res/drawable/button_ripple.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
/**
 * Copyright (C) 2017 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">
    <item android:state_focused="true" android:drawable="@color/gray_button_focused"/>
    <item android:state_enabled="true">
    <ripple android:color="@color/gray_button_focused">
        <item>
            <shape>
                <solid android:color="@color/gray"/>
                <corners android:radius="@dimen/button_corner_radius"/>
            </shape>
        </item>
    </ripple>
    </item>
    <item>
        <shape>
            <solid android:color="@color/gray_button_focused"/>
            <corners android:radius="@dimen/button_corner_radius"/>
        </shape>
    </item>
</selector>