Flow usage

flow.xml

        <android.support.constraint.helper.Flow
            android:layout_width="0dp"
            android:layout_height="0dp"
            app:constraint_referenced_ids="ac, plus_minus_switch, percentage, divide,
                                           seven, eight, nine, multiply,
                                           four, five, six, plus,
                                           one, two, three, minus,
                                           zero, comma"
            app:flow_firstHorizontalStyle="spread"
            app:flow_horizontalStyle="spread"
            app:flow_maxElementsWrap="4"
            app:flow_verticalStyle="spread"
            app:flow_wrapMode="aligned"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="@id/operation_result_dividing_guideline" />