How can I scale textView inside parent view with motion layout?

Question

I'm trying to scale a textView inside a container view. Activity uses a motion layout. I can scale the textView if I don't place it inside the container. Here is my activity layout and the motion layout description file. How can I make scaleX and scaleY work?

Activity Layout

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.motion.MotionLayout xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/motionLayout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layoutDescription="@xml/motion_scene_text_size">

    <View
        android:id="@+id/button"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:background="@color/colorAccent"
        android:text="Button" />

    <android.support.constraint.ConstraintLayout
        android:id="@+id/container"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginTop="100dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="20sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

    </android.support.constraint.ConstraintLayout>

</android.support.constraint.motion.MotionLayout>

Motion scene

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

    <Transition
        motion:constraintSetStart="@+id/start"
        motion:constraintSetEnd="@+id/end"
        motion:duration="1000">
        <OnSwipe
            motion:touchAnchorId="@+id/button"
            motion:touchAnchorSide="right"
            motion:dragDirection="dragRight" />
    </Transition>

    <ConstraintSet android:id="@+id/start">
        <Constraint
            android:id="@id/button"
            android:layout_width="64dp"
            android:layout_height="64dp"
            android:layout_marginStart="8dp"
            motion:layout_constraintBottom_toBottomOf="parent"
            motion:layout_constraintStart_toStartOf="parent"
            motion:layout_constraintTop_toTopOf="parent" />

        <Constraint
            android:id="@id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="20sp"
            android:scaleX="1.0"
            android:scaleY="1.0"
            motion:layout_constraintBottom_toBottomOf="parent"
            motion:layout_constraintEnd_toEndOf="parent"
            motion:layout_constraintStart_toStartOf="parent"
            motion:layout_constraintTop_toTopOf="parent" />

    </ConstraintSet>

    <ConstraintSet android:id="@+id/end">
        <Constraint
            android:id="@id/button"
            android:layout_width="64dp"
            android:layout_height="64dp"
            android:layout_marginEnd="8dp"
            motion:layout_constraintBottom_toBottomOf="parent"
            motion:layout_constraintEnd_toEndOf="parent"
            motion:layout_constraintTop_toTopOf="parent" />

        <Constraint
            android:id="@id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView"
            android:textSize="20sp"
            android:scaleX="2.0"
            android:scaleY="2.0"
            motion:layout_constraintBottom_toBottomOf="parent"
            motion:layout_constraintEnd_toEndOf="parent"
            motion:layout_constraintStart_toStartOf="parent"
            motion:layout_constraintTop_toTopOf="parent" />

    </ConstraintSet>

</MotionScene>

Answer 1

It's worth noting that you can only animate direct children of a MotionLayout.

If you have to use this container, you could use matchParent for the height and width of your TextView and then use AutoSizeText.

<MotionLayout
   ...>

   <ConstraintLayout
    android:id="@+id/container"
    ...>

      <TextView
       android:layout_width="matchParent"
       android:layout_height="matchParent"
       app:autoSizeTextType="uniform"
       app:autoSizeMinTextSize="20sp"
       app:autoSizeMaxTextSize="40sp"
       .../>

   </ConstraintLayout>

</MotionLayout>

In your MotionScene, change the size of the ConstraintLayout:

<ConstraintSet android:id="@+id/endConstraintSet">

   <Constraint
    android:id="@id/container"
    android:layout_width="200dp"
    android:layout_height="200dp"
    ... />

</ConstraintSet />