anchor.diff:            title: 'P2P Call Sample',
             subtitle: 'P2P Call Sample.',
             push: (BuildContext context) {
  -            showDialog<Null>(
  -                context: context,
  -                builder: (BuildContext context) {
  -                  return SimpleDialog(
  -                    title: const Text('Please input server address.'),
  -                    children: <Widget>[
  -                      TextField(
  -                        onChanged: (String text) {
  -                          setState(() {
  -                            _serverAddress = text;
  -                          });
  -                        },
  -                        decoration: InputDecoration(
  -                          hintText: _serverAddress,
  -                        ),
  -                        textAlign: TextAlign.center,
  -                      ),
  -                      SimpleDialogOption(
  -                        onPressed: () {},
  -                        child: RaisedButton(
  -                          onPressed: () {
  -                            prefs.setString('server', _serverAddress);
  -                            Navigator.push(
  -                                context,
  -                                MaterialPageRoute(
  -                                    builder: (BuildContext context) =>
  -                                        CallSample(ip: _serverAddress)));
  -                          },
  -                          child: const Text('Connect Server'),
  -                        ),
  -                      ),
  -                    ],
  -                  );
  -                });
  +            _showAddressDialog(context);
             }),
       ];
     }
  
positive.code:     });
    }
  
    _initItems() {
      items = <RouteItem>[
        RouteItem(
  
negative.code: class MyApp extends StatefulWidget {
    @override
    _MyAppState createState() => new _MyAppState();
  }
  
  enum DialogDemoAction {
    cancel,
    connect,
  }
  
  class _MyAppState extends State<MyApp> {
  