ring-android/app/src/main/res/layout/frag_scan.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"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/error_msg_txt"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="?attr/colorError"
        android:gravity="center_vertical|center_horizontal"
        android:padding="16dp"
        android:textColor="?attr/colorOnError"
        android:textSize="14sp"
        tools:visibility="gone" />

    <com.journeyapps.barcodescanner.DecoratedBarcodeView
        android:id="@+id/barcode_scanner"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center_horizontal"/>

</FrameLayout>