Android Constraint Layout: ConstraintLayout Placeholder

Placeholder

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/endBottom"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="就这" />

    <androidx.constraintlayout.widget.Placeholder
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:content="@+id/endBottom"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"

        />

</androidx.constraintlayout.widget.ConstraintLayout>

It is also very simple to use. It's just to get something that occupies a place. But it seems that there should not be many usage scenarios