tachiyomi/app/src/main/res/layout/categories_controller.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
             xmlns:tools="http://schemas.android.com/tools"
             xmlns:app="http://schemas.android.com/apk/res-auto"
             android:layout_width="match_parent"
             android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/recycler"
        android:choiceMode="multipleChoice"
        tools:listitem="@layout/categories_item"
        />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        app:layout_anchor="@id/recycler"
        app:srcCompat="@drawable/ic_add_white_24dp"
        style="@style/Theme.Widget.FAB"/>

</FrameLayout>