本文共 2007 字，大约阅读时间需要 6 分钟。
方法1：使用GCD来实现//倒计时-(void)countdown{ __block int timeout=60; //倒计时时间 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); dispatch_source_set_timer(_timer,dispatch_walltime(NULL, 0),1.0*NSEC_PER_SEC, 0); //每秒执行 dispatch_source_set_event_handler(_timer, ^{ if(timeout<=0){ //倒计时结束，关闭 dispatch_source_cancel(_timer); dispatch_async(dispatch_get_main_queue(), ^{ //设置界面的按钮显示 根据自己需求设置 [_verificationButton setTitle:@"发送验证码" forState:UIControlStateNormal]; _verificationButton.backgroundColor = [UIColor colorWithHexString:@"ec611e"]; _verificationButton.userInteractionEnabled = YES; }); }else{ // int minutes = timeout / 60; int seconds = timeout % 61; NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds]; dispatch_async(dispatch_get_main_queue(), ^{ //设置界面的按钮显示 根据自己需求设置 NSLog(@"____%@",strTime); [_verificationButton setTitle:[NSString stringWithFormat:@"%@S",strTime] forState:UIControlStateNormal]; _verificationButton.userInteractionEnabled = NO; _verificationButton.backgroundColor = [UIColor colorWithRed:203/255.0 green:203/255.0 blue:203/255.0 alpha:1]; }); timeout--; } }); dispatch_resume(_timer);} 方法1：使用NSTimer来实现
主要使用的是NSTimer的scheduledTimerWithTimeInterval方法来每1秒执行一次timeFireMethod函数，timeFireMethod进行倒计时的一些操作，完成时把timer给invalidate掉就可以了，代码如下：
secondsCountDown = 60;//60秒倒计时 countDownTimer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timeFireMethod) userInfo:nil repeats:YES]; -(void)timeFireMethod{ secondsCountDown--; if(secondsCountDown==0){ [countDownTimer invalidate]; } } 转载地址：http://mwtmi.baihongyu.com/