Android selector needs drawable instead of just background

The following will result in a crash saying that cannot inflate the drawable.

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_pressed="true" android:background="#000000" />
  <item android:state_focused="true" android:background="#000000" />
  <item android:background="#FFFFFF" />
</selector>

The solution is to change the background to use drawable

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:state_pressed="true" android:drawable="@color/grey" />
  <item android:state_focused="true" android:drawable="@color/grey" />
  <item android:drawable="@color/white" />
</selector>

android:drawable attribute does not accept raw color.

Define color.xml in res/values.

<?xml version="1.0" encoding="utf-8"?>
<resources>
     <color name="black">#000</color>
     <color name="white">#fff</color>
     <color name="grey">#cccccc</color>
</resources>