ring-android/app/src/main/res/layout/frag_qrcode.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:clickable="true"
    android:background="@color/black">

    <ImageButton
        android:id="@+id/exit"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="20dp"
        android:layout_marginRight="20dp"
        android:background="@null"
        android:src="@drawable/ic_action_remove" />

    <ImageView
        android:id="@+id/qr_image"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerHorizontal="true"
        android:layout_centerInParent="true"
        android:background="@null" />

</RelativeLayout>