<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- Non focused states -->
    <item android:drawable="@drawable/button" 
        android:state_focused="false" 
        android:state_pressed="false" 
        android:state_selected="false"/>
    <!-- Pressed -->
    <item android:drawable="@drawable/button_pressed" 
        android:state_focused="false" 
        android:state_pressed="true" 
        android:state_selected="false"/>

</selector>