title: Navigation Preview unavailable in Android Studio 3.2 Preview
body: <p>I am interested to try the Navigation graph showed in the Android Studio. But I got the preview unavailable after I import the <a href="https://developer.android.com/jetpack/docs/ComponentsBasicSample.zip" rel="noreferrer">google sample</a></p>
  
  <p>I used the Android Studio 3.2 Preview Canary 16</p>
  
  <p><a href="https://i.stack.imgur.com/stHfy.png" rel="noreferrer"><img src="https://i.stack.imgur.com/stHfy.png" alt="enter image description here"></a></p>
  
  <pre><code>&lt;navigation xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      app:startDestination="@+id/launcher_home"&gt;
  
      &lt;fragment
          android:id="@+id/launcher_home"
          android:name="com.android.samples.arch.componentsbasicsample.StartFragment"
          android:label="Home"&gt;
  
          &lt;action
              android:id="@+id/end_action"
              app:destination="@id/end_dest" /&gt;
  
      &lt;/fragment&gt;
  
      &lt;fragment
          android:id="@+id/end_dest"
          android:name="com.android.samples.arch.componentsbasicsample.EndFragment"
          android:label="End"
          &gt;
  
      &lt;/fragment&gt;
  &lt;/navigation&gt;
  </code></pre>
  
  <p><strong>Update on 10/6/2018:</strong></p>
  
  <p>Even I rebuild the project it doesn't work. But if added new screen, it showed the new one in preview mode</p>
  
  <p><a href="https://i.stack.imgur.com/375I7.png" rel="noreferrer"><img src="https://i.stack.imgur.com/375I7.png" alt="enter image description here"></a></p>