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

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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">

    <FrameLayout
        android:id="@+id/camera_preview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/button_capture"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:contentDescription="@string/action_call_decline"
        android:padding="16dp"
        app:backgroundTint="@color/holo_green_dark"
        app:rippleColor="@android:color/white"
        app:srcCompat="@drawable/ic_photo_camera"
        app:useCompatPadding="true" />
</RelativeLayout>