All child views' widths have to match the widest child view's width

constraintlayout_widest_child.xml

<android.support.constraint.ConstraintLayout 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">

    <TextView
        android:id="@+id/button1_txt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:elevation="8dp"
        android:padding="16dp"
        android:text="text"
        android:textColor="@android:color/black"
        app:layout_constraintBottom_toTopOf="@+id/button2_txt"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.2"
        app:layout_constraintVertical_chainStyle="packed" />

    <TextView
        android:id="@+id/button2_txt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:elevation="8dp"
        android:padding="16dp"
        android:text="Long text"
        android:textColor="@android:color/black"
        app:layout_constraintBottom_toTopOf="@+id/button3_txt"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button1_txt" />

    <TextView
        android:id="@+id/button3_txt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:elevation="8dp"
        android:padding="16dp"
        android:text="An extremely long text!"
        android:textColor="@android:color/black"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2_txt" />

    <View
        android:id="@+id/button1"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@drawable/bg"
        app:layout_constraintBottom_toBottomOf="@+id/button1_txt"
        app:layout_constraintLeft_toLeftOf="@+id/left_barrier"
        app:layout_constraintRight_toRightOf="@+id/right_barrier"
        app:layout_constraintTop_toTopOf="@+id/button1_txt" />

    <View
        android:id="@+id/button2"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@drawable/bg"
        app:layout_constraintBottom_toBottomOf="@+id/button2_txt"
        app:layout_constraintLeft_toLeftOf="@+id/left_barrier"
        app:layout_constraintRight_toRightOf="@+id/right_barrier"
        app:layout_constraintTop_toTopOf="@+id/button2_txt" />

    <View
        android:id="@+id/button3"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="@drawable/bg"
        app:layout_constraintBottom_toBottomOf="@+id/button3_txt"
        app:layout_constraintLeft_toLeftOf="@+id/left_barrier"
        app:layout_constraintRight_toRightOf="@+id/right_barrier"
        app:layout_constraintTop_toTopOf="@+id/button3_txt" />

    <android.support.constraint.Barrier
        android:id="@+id/right_barrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="end"
        app:constraint_referenced_ids="button1_txt, button2_txt, button3_txt" />

    <android.support.constraint.Barrier
        android:id="@+id/left_barrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="start"
        app:constraint_referenced_ids="button1_txt, button2_txt, button3_txt" />

</android.support.constraint.ConstraintLayout>