title: Android expandablelistview group/parent background image change when collapse or expand
body: <p>I try to swap expandablelistview group background image when it is collapse or expand. But the background image was not correctly swap. For example when I expand the first group, background of second or third group get swapped.</p>
  
  <p>I am using RelativeLayout (group layout) and SimpleExpandableListAdapter (adapter). Here is what I did:</p>
  
  <pre><code>// Create 2 drawable background. One for collapse and one for expand
  private Drawable collapseBG, expandBG;
  private ExpandableListView myView;
  
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
      collapseBG = getResources().getDrawable(R.drawable.box_bg_header_collapse);
      expandBG = getResources().getDrawable(R.drawable.box_bg_header_expand);
      myView = (ExpandableListView) findViewById(R.id.myView);
  }
  
  myView.setOnGroupCollapseListener(new ExpandableListView.OnGroupCollapseListener() {
      public void onGroupCollapse(int groupPosition_c) {
          myView.getChildAt(groupPosition_c).setBackgroundDrawable(collapseBG);
      }
  });
  
  myView.setOnGroupExpandListener (new ExpandableListView.OnGroupExpandListener() {
      public void onGroupExpand(int groupPosition_e) {
          myView.getChildAt(groupPosition_e).setBackgroundDrawable(expandBG);
      }
  });
  </code></pre>
  
  <p>Is anyone know how to make this works?</p>