Flutter pageview, add new elements at runtime

Question

In my project I have a Pageview which contains widgets from a list. In runtime I add more elements to this list to show it in the Pageview. If I don't specify itemCounter than I can run out of index but I can see the new pages, however, if use itemCounter, the new page will not appear. For the itemCounter I use the length of my list. How can I add new elements runtime to a pageview?

In this case I can add new elements, but I can run out of index:

child: PageView.builder(
          controller: pageController,
          //itemCount: _dummy.length,
          itemBuilder: (context, position) {
            return _dummy[position];
          },
        ),
      ),

This is case the new pages doesn't even show up. It's like the itemCounter doesn't change.

child: PageView.builder(
          controller: pageController,
          itemCount: _dummy.length,
          itemBuilder: (context, position) {
            return _dummy[position];
          },
        ),
      ),

Answer 1

in this widget, when you clickfab it will create another page in PageView.

import 'package:flutter/material.dart';

class PageViewOnRuntime extends StatefulWidget {
  PageViewOnRuntime({Key? key}) : super(key: key);

  @override
  _PageViewOnRuntimeState createState() => _PageViewOnRuntimeState();
}

class _PageViewOnRuntimeState extends State<PageViewOnRuntime> {
  final PageController pageController = PageController();

  int numberOfPage = 2;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: PageView.builder(
        controller: pageController,
        itemCount: numberOfPage,
        itemBuilder: (context, index) {
          return Container(
            color: index % 2 == 0 ? Colors.cyanAccent : Colors.blueGrey,
            alignment: Alignment.center,
            child: Text(index.toString()),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          setState(() {
            numberOfPage++;
          });
        },
        child: Icon(Icons.add),
      ),
    );
  }
}

let me know , if you need something else .