session-android/res/layout/camera_controls_portrait.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    android:layout_marginBottom="16dp"
    android:layout_gravity="bottom">

    <Button
        android:id="@+id/camera_capture_button"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:background="@drawable/ic_camera_shutter" />

    <ImageButton
        android:id="@+id/camera_flip_button"
        android:layout_width="48dp"
        android:layout_height="wrap_content"
        android:layout_toStartOf="@+id/camera_capture_button"
        android:layout_marginEnd="40dp"
        android:layout_centerVertical="true"
        android:src="@drawable/ic_switch_camera_36"
        android:scaleType="fitCenter"
        android:background="?selectableItemBackgroundBorderless"
        android:visibility="gone"
        tools:visibility="visible" />

</RelativeLayout>