用nstimer实现倒计时

用nstimer实现倒计时

//

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

//

- (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(, )] intValue];

        month = [[overdate substringWithRange:NSMakeRange(, )] intValue];

        day = [[overdate substringWithRange:NSMakeRange(, )] intValue];

        hour = [[overdate substringWithRange:NSMakeRange(, )] intValue];

        minute = [[overdate substringWithRange:NSMakeRange(, )] intValue];

        second = [[overdate substringWithRange:NSMakeRange(, )] 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:];

    NSString *t = [NSString stringWithFormat:@"%d", [d day]];

    NSString *h = [NSString stringWithFormat:@"%d", [d hour]];

    NSString *fen = [NSString stringWithFormat:@"%d", [d minute]];

    if([d minute] < ) {

        fen = [NSString stringWithFormat:@"0%d",[d minute]];

    }

    NSString *miao = [NSString stringWithFormat:@"%d", [d second]];

    if([d second] < ) {

        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] > ) {

        //计时尚未结束，do_something

//        [_longtime setText:[NSString stringWithFormat:@"%@:%@:%@",d,fen,miao]];

    } else if([d second] == ) {

        //计时结束 do_something

    } else{

//计时器失效

        [theTimer invalidate];

    }

}