res/drawable/action_card_background.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  ~ Copyright (C) 2015 The Android Open Source Project
  ~
  ~ Licensed under the Apache License, Version 2.0 (the "License");
  ~ you may not use this file except in compliance with the License.
  ~ You may obtain a copy of the License at
  ~
  ~      http://www.apache.org/licenses/LICENSE-2.0
  ~
  ~ Unless required by applicable law or agreed to in writing, software
  ~ distributed under the License is distributed on an "AS IS" BASIS,
  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  ~ See the License for the specific language governing permissions and
  ~ limitations under the License.
  -->
<selector xmlns:android="http://schemas.android.com/apk/res/android"
    android:enterFadeDuration="@android:integer/config_shortAnimTime"
    android:exitFadeDuration="@android:integer/config_shortAnimTime">

    <item android:state_focused="true">
      <shape>
          <solid android:color="@color/action_card_selected_background"/>
          <corners android:radius="2dp" />
      </shape>
    </item>

    <item android:state_focused="false">
      <shape>
          <solid android:color="@color/action_card_deselected_background"/>
          <corners android:radius="2dp" />
      </shape>
    </item>

</selector>