iOS 按钮倒计时功能

iOS 按钮倒计时功能， 建议把按钮换成label，这样会避免读秒时闪烁

  __block int time = ;
         __block UIButton *verifybutton = _GetverificationBtn;
         verifybutton.enabled = NO;
         dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, );
         dispatch_source_t _timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, , ,queue);
         dispatch_source_set_timer(_timer,dispatch_walltime(NULL, ),1.0*NSEC_PER_SEC, ); //每秒执行
         dispatch_source_set_event_handler(_timer, ^{
             if(time<=){ //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
                     [verifybutton setTitle:@"获取验证码" forState:UIControlStateNormal];
                     verifybutton.enabled = YES;
                 });
             }else{
                 dispatch_async(dispatch_get_main_queue(), ^{
                     //设置界面的按钮显示 根据自己需求设置
                     verifybutton.backgroundColor = [UIColor grayColor];
                     NSString *strTime = [NSString stringWithFormat:@"获取验证码(%d)",time];
                     [verifybutton setTitle:strTime forState:UIControlStateNormal];
                     verifybutton.titleLabel.textColor = [UIColor whiteColor];
                 });
                 time--;
             }
         });
         dispatch_resume(_timer);