title: android: How to set a listener that fires when my ViewFlipper shows a new child
body: <p>I have a ViewFlipper for which I want a listener to fire when the child displayed is changed.  I have set an OnFocusChangeListener to the ViewFlipper but it never fires when I flip from child 0 to child 1 or vice-versa.  The ViewFlipper contains two RelativeLayouts and I have tried setting OnFocusChangeListeners for those but I get a ClassCastException when I try to set it.  Here's my code:</p>
  
  <pre><code>RelativeLayout songsLayout = (RelativeLayout) findViewById(R.id.song_page_layout);
  songsLayout.setOnFocusChangeListener(new OnFocusChangeListener() {
      public void onFocusChange(View view, boolean hasFocus) {
          showPopUp("View " + view.getId() + " now has focus: " + hasFocus);
      }       
  } );
  </code></pre>
  
  <p>R.is.song_page_layout is one of my RelativeLayouts and showPopUp() is a function I use to show, well, popups.</p>
  
  <p>Does anyone have working code for some sort of trigger that fires when a ViewFlipper changes which child is displayed?</p>