anchor.diff:  
   enum AppTab { profile, runs, futureEvents, pastEvents, offlineChart }
   
  -Map<AppTab, GlobalKey<NavigatorState>> navigatorKeys = {
  -  AppTab.profile: GlobalKey<NavigatorState>(),
  -  AppTab.runs: GlobalKey<NavigatorState>(),
  -  AppTab.futureEvents: GlobalKey<NavigatorState>(),
  -  AppTab.pastEvents: GlobalKey<NavigatorState>(),
  -  AppTab.offlineChart: GlobalKey<NavigatorState>()
  -};
  -
   class Home extends StatefulWidget {
     Home({Key key}) : super(key: key);
   
  
positive.code: class _HomeState extends State<Home> {
    static const TextStyle optionStyle =
        TextStyle(fontSize: 30, fontWeight: FontWeight.bold);
    static final List<Widget> _widgetOptions = <Widget>[
      TabNavigator(
        navigatorKey: navigatorKeys[AppTab.profile],
        routes: {
          '/': (context) => ProfileDashboard(),
        },
      ),
      TabNavigator(
        navigatorKey: navigatorKeys[AppTab.runs],
        routes: {
          '/': (context) => UserRunsPage(),
          '/run-details': (context) => RunDetailsPage(),
        },
      ),
      TabNavigator(
        navigatorKey: navigatorKeys[AppTab.pastEvents],
        routes: {
          '/': (context) => PastEventsPage(),
          '/event-results': (context) => EventResultsPage(),
        },
      ),
      TabNavigator(
        navigatorKey: navigatorKeys[AppTab.futureEvents],
        routes: {
          '/': (context) => FutureEventsPage(),
        },
      ),
      TabNavigator(
        navigatorKey: navigatorKeys[AppTab.offlineChart],
        routes: {
          '/': (context) => OfflineChartPage(),
        }
      )
    ];
  
    int _selectedIndex = 0;
    TabNavigationHelper _tabHelper;
  
    set selectedIndex(value) {
      if (value != _selectedIndex) {
  
negative.code:   void initState() {
      super.initState();
      this._tabHelper = TabNavigationHelper(this);
      this._widgetOptions = <Widget>[
        TabNavigator(
          navigatorKey: this._tabHelper.navigatorKeys[AppTab.profile],
          routes: {
            '/': (context) => ProfileDashboard(),
          },
        ),
        TabNavigator(
          navigatorKey: this._tabHelper.navigatorKeys[AppTab.runs],
          routes: {
            '/': (context) => UserRunsPage(),
            '/run-details': (context) => RunDetailsPage(),
          },
        ),
        TabNavigator(
          navigatorKey: this._tabHelper.navigatorKeys[AppTab.pastEvents],
          routes: {
            '/': (context) => PastEventsPage(),
            '/event-results': (context) => EventResultsPage(),
          },
        ),
        TabNavigator(
          navigatorKey: this._tabHelper.navigatorKeys[AppTab.futureEvents],
          routes: {
            '/': (context) => FutureEventsPage(),
          },
        ),
        TabNavigator(
            navigatorKey: this._tabHelper.navigatorKeys[AppTab.offlineChart],
            routes: {
              '/': (context) => OfflineChartPage(),
            })
      ];
    }
  
    void _onItemTapped(int index) {
  