set of views directly in XML <android.support.constraint.Group android:id="@+id/group" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="visible" app:constraint_referenced_ids="button4,button9"/>
o-motionlayout-part-i-29208674b10d) • ConstraintLayout github example repo (https://github.com/googlesamples/android-Constraint LayoutExamples) • Google IO 2018 talk on ConstraintLayout and MotionLayout (https://www.youtube.com/watch?v=ytZteMo4ETk)