ConstraintLayout XML example

gistfile1.txt

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <Button
            android:id="@+id/button"
            android:layout_width="200dp"
            android:layout_height="56dp"
            android:text="CLick"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <TextView
            android:id="@+id/text"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            app:layout_constraintEnd_toEndOf="@+id/button"
            app:layout_constraintStart_toStartOf="@+id/button"
            app:layout_constraintTop_toBottomOf="@+id/button" />
    </androidx.constraintlayout.widget.ConstraintLayout>