samples/VirtualDeviceManager/host/res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:orientation="vertical">

    <androidx.appcompat.widget.Toolbar
        android:id="@+id/main_tool_bar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:elevation="4dp"
        android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <androidx.fragment.app.FragmentContainerView
            android:id="@+id/connectivity_fragment_container"
            android:name="com.example.android.vdmdemo.common.ConnectivityFragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center_horizontal"
            android:orientation="horizontal">

            <Button
                android:id="@+id/create_home_display"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:onClick="onCreateHomeDisplay"
                android:text="@string/create_home_display" />

            <Button
                android:id="@+id/create_mirror_display"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:onClick="onCreateMirrorDisplay"
                android:text="@string/create_mirror_display" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:gravity="center_horizontal"
            android:orientation="horizontal">

            <Button
                android:id="@+id/create_desktop_display"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:onClick="onCreateDesktopDisplay"
                android:text="@string/create_desktop_display" />
        </LinearLayout>

        <include layout="@layout/custom_launcher" />

    </LinearLayout>

</LinearLayout>