首先你要创建一个按钮，然后在按钮的点击事件里面写上一下代码即可：

__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);

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(), ^{

[self.getAuthCodeBtn setTitle:@"重新获取" forState:UIControlStateNormal];

self.getAuthCodeBtn.userInteractionEnabled = YES;

self.getAuthCodeBtn.backgroundColor = [UIColor whiteColor];

});

}else{

int seconds = timeout;

NSString *strTime = [NSString stringWithFormat:@"%.2d", seconds];

dispatch_async(dispatch_get_main_queue(), ^{

self.getAuthCodeBtn.userInteractionEnabled = NO;

[UIView beginAnimations:nil context:nil];

[UIView setAnimationDuration:1];

[self.getAuthCodeBtn setTitle:[NSString stringWithFormat:@"%@秒后重新发送",strTime] forState:UIControlStateNormal];

[UIView commitAnimations];

});

timeout--;

}

});

dispatch_resume(_timer);