res/layout/floating_split_select_view.xml

<?xml version="1.0" encoding="utf-8"?>
<com.android.quickstep.views.FloatingTaskView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

    <com.android.quickstep.views.SplitPlaceholderView
        android:id="@+id/split_placeholder"
        android:layout_width="match_parent"
        android:layout_height="@dimen/split_placeholder_size"
        android:background="?android:colorPrimary"
        android:visibility="gone" />

</com.android.quickstep.views.FloatingTaskView>