title: cocos2dx 3.0 beta2 Button Click function is called twice by one time click
body: <p>The following is my code:</p>
  
  <pre><code>Button* buttonLogin = dynamic_cast&lt;Button*&gt;(m_pLayout-&gt;getChildByName("login_Button"));
  if (buttonLogin)
      buttonLogin-&gt;addTouchEventListener(this,toucheventselector(GameLoginLayer::touchButton));
  </code></pre>
  
  <p>when I debug the app, touchButton function is called twice. It's Weird. There's only one function in own codes will call the button function.</p>
  
  <p>I check the cocostudio original file of UI, only on button was drawn.</p>
  
  <p>Anyone has some suggestion?</p>
  
  <p>Thanks.</p>