Here's one we did for an app:
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/ic_bcnav_ebilling_focus"
android:state_checked="true" />
<item android:drawable="@drawable/ic_bcnav_ebilling_focus"
android:state_selected="true" />
<item android:drawable="@drawable/ic_bcnav_ebilling_focus"
android:state_pressed="true" />
<item android:drawable="@drawable/ic_bcnav_ebilling_focus"
android:state_focused="true" />
<item android:drawable="@drawable/ic_bcnav_ebilling" />
</selector>
Each state has a different drawable, although in this example, we don't really care about all states being very different - just focus=true get a highlighted drawable (it has "..._focus")