title: Blueprint view nor the constraints are now visible in Android Studio design view
body: <p>I had to edit the Constraint Layout XML file by hand (*), so I also removed all the <code>tools:</code> fields from the XML. To my understanding these attributes are only used by Android Studio and the Constraint Layout tool. But I removed them because I wanted to reset the state of the layout and changing the <code>android:</code> properties for the Constraint Layout surely would only mix things up even more, right?</p>
  
  <p>So I am now in a situation where the blueprint view stays empty and the hierarchy view says <code>"Nothing to show"</code>. I see no view properties and no constraints. I can only see the flat UI design view of the layout, but I can't select any elements from it either.</p>
  
  <p>Any ideas how to fix this? </p>
  
  <p>I am running Android Studio 2.2.3 and Constraint Layout beta 4. </p>
  
  <p>*) Why did I edit the layout by hand you ask? Well, I selected "Convert to Constraint Layout" in which case Android Studio just flattened my layout and hard coded the positions of all elements. Which wasn't exactly what I wanted since then I couldn't change the positions anymore. Removing the hard coded positions (and the tools: arguments) let me re-structure my layout. </p>