title: Flutter showDialog not working on a simple test
body: <p>I am trying flutter and have problems in making a simple showdialog work. I tried a simple test with one button:</p>
  
  <pre><code>import 'package:flutter/material.dart';
  
  void main() =&gt; runApp(MyApp());
  
  class MyApp extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return MaterialApp(
        title: 'Welcome to Flutter Test',
        home: Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.teal,
            title: Text('Flutter'),
          ),
          body: Center(
            child: ListView(
              padding: EdgeInsets.all(8),
              children: &lt;Widget&gt;[
                Container(
                  child: RaisedButton(
                    child: Text('My Button'),
                    onPressed: () =&gt; {
                      showDialog(
                        context: context,
                        barrierDismissible: false,
                        builder: (context) {
                          return AlertDialog(
                            title: Text('Test'),
                            content: Text('Dialog content'),
                          );
                        },
                      ),
                    },
                    color: Colors.cyan,
                    textColor: Colors.white,
                  ),
                ),
              ],
            ),
          ),
        ),
      );
    }
  }
  </code></pre>
  
  <p>I expect the alert to pop on button tap. What am I missing? I also tried it with the showdialog in a separate custom function call, same result.</p>