【IOS】倒计时实现的两种方法

1 secondsCountDown = 60;//60秒倒计时
2 countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES];
3 -(void)timeFireMethod{
4     secondsCountDown--;
5     if(secondsCountDown==0){
6       [countDownTimer invalidate];
7     }
8 }

 1     __block int timeout=300; //倒计时时间
 2     dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
 3     dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0,queue);
 4     dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行
 5     dispatch_source_set_event_handler(_timer, ^{
 6         if(timeout<=0){ //倒计时结束，关闭
 7             dispatch_source_cancel(_timer);
 8             dispatch_release(_timer);
 9             dispatch_async(dispatch_get_main_queue(), ^{
10         //设置界面的按钮显示 根据自己需求设置
11                 。。。。。。。。
12             });
13         }else{
14             int minutes = timeout / 60;
15             int seconds = timeout % 60;
16             NSString *strTime = [NSString stringWithFormat:@"%d分%.2d秒后重新获取验证码",minutes, seconds];
17             dispatch_async(dispatch_get_main_queue(), ^{
18                 //设置界面的按钮显示 根据自己需求设置
19         。。。。。。。。
20             });
21             timeout--;
22             
23         }
24     });
25     dispatch_resume(_timer);