title: How to use new features in constraint layout 1.1?
body: <p>Does anyone know how to use new features in constraint layout 1.1, namely barriers and percent-based dimensions? There is absolutely no documentation available online, and the recent Google I/O talk on designer tools covered in detail only placeholders. BTW, I found out how to use groups, which are also a new feature. You need to simply add</p>
  
  <pre><code>&lt;android.support.constraint.Group
      app:constraint_referenced_ids="button1, button2"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/&gt;
  </code></pre>
  
  <p>to your constraint layout, where app:constraint_referenced_ids is a string, where you should enumerate comma separated ids of views, that you want to be associated with this group. Now, toggling the visibility of a group changes the visibility of all the views referenced by it, which I think is the main purpose of this feature right now.</p>