSDate *overTime = [cal dateFromComponents:endTime]; //把目标时间装载入date//用来得到具体的时差，是为了统一成北京时间unsigned int unitFlags = NSYearCalendarUnit| NSMonthCalendarUnit| NSDayCalendarUnit| NSHourCalendarUnit| NSMinuteCalendarUnit| NSSecondCalendarUnit;NSDateComponents *d = [cal components:unitFlags fromDate:today toDate:overTime options:0];NSString *t = [NSString stringWithFormat:@"%d", [d day]];NSString *h = [NSString stringWithFormat:@"%d", [d hour]];NSString *fen = [NSString stringWithFormat:@"%d", [d minute]];if([d minute] < 10) {fen = [NSString stringWithFormat:@"0%d",[d minute]];}NSString *miao = [NSString stringWithFormat:@"%d", [d second]];if([d second] < 10) {miao = [NSString stringWithFormat:@"0%d",[d second]];}//    NSLog(@"===%@天 %@:%@:%@",t,h,fen,miao);[_longtime setText:[NSString stringWithFormat:@"%@天 %@:%@:%@",t,h,fen,miao]];if([d second] > 0) {//计时尚未结束，do_something//        [_longtime setText:[NSString stringWithFormat:@"%@:%@:%@",d,fen,miao]];} else if([d second] == 0) {//计时结束 do_something

} else{//计时器失效[theTimer invalidate];}