MDC-Android color in custom views

mdc_color_custom_views.xml

<!-- Copyright 2020 Google LLC.
   SPDX-License-Identifier: Apache-2.0 -->

<!-- In res/values/attrs.xml -->
<declare-styleable name="AppCustomView">
    <attr name="backgroundTint" />
    <attr name="titleTextColor" />
    ...
</declare-styleable>

<!-- In res/values/styles.xml -->
<style name="Widget.App.CustomView" parent="android:Widget">
    <item name="backgroundTint">?attr/colorSurface</item>
    <item name="titleTextColor">
        @color/material_on_surface_emphasis_high_type
    </item>
    ...
</style>