title: barrierDismissible in showGeneralDialog is not working with Scaffold
body: <p>I am still new with Flutter. I try to make my dialog to be able to dismiss when click outside of the dialog. However if i use Scaffold, the <em>barrierDismissible:true</em> is not working. I tried to use Wrap but an error : <em>No Material widget found</em> will be displayed. Is there any idea on how to dismiss the dialog?</p>
  <p>This is my code:</p>
  <pre><code>showGeneralDialog(
       barrierDismissible: true,
         pageBuilder: (context, anim1, anim2) {
           context1 = context;
            return StatefulBuilder(
               builder: (context, setState) {
                  return Scaffold(
                      backgroundColor: Colors.black .withOpacity(0.0),
                          body:  Align(
                            alignment: Alignment.bottomCenter,
                            child: Container(
                                 child: InkWell()
                                     )
                                    )
                                  }
                                }
                              )
  </code></pre>