iOS GCD倒计时

Posted 2022-01-08 qqcc1388

GCD倒计时的好处在于不用考虑是否定时器无法释放的问题，runloop的问题，还有精度更加高
使用GCD创建定时器方法

-(void)startCountDown:(NSInteger)maxTime
    __block int time = 0;
    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);
    //如果有需要可以将定时器保存为全局变量
    _timer = timer;
    dispatch_source_set_timer(timer, DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC, 0 * NSEC_PER_SEC);
    dispatch_source_set_event_handler(timer, ^
        if (time >= maxTime)   //时间到了
            //清空计数
            time = 0;
            //时间到了关闭定时器
            dispatch_source_cancel(timer)
            dispatch_async(dispatch_get_main_queue(), ^
                //在这里执行你要的操作
                do something...
            );
        else
            time++;
        
    );
    dispatch_resume(timer);