<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@color/accent_alpha_20" android:state_focused="true" />
  <item android:drawable="@color/accent_alpha_20" android:state_pressed="true" />
  <item android:drawable="@color/accent_alpha_20" android:state_selected="true" />
  <item android:drawable="@color/primary" />
</selector>

<!--
Highlights the background on focus/press/select. In API 21+ this is unused
in favor of a ripple effect (see drawable-v21/button_selector.xml).
-->
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@color/accent_alpha_20" android:state_focused="true" />
  <item android:drawable="@color/accent_alpha_20" android:state_pressed="true" />
  <item android:drawable="@color/accent_alpha_20" android:state_selected="true" />
  <item android:drawable="@color/primary" />
</selector>

Clarify default button selector usage
Clarify default button selector usage
