space-android/res/drawable/btn.xml

<?xml version="1.0" encoding="UTF-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_focused="true" android:state_pressed="true" android:drawable="@drawable/btn_round_pressed" />
  <item android:state_focused="true" android:state_pressed="false" android:drawable="@drawable/btn_round_pressed" />
  <item android:state_focused="false" android:state_pressed="true" android:drawable="@drawable/btn_round_pressed" />
  <item android:state_focused="false" android:state_pressed="true" android:drawable="@drawable/btn_round_pressed" />
  <item android:drawable="@drawable/btn_round"/>
</selector>