app/src/main/res/values/activityStyle.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="activityStyle">
<item name="android:background">?attr/colorPrimaryVariant</item>
<item name="android:layout_height">match_parent</item>
<item name="android:layout_width">match_parent</item>
</style>
</resources>