ConstraintLayout: how to have a view be half the screen width and centered?

Question

TL;DR
The view width must be exactly half of the screen, and be centered. Using ConstraintLayout.

Note that the view does not have

Answer 1

As of** ConstraintLayout1.1.0-beta1**, you can use percent to define widths & heights.

android:layout_width="0dp"
app:layout_constraintWidth_default="percent"
app:layout_constraintWidth_percent=".4"

This will define the width to be 40% of the width of the screen. A combination of this and guidelines in percent allow you to create any percent based layout you want.