How does "?android:attr/activatedBackgroundIndicator" work?
<p>I was looking for how to highlight a selected item in a list when displaying a contextual action bar for the selection, and the solution I found was to set the <code>android:background</code> attribute of my row layout xml to <code>"?android:attr/activatedBackgroundIndicator"</code>.</p>

<p>How does setting this work though?</p>

<ol>
<li>what is the mechanism involved?</li>
<li>what do the syntax elements like "?", "attr", "activatedBackgroundIndicator" mean?</li>
<li>where is the meaning of "activatedBackgroundIndicator" defined?</li>
</ol>
