animation.kt

fun animate() {
        view2.visibility = View.VISIBLE
        val params = ConstraintLayout.LayoutParams(-1, -1)
        view2.layoutParams = params
        val set = ConstraintSet()
        set.connect(view2.id, ConstraintSet.TOP, root.id, ConstraintSet.TOP)
        set.connect(view2.id, ConstraintSet.BOTTOM, view1.id, ConstraintSet.BOTTOM)
        set.connect(view2.id, ConstraintSet.START, view1.id, ConstraintSet.END)
        set.connect(view2.id, ConstraintSet.END, view3.id, ConstraintSet.START)
        val transition = AutoTransition()
        transition.duration = 1000
        TransitionManager.beginDelayedTransition(root, transition)
        set.applyTo(root)
    }

view.xml

<androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/root"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <View
            android:id="@+id/view1"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:background="@color/colorPrimary"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <View
            android:id="@+id/view2"
            android:layout_width="1px"
            android:layout_height="40dp"
            android:background="@color/colorPrimaryDark"
            android:visibility="invisible"
            app:layout_constraintEnd_toStartOf="@id/view3"
            app:layout_constraintStart_toEndOf="@id/view1"
            app:layout_constraintTop_toTopOf="parent" />

        <View
            android:id="@+id/view3"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:background="@color/colorPrimary"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </androidx.constraintlayout.widget.ConstraintLayout>