CoordinateLayout app:layout_anchor and app:layout_anchorGravity not working in fragments

Question

I'm using CoordinateLayout in fragment's layout file. There I need to use FloatingActionButton or ImageButton between two layouts. I got sample code from this answer.

I created two fragments with two same layout file. fragment1.xml, fragment2.xml

<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <LinearLayout
        android:id="@+id/viewA"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="0.4"
        android:background="@android:color/holo_purple"
        android:orientation="horizontal"/>

    <LinearLayout
        android:id="@+id/viewB"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_weight="0.6"
        android:background="@android:color/holo_orange_light"
        android:orientation="horizontal"/>

</LinearLayout>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_margin="16dp"
    android:clickable="true"
    android:src="@drawable/icon_add_new"
    app:layout_anchor="@id/viewA"
    app:layout_anchorGravity="bottom|right|end"/>

</android.support.design.widget.CoordinatorLayout>

When I run the app fragment1 will show then after the button click fragment2 will show. But when replacing first fragment with second fragment the button position get changed to top left corner like below.

fragment 1

fragment 2

I can't understand why? Anyone can help me?