@Justin Pollard xml code works really good. As a side note you can add a ripple effect with the following xml lines.
<item>
<ripple
xmlns:android="http://schemas.android.com/apk/res/android"
android:color="?android:colorControlHighlight" >
<item android:id="@android:id/mask">
<shape android:shape="oval" >
<solid android:color="#FFBB00" />
</shape>
</item>
<item>
<shape android:shape="oval" >
<solid android:color="@color/ColorPrimary" />
</shape>
</item>
</ripple>
</item>