多线程创建计时器Timer

（1）计时器， 使用多线程建立，以及释放

• (void)viewDidLoad{
  [self createTimer];
  }

• (void)dealloc
  {
  [self deallocTimer];
  }

// 返回之后，停止计时器

• (void)deallocTimer{
  if (self.myTimer != nil) {
  dispatch_source_cancel(self.myTimer);
  self.myTimer = nil;
  }
  }

• (void)createTimer{

  __block NSInteger time = 5; //倒计时时间
  self.timeInteger = time;
  dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
  self.myTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);

  dispatch_source_set_timer(self.myTimer, DISPATCH_TIME_NOW, 1.0*NSEC_PER_SEC, 0); //每秒执行
  dispatch_resume(self.myTimer);

  dispatch_source_set_event_handler(self.myTimer, ^{

    if(time <= 0){ //倒计时结束，关闭
        
        dispatch_source_cancel(self.myTimer);
        
        dispatch_async(dispatch_get_main_queue(), ^{
            self.bottomButton.enabled = YES;
            // 改变底部view的背景颜色
            self.bottomButton.backgroundColor = [UIColor colorWithHexString:@"#FF6868"];
            [self.bottomButton setTitle:@"我已阅读并同意条款" forState:UIControlStateNormal];
            [self.bottomButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];
        });
    } else{
        NSLog(@"我已阅读并同意条款（%d秒）", time);
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.bottomButton setTitle:[NSString stringWithFormat:@"我已阅读并同意条款（%d秒）", time] forState:UIControlStateNormal];
            time --;
        });
    }
  

  });
  }