How to Navigate to parent of widget in flutter

I want to navigate to the second bottom item on a page in flutter, from other pages.

The parent here is BottomNavigationBar that I want to configure to change the page (I define a key for it in Provider to access it from other pages).

 List<Widget> pages = new List<Widget>();
  BottomNavigationBar bottomNavigationBar;

  updateList(){
    pages.addAll({
      Dashboard(),
      AllServices(),
      Account(),
      Charge(),
    });
  }

  int _selectedIndex = 0;

  Widget _bottomNavigationBar(int selectedIndex,key)  {
    return BottomNavigationBar(
      key: key,
      onTap: (int index) => setState(() => _selectedIndex = index),
      currentIndex: selectedIndex,
      type: BottomNavigationBarType.fixed,
      items: <BottomNavigationBarItem>[
        BottomNavigationBarItem(
          icon: new Icon(Icons.home),
          title:  new Text("A page"),
        ),
        BottomNavigationBarItem(
          icon: new Icon(Icons.location_on),
          title: new Text("B page")
        ),
        BottomNavigationBarItem(
          icon: new Icon(Icons.store),
          title: new Text("C page")
        ),
        BottomNavigationBarItem(
          icon: new Icon(Icons.person),
          title:new Text("D page")
        ),
      ],
    );

  }

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    updateList();
  }

  @override
  Widget build(BuildContext context) {
    final globalKeyForBottomNavigate =  Provider.of<Controller>(context, listen: false).bottomNavigate;

    return Scaffold(
      bottomNavigationBar: _bottomNavigationBar(_selectedIndex,globalKeyForBottomNavigate),
      body: pages[_selectedIndex],
    );
  }

And children are Page A, B, C, D. now from page A I Navigate to Page F. Then if an action is triggered, I want to navigate to page B, but my solution is to change the index of BottomNavigationBar in page F and then navigate to page A. It works, but does not directly navigate to the content of page B and the BottomNavigationBar. In my solution, I say ok first change index of BottomNavigationBar, then go to last page (that here is Page A), but as you see, I do not know how to directly navigate to page B. This is the code for page F.

onTap: (){
        var bottomKey=Provider.of<Controller>(context, listen: false).bottomNavigate;

        final BottomNavigationBar navigationBar = bottomKey.currentWidget;
        navigationBar.onTap(1);

        Navigator.pop(context);

      },