anchor.diff:      Profile(),
     ];
   
  -  int selectedIndex = 0;
  -
     final List<String> tabNames = ['home', 'maps', 'notifications', 'profile'];
   
     @override
  
positive.code: 
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: PreferredSize(
          preferredSize: Size.fromHeight(42),
  
negative.code:   _BottomTabBarState(this.observer);
  
    final FirebaseAnalyticsObserver observer;
    int selectedIndex = 0;
  
    @override
    void didChangeDependencies() {
  