my.xml

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

    <fragment
        android:id="@+id/ux_fragment"
        android:name="com.google.ar.sceneform.ux.ArFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <TextView
        android:id="@+id/tvDistance"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:background="@android:color/black"
        android:gravity="center"
        android:padding="8dp"
        android:textColor="@android:color/white"
        android:textSize="20sp" />

</FrameLayout>