FossifyGallery/app/src/main/res/layout/pager_photo_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/photo_holder"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/gif_holder"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="gone"/>

    <uk.co.senab.photoview.PhotoView
        android:id="@+id/photo_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</RelativeLayout>