conversations-classic/src/main/res/layout/fragment_conversations_overview.xml

<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <android.support.design.widget.CoordinatorLayout
        android:background="?attr/color_background_primary"
        android:layout_width="match_parent"
        android:layout_height="match_parent">


        <android.support.v7.widget.RecyclerView
            android:id="@+id/list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="?attr/color_background_primary"
           />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="end|bottom"
            android:layout_margin="16dp"
            android:src="@drawable/ic_chat_white_24dp"/>
    </android.support.design.widget.CoordinatorLayout>
</layout>