//启动一个定时器
self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(operatePerSecond) userInfo:nil repeats:YES];
 
//实现定时器中的方法
- (void)operatePerSecond {
    if (time == 1) {
      [self.timer invalidate];
      time = 60;
      [self.codeButton setTitle:@"重新获取" forState:UIControlStateNormal];
      self.codeButton.tintColor = [UIColor blackColor];
      self.codeButton.enabled = YES;
    }else {
      time --;
      [self.codeButton setTitle:[NSString stringWithFormat:@"%ds" ,time] forState:UIControlStateNormal];
    }
}

3.此时主要逻辑已经完成，但要记得：在本页面即将消失的时候也要停掉计时器self.timer。

二、利用GCD实现

1.定义一个用于计时的time（此时要用block修饰）---  block int time = 60;

  //倒计时时间
  __block int timeout = 60;
  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_TIME_NOW, 1.0 * NSEC_PER_SEC, 0 * NSEC_PER_SEC);
  dispatch_source_set_event_handler(timer, ^{
    if(timeout == 1){
      //倒计时结束，关闭
      dispatch_source_cancel(timer);
      dispatch_async(dispatch_get_main_queue(), ^{
      timeout = 60;
      [self.codeButton setTitle:@"重新获取" forState:UIControlStateNormal];
      self.codeButton.tintColor = [UIColor blackColor];
      self.codeButton.enabled = YES;
      });
    }else{
      NSString *strTime = [NSString stringWithFormat:@"%ds",timeout];
      dispatch_async(dispatch_get_main_queue(), ^{
        [self.codeButton setTitle:strTime forState:UIControlStateNormal];
      });
      timeout--;
    }
  });
dispatch_resume(timer);

2.把上述代码写入点击方法中即可实现倒计时效果。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。