title: Custom group expanding icon in ExpandableListView
body: <p><img src="https://i.stack.imgur.com/wf81S.png" alt="enter image description here"></p>
  
  <p>I am trying to use a custom icon for group expand and collapse state of an ExpandableListView. But this doesn't seem to work. The icons doesn't get changed even when the Output messages are working sequentially.</p>
  
  <pre><code>    explistView.setOnGroupClickListener(new OnGroupClickListener()
      {
          @Override
          public boolean onGroupClick(ExpandableListView parent, View v, int groupPosition, long id)
          {
              groupIndicator = (ImageView) findViewById(R.id.group_indicator);
              if (parent.isGroupExpanded(groupPosition))
              {
                  System.out.println("1");
                  parent.collapseGroup(groupPosition);
                  System.out.println("2");
                  groupIndicator.setImageResource(R.drawable.expand_icon_35x35);
                  System.out.println("3");
                  adapter.notifyDataSetChanged();
              } 
              else
              {
                  System.out.println("4");
                  parent.expandGroup(groupPosition);
                  System.out.println("5");
                  groupIndicator.setImageResource(R.drawable.collapse_icon_35x35);
                  System.out.println("6");
                  adapter.notifyDataSetChanged();
              }
              return true;
          }
      });
  </code></pre>