title: Display an ActionBarCompat Activity as a dialog
body: <p>I have an Activity inherited from AppCompactActivity. in manifest for activity set theme:</p>
  
  <pre><code>&lt;activity
              android:name=".activity.CameraSettingsActivity2"
              android:theme="@style/Theme.AppCompat.Light.Dialog" /&gt;
  </code></pre>
  
  <p>but the activity still displays in a fullscreen instead of dialog window.
  I have been trying different themes such as ..</p>
  
  <pre><code>Theme.AppCompat.Dialog
  Theme.AppCompat.Dialog.Alert
  Theme.AppCompat.Dialog.MinWidth
  </code></pre>
  
  <p>none of them seems work.the activity still like this</p>
  
  <p><img src="https://i.stack.imgur.com/LvN7c.png" alt="enter image description here"></p>