floating action button unexpected anchor gravity change

Question

I've got an activity and several fragments. One of the fragments contains FAB with an anchor gravity bottom|right|end. It looks good, but when I start another fragment and then press back button my FAB appears at the top left corner. I use Coordinator layout but it doesn't help. Here is my layout:

<?xml version="1.0" encoding="utf-8"?>
<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 xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:id="@+id/fragment_main_page">

<ListView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/main_page_listview"
    android:layout_marginTop="5dp">

</ListView>

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_marginTop="3dp">

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="12dp"
        android:src="@drawable/info_main_page"
        android:layout_gravity="center_vertical"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:layout_gravity="center_vertical"
        android:id="@+id/how_to_use"
        android:text="@string/how_to_use"
        android:textAllCaps="false"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:textStyle="italic"
        android:background="@android:color/transparent"/>

</LinearLayout>

</LinearLayout>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/floating_promos"
    android:layout_width="42dp"
    android:layout_height="42dp"
    android:layout_margin="16dp"
    android:clickable="true"
    android:src="@drawable/floating_promos"
    app:layout_anchor="@id/fragment_main_page"
    app:layout_anchorGravity="bottom|right|end"
    app:backgroundTint="#fb9f12"
    app:fabSize="mini"/>
   </android.support.design.widget.CoordinatorLayout>

Answer 1

I did a small tweak to make it work as I needed I simply added the listener to check if the recycler view is updated and made changes to FAB inside it. Hope this will help you.

listWorkData.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
    @Override
    public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
        listWorkData.removeOnLayoutChangeListener(this);

        CoordinatorLayout.LayoutParams lp = (CoordinatorLayout.LayoutParams) btnSubmitConfirm.getLayoutParams();
        lp.anchorGravity = Gravity.BOTTOM | GravityCompat.END;
        btnSubmitConfirm.setLayoutParams(lp);
    }
});

listWorkData.getAdapter().notifyDataSetChanged();