tests/DirectRenderingClusterSample/res/drawable/btn_nav.xml

<?xml version="1.0" encoding="UTF-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_focused="true" >
        <layer-list>
            <item android:drawable="@drawable/ic_nav"/>
            <item android:drawable="@drawable/focused_button_shape"/>
        </layer-list>
    </item>
    <item android:drawable="@drawable/ic_nav"/>
</selector>