anchor.diff:  
     TabController _tabController;
     TextEditingController _usernameEditingController;
  -  CodeWarsUser _user;
  +  CodeWarsUser _user = new CodeWarsUser();
     _Page _selectedPage;
   
     @override
  
positive.code: 
    Widget buildTabView(_Page page) =>
        new Container(
            key: new ValueKey<String>(page.displayWhenEmpty),
            color: _background,
            padding: const EdgeInsets.fromLTRB(8.0, 8.0, 8.0, 32.0),
            child: page.childWight
        );
  
    _changeUserName() {
      var dialog = new SimpleDialog(
  
negative.code:   Widget get childWight =>
        child ?? new Card(
            color: CodeWarsColors.black.shade300,
            child: new Center(child: new Text(displayWhenEmpty,
                style: new TextStyle(color: labelColor, fontSize: 32.0),
                textAlign: TextAlign.center)));
  }
  
  class TabsFabDemo extends StatefulWidget {
  