CODE EXAMPLE FOR DART

showdialog with builder flutter

showDialog(
        context: context,
        builder: (BuildContext context) => new AlertDialog(
          title: new Text('Warning'),
          content: new Text('Hi this is Flutter Alert Dialog'),
          actions: <Widget>[
            new IconButton(
                icon: new Icon(Icons.close),
                onPressed: () {
                  Navigator.pop(context);
                })
          ],
        ));