title: How to prevent AlertDialog from not closing by clicking outside?
body: <p>I built an AlertDialog to display Loading while i'm authenticating the user and when it finishes i pop it. </p>
  
  <pre><code>Widget loadingDialog = new AlertDialog(
  content: new Row(
    children: &lt;Widget&gt;[
      new CircularProgressIndicator(),
      Padding(
        padding: const EdgeInsets.only(left: 8.0),
        child: new Text("Loading..."),
      ),
    ],
  ),);
  </code></pre>
  
  <p>But, if the user taps outside the Dialog it closes. So when the auth finishes, it will still pop something (i guess the scaffol), breaking the app.
  How can i make Dialog not closable? </p>