android_mobile_linkdiay/app/src/main/res/layout/activity_preview.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/fl_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/white"
    >

</RelativeLayout>