title: MediaController BACK button not work
body: <p>I have a music app with <code>MediaPayer</code> and <code>MediaController</code> and when music play and i hit back button can't let the activity exit.
  I found from source code that <code>MediaController</code> capture the <code>KeyEvent.KEYCODE_BACK</code> in <code>MediaController#dispatchKeyEvent()</code>. so I override the method by adding following code:</p>
  
  <pre><code>if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
      return false;
  }
  return super.dispatchKeyEvent(event);
  </code></pre>
  
  <p>But it still no luck.</p>