title: How to keep Android app running and quit Unity Activity
body: <p>I'm developing an app that integrates with Unity3d, in some part of my code I call an UnityPlayerActivity that starts the Unity3d code. When user finishes using the Unity3d he press a button and go back to Android code. 
  My problem is when I go back to android code, after UnityPlayerActivity calls: </p>
  
  <pre><code>@Override protected void onDestroy ()
  {
      mUnityPlayer.quit();
      super.onDestroy();
  }
  </code></pre>
  
  <p>The application is closed, not only the Unity Activity. I could not call this method, but I think that would be wasting memory.</p>
  
  <p>Is there any way I could quit only Unity3d activity and keep my application running normally so I could start Unity3d part again another time?</p>
  
  <p>Tks</p>