iOS 更新Button title 闪动解决

#pragma mark 获取验证码倒计时

-(void)countDown{i

         _secondsCountDown=60;

         [_captchaBtn setHighlighted:NO];

         _countDownTimer=[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateCodeBtn) userInfo:nil repeats:YES];

}

-(void)updateCodeBtn {

         if(_secondsCountDown>=0){

                //重要的是这一句 设置Button 的titleLabel text属性

                 _captchaBtn.titleLabel.text = [NSString stringWithFormat:@"%ds",_secondsCountDown];

                 //并且title也要设置

                 [_captchaBtn setTitle:[NSString stringWithFormat:@"%ds",_secondsCountDown]forState:UIControlStateNormal];

                 _secondsCountDown--;

       }else{

                [_captchaBtn setTitle:@"获取验证码" forState:UIControlStateNormal];

                _countDownTimer=nil;

                [_captchaBtn setEnabled:YES];

       }

}