activity.xml

<FrameLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
  
  <!--Below FrameLayout doesn't need to be a FrameLayout. Any ViewGroup will do -->
  <FrameLayout
    android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    ...other attrs go here
    android:visibility="gone">
    <!--Content Views go here -->
  </FrameLayout>
  
  <WebView
    android:id="@+id/splash"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />
    
</FrameLayout>