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添加到 单利类 或者button分类理都可以

返回之后再重新进来按钮倒计时会重置 不会在后台继续

/**
 *  倒计时按钮
 *
 *  @param timeLine 倒计时总时间
 *  @param title    还没倒计时的title 结束时的
 *  @param subTitle 倒计时中的子名字，如时、分
 *  @param mColor   还没倒计时的颜色
 *  @param color    倒计时中的颜色
 *  @param button   要操作的按钮
 */
- (void)startWithTime:(NSInteger)timeLine title:(NSString *)title countDownTitle:(NSString *)subTitle mainColor:(UIColor *)mColor countColor:(UIColor *)color disposeButton:(UIButton *)button{
    
    
    //倒计时时间
    __block NSInteger timeOut = timeLine;
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    //每秒执行一次
    dispatch_source_set_timer(_timer, dispatch_walltime(NULL, 0), 1.0 * NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler(_timer, ^{
        
        //倒计时结束，关闭
        if (timeOut <= 0) {
            dispatch_source_cancel(_timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                button.backgroundColor = mColor;
                [button setTitle:title forState:UIControlStateNormal];
                button.userInteractionEnabled = YES;
            });
        } else {
            int allTime = (int)timeLine + 1;
            int seconds = timeOut % allTime;
            NSString *timeStr = [NSString stringWithFormat:@"%0.2d", seconds];
            dispatch_async(dispatch_get_main_queue(), ^{
                button.backgroundColor = color;
                [button setTitle:[NSString stringWithFormat:@"%@%@",timeStr,subTitle] forState:UIControlStateNormal];
                button.userInteractionEnabled = NO;
            });
            timeOut--;
        }
    });
    dispatch_resume(_timer);
}

#pragma mark -  倒计时按钮 跳转页面不重置时间 (返回的话还会重置)

+ (void)startSeniorWithTime:(NSInteger)timeLine
                      title:(NSString *)title
             countDownTitle:(NSString *)subTitle
                  mainColor:(UIColor *)mColor
                 countColor:(UIColor *)color
              disposeButton:(UIButton *)button {

    int __block time = (int) timeLine;

    button.enabled = NO;
    //获取系统全局队列
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    //基于全局队列创建定时器
    dispatch_source_t timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
    //设置定时器为点击后马上开始，间隔时间为1秒，没有延迟
    dispatch_source_set_timer(timer, dispatch_time(DISPATCH_TIME_NOW, 0), 1 * NSEC_PER_SEC, 0);
    dispatch_source_set_event_handler(timer, ^{
        if (time == 0) {
            button.enabled = YES;
            dispatch_source_cancel(timer);
            dispatch_async(dispatch_get_main_queue(), ^{
                button.backgroundColor = mColor;
                [button setTitle:title forState:UIControlStateNormal];
                button.userInteractionEnabled = YES;
            });
        } else {
            time--;
            NSString *string = [NSString stringWithFormat:@"%d%@", time, subTitle];
            dispatch_async(dispatch_get_main_queue(), ^{
                button.backgroundColor = color;
                [button setTitle:[NSString stringWithFormat:@"%@", string] forState:UIControlStateNormal];
                button.userInteractionEnabled = NO;
            });
        }
    });

    dispatch_resume(timer);
}

干货代码 我的一个纯代码的基础框架有各种常用的分类封装入手即用