title: How to correctly use listSeparatorTextViewStyle for ExpadanbleListView header items?
body: <p>I've spent a lot of time looking for a way to get the default header state indicator (▲/▼) to show on my <code>ExpadanbleListView</code> header item (something I would expect to be trivial). Eventually, I've found mention of the <code>android:attr/listSeparatorTextViewStyle</code> style. So I tried this in my group view layout XML:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
      &gt;
  
      &lt;TextView
          style="?android:attr/listSeparatorTextViewStyle"
          android:id="@+id/firmwareItemHeader"
          android:textAppearance="?android:attr/textAppearanceLarge"
          android:layout_width="wrap_content"
          android:layout_height="50dp"/&gt;
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>But the result is wrong - the indicator overlaps with the text: </p>
  
  <p><a href="https://i.stack.imgur.com/vReab.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vReab.png" alt="enter image description here"></a></p>
  
  <p>How to fix this?</p>
  
  <p>Of note: the <code>ExpandableListView</code> has <code>android:indicatorRight="?android:attr/expandableListPreferredChildIndicatorRight"</code>.</p>
  
  <p>As you can see, my header view layout is a primitive single <code>TextView</code>, and it's going to stay that way. I'll happily use a default view with an indicator instead of my own XML, if such a view exists (I couldn't find one).</p>
  
  <p>One can set a custom <code>@drawable</code> indicator via <code>android:groupIndicator</code> attibute of the list view, but again, I can't find any default value.</p>