First, create a layout named home_content.xml, add FrameLayout, and add an id name. Here is the code for this XML file (you can see the full version on GitHub):

<?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"
        xmlns:tools="http://schemas.android.com/tools"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".ui.MainActivity">
    <android.support.constraint.ConstraintLayout 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"
                                                 tools:context=".ui.MainActivity">

      ----
----

        <android.support.v7.widget.RecyclerView
                android:id="@+id/displayList"
                android:layout_width="0dp"
                android:layout_height="0dp"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                tools:listitem="@layout/post_item"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintHorizontal_bias="0.0" android:layout_marginTop="8dp"
                app:layout_constraintTop_toBottomOf="@+id/appBarLayout"/>

    </android.support.constraint.ConstraintLayout>


    <android.support.design.widget.FloatingActionButton
            android:id="@+id/fabMain"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom|end"
            android:layout_margin="@dimen/fab_margin"
            app:srcCompat="@android:drawable/ic_dialog_email"/>
</android.support.design.widget.CoordinatorLayout>