Signal-Android/app/src/main/res/layout/activity_mediapreview_v2.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">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragment_container_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@color/signal_dark_colorNeutral" />

    <ImageView
        android:id="@+id/transition_image_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:adjustViewBounds="true"
        android:importantForAccessibility="no"
        android:transitionName="thumb" />

</FrameLayout>