Flutter pageview, add new elements at runtime - flutter

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 .