Android Master/Detail - have FAB anchored to master on single or multi pane

Question

I would like a Floating Action Button (FAB) to be anchored to the master pane when showing two panes on a tablet like the Gmail app does (see attached image) but have been unable to code this functionality using the Master/Detail template in Android Studio.

The default behavior is to have the FAB display on the bottom/right of the screen in both single or multi-pane mode.

I've tried moving the FAB from the activity_item_list.xml to the layouts containing the RecyclerView but that causes the detail pane to not be displayed in multi-pane mode.

Is it possible to have the FAB also display anchored to the master using the layouts from the master-detail template or is it necessary to start from scratch and perhaps use multiple fragments and activities?

Below is the altered layout for the item_list now containing the FAB. I added a RelativeLayout and the FAB over what was originally in the template.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginLeft="16dp"
    android:layout_marginRight="16dp"
    android:baselineAligned="false"
    android:divider="?android:attr/dividerHorizontal"
    android:orientation="horizontal"
    android:showDividers="middle"
    tools:context=".ItemListActivity">

    <!-- This layout is a two-pane layout for the Items master/detail flow.-->

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:id="@+id/item_list"
            android:name=".ItemListFragment"
            android:layout_width="@dimen/item_width"
            android:layout_height="match_parent"
            android:layout_marginLeft="16dp"
            android:layout_marginRight="16dp"
            app:layoutManager="LinearLayoutManager"
            tools:context=".ItemListActivity"
            tools:listitem="@layout/item_list_content" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_margin="@dimen/fab_margin"
            android:layout_alignParentRight="true"
            android:layout_alignParentBottom="true"
            android:src="@android:drawable/ic_dialog_email" />
    </RelativeLayout>

    <FrameLayout
        android:id="@+id/item_detail_container"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="3" />

</LinearLayout>

Answer 1

The issue was the layout. Adding a 2nd relative layout and placing the detail to the right of the master solved the issue.

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginLeft="16dp"
    android:layout_marginRight="16dp"
    android:baselineAligned="false"
    android:divider="?android:attr/dividerHorizontal"
    android:orientation="horizontal"
    android:showDividers="middle"
    tools:context=".ItemListActivity">

    <!--This layout is a two-pane layout for the Items master/detail flow.-->
    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent">

    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:id="@+id/item_list_master">

        <android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:id="@+id/item_list"
            android:name=".ItemListFragment"
            android:layout_width="@dimen/item_width"
            android:layout_height="match_parent"
            android:layout_marginLeft="16dp"
            android:layout_marginRight="16dp"
            app:layoutManager="LinearLayoutManager"
            tools:context=".ItemListActivity"
            tools:listitem="@layout/item_list_content" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_margin="@dimen/fab_margin"
            android:layout_alignRight="@id/item_list"
            android:src="@android:drawable/ic_dialog_email" />

    </RelativeLayout>
        <FrameLayout
            android:id="@+id/item_detail_container"
            android:layout_width="400dp"
            android:layout_height="match_parent"
            android:layout_toRightOf="@+id/item_list_master"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true" />

    </RelativeLayout>
</LinearLayout>