Align ConstraintLayout item to be at the end of two items

Question

I have a ConstraintLayout with two views A and B that are stacked vertically. I have a third view C which needs to be to the end of both A and B horizontally. At any given point

Answer 1

This can be easily achieved using the new Barriers feature.

How to use Barriers ?

Barriers are like building a HUUUUGE WALL that "protects" the views mentioned in constraint_referenced_ids. So, you have to mention which direction it's "supposed to keep out" which in our case is the right (view_c). Just use the barrierDirection attribute.
Finally, don't forget to make sure that view_c is in the keep out zone (layout_constraintLeft_toRightOf="@+id/barrier1").

As this feature is available only in the 1.1.0 beta1 release of ConstraintLayout, don't forget to add this line to your build.gradle file.

compile 'com.android.support.constraint:constraint-layout:1.1.0-beta1'

Hope this helps!