Button to simulate action on navigation bar

Hello,

I can not create a button that allows me to change the page as if I clicked on a button on my navigation bar to load a main page.

Example if in my menu I have page 1, page 2, page 3.
On my page 1 I have a button which allows me to push a page 1.1 above. In this page 1.1, I have a button that allows me to load page 2 but it is added to the stack when I want it to load page 2 as if I clicked on the button on my navigation bar.
The page 2 is add to the Stack (1->1.1->2). But If I click on the page 2 in my navigation bar, the page 2 is reloaded without Stack. I want to do this directly when I click on my button I want to simulate as I click on my navigation bar button

How to do that ?

My navigationBar :

...
class _MyBottomNavigationBarState extends State<MyBottomNavigationBar>
{
  @override
  Widget build(BuildContext context) {
    return CupertinoTabScaffold(
      tabBar: CupertinoTabBar(
        iconSize: 30,
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            title: Text(
              'Page 1',
            ),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.search),
            title: Text(
              'Page 2',
            ),
          ),
        ],
      ),
      tabBuilder: (context, index) {
        switch (index) {
          case 0:
            return CupertinoTabView(builder: (context) {
              return CupertinoPageScaffold(
                child: Page1(),
              );
            });
          case 1:
            return CupertinoTabView(builder: (context) {
              return CupertinoPageScaffold(
                child: Page2(),
              );
            });
          default: return CupertinoTabView(builder: (context) {
            return CupertinoPageScaffold(
              child: Page1(),
            );
          });
        }
      },
    );
  }

In my page1.1 I have this Widget button for load the page 2:

Widget _getSubmitButton(){
    return RaisedButton(
      child: Text(
        'Page 2',
        style: TextStyle(color: Colors.blue, fontSize: 16),
      ),
      onPressed: () {
        Navigator.pushReplacement(
          context,
          MaterialPageRoute(
            builder : (BuildContext context) => Page2(data : data),
          ),
        );
      },
    );
  }

How can I prevent the page from adding to the stack but loading as if I clicked on my navigation bar? By selecting the correct icon on my navigation bar.
I want to do this because my page 2 is a form and I want to send data in this form if I click on the button of my page 1.1.