title: Change expandable indicator in ExpandableListView
body: <p>Trying to create an ExpandableListView. The initial view with the groups shows up fine. However, when I click the list item, my arrow does not change. See the images below.</p>
  
  <p><img src="https://i.stack.imgur.com/nxBbY.png" alt="enter image description here"> </p>
  
  <p>How can I change the arrow's direction?</p>
  
  <p>The layout XML:</p>
  
  <pre><code>  &lt;ExpandableListView
          android:id="@+id/expandable_list"
          android:layout_width="fill_parent"
          android:layout_height="match_parent"            
          android:divider="@null"
          android:background="#ffffff"
          android:groupIndicator="@drawable/settings_selector"
          android:transcriptMode="alwaysScroll" /&gt;
  </code></pre>
  
  <p><strong>settings_selector.xml</strong>:</p>
  
  <pre><code> &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;animation-list xmlns:android="http://schemas.android.com/apk/res/android" &gt;
  
  &lt;selector xmlns:android="http://schemas.android.com/apk/res/android" &gt;
      &lt;item
          android:drawable="@drawable/arrow_down"
          android:state_empty="true"/&gt;
      &lt;item
          android:drawable="@drawable/arrow_right"
          android:state_expanded="true"/&gt;
  &lt;/selector&gt;
  
  &lt;/animation-list&gt;
  </code></pre>