iOS倒计时控件

/*

 1、继承自UILabel，基本用法与UILabel相同，在UILabel的基础上添加了倒计时功能

 2、时间格式为（分：秒）均显示两位数字，00:00

 3、调用- (void)startCountdown:(NSTimeInterval)timeCount方法，设置倒计时总秒数，开始倒计时

 4、通过属性timeOutBlock，获得倒计时结束的回调

 */

@interface CountdownTimerLabel : UILabel

/*

 倒计时结束回调

 */

@property(nonatomic, copy) dispatch_block_t timeOutBlock;

/*

 开始倒计时

 */

- (void)startCountdown:(NSTimeInterval)timeCount;

@end


@interface CountdownTimerLabel() {



    dispatch_source_t timer;

    NSInteger timeRemaining;

}

@end

@implementation CountdownTimerLabel



- (void)startCountdown:(NSTimeInterval)timeCount {

    [self showCountdown];

    __weaktypeof(self) weakSelf =self;

    timeRemaining= timeCount;

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_TARGET_QUEUE_DEFAULT, 0);

    timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);

    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 0);

    dispatch_source_set_event_handler(timer, ^{

        if(self->timeRemaining<=0) {

            dispatch_source_cancel(self->timer);

            dispatch_async(dispatch_get_main_queue(), ^{

                [weakSelf timeOut];

            });

        }else{

            dispatch_async(dispatch_get_main_queue(), ^{

                self->timeRemaining--;

                [weakSelf showCountdown];

            });

        }

    });

    dispatch_resume(timer);

}

- (void)showCountdown {



    NSInteger minutes =floor(timeRemaining/60);

    NSInteger seconds =trunc(timeRemaining- minutes *60);

    self.text= [NSString stringWithFormat:@"%02ld:%02ld",minutes,seconds];

}

- (void)timeOut {

    if (_timeOutBlock) {

        _timeOutBlock();

    }

}

- (void)dealloc {

    if(timer) {

        dispatch_source_cancel(timer);

        timer=nil;

    }

}