session-android/res/layout/transfer_controls_view.xml

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
       xmlns:app="http://schemas.android.com/apk/res-auto">

    <com.pnikosis.materialishprogress.ProgressWheel
            android:id="@+id/progress_wheel"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@drawable/progress_background"
            android:visibility="gone"
            app:matProg_barColor="@color/white"
            app:matProg_linearProgress="true"
            app:matProg_spinSpeed="0.333" />

    <ImageButton android:id="@+id/download_button"
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
                 android:layout_gravity="center"
                 android:background="@drawable/progress_background"
                 android:src="@drawable/ic_file_download_white_36dp"
                 android:visibility="gone" />
</merge>