MotionLayout OnSwipe transition gets triggered by wrong anchor

Question

So we're trying to mimic the behaviour of a peek-able BottomSheetLayout (a bottom View peeking out from the bottom of the screen, which comes into full-screen view when scrolling it upwards, sort of like this: https://www.youtube.com/watch?v=yrZVLL-z6P4) using MotionLayout, version 2.0.0-alpha4.

The problem is that the OnSwipe transition on the peek-able view doesn't apply to the View itself, it apparently applies to the entire view underneath, in this case a RecyclerView. So when we scroll the RecyclerView, the transition is being run.

root_view.xml

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.constraintlayout.motion.widget.MotionLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layoutDescription="@xml/motion_scene">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/recyclerview"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:clipToPadding="false"
            android:paddingBottom="@dimen/margin_48"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/btn"
            android:layout_width="match_parent"
            android:layout_height="@dimen/size_48"
            android:elevation="@dimen/elevation_12"
            android:gravity="center"
            app:layout_constraintBottom_toBottomOf="parent" />

        <androidx.appcompat.widget.AppCompatImageView
            android:id="@+id/arrow"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:elevation="@dimen/elevation_12"
            android:rotation="90"
            app:layout_constraintBottom_toBottomOf="@id/btn"
            app:layout_constraintEnd_toEndOf="@id/btn"
            app:layout_constraintTop_toTopOf="@id/btn" />

        <FrameLayout
            android:id="@+id/fragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:elevation="@dimen/elevation_8"
            app:layout_constraintTop_toBottomOf="parent" />
    </androidx.constraintlayout.motion.widget.MotionLayout>
</FrameLayout>

motion_scene.xml

<Transition
    android:id="@+id/swipe"
    app:constraintSetEnd="@id/end"
    app:constraintSetStart="@id/start"
    app:duration="250">

    <OnSwipe
        app:dragDirection="dragUp"
        app:touchAnchorId="@id/btn" />
</Transition>

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

    <Constraint
        android:id="@id/fragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toBottomOf="parent" />

    <Constraint
        android:id="@id/btn"
        android:layout_width="match_parent"
        android:layout_height="@dimen/size_48"
        app:layout_constraintBottom_toBottomOf="parent" />
</ConstraintSet>

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

    <Constraint
        android:id="@id/fragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintTop_toBottomOf="@id/btn" />

    <Constraint
        android:id="@id/btn"
        android:layout_width="match_parent"
        android:layout_height="@dimen/size_48"
        app:layout_constraintTop_toTopOf="parent" />
</ConstraintSet>

Answer 1

using both app:touchAnchorId and app:touchRegionId together helped me.

<OnSwipe
    app:dragDirection="dragUp"
    app:touchAnchorId="@id/btn" 
    app:touchRegionId="@id/btn"/>