webview와 imageview를 FrameLayout 안에, 중복 배치하면 되는거 아닌가요? 굳이 복잡하게 할 이유가 없을 듯 한데요..
ex)
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="
http://schemas.android.com/apk/res/android"
android:layout_gravity="center">
<WebView
android:id="@+id/webview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center" />
<ImageView
android:id="@+id/ImageView01"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center">
</FrameLayout>
http://kimg0130.tistory.com/entry/FrameLayout-%EC%A4%91%EC%B2%A9%EB%B0%B0%EC%B9%98