Why you should prefer getter for state objects in Flutter.

sample.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  final String title;

  const MyHomePage({
    Key? key,
    required this.title,
  }) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: const MyList(),
    );
  }
}

class MyList extends StatefulWidget {
  const MyList({
    Key? key,
  }) : super(key: key);

  @override
  State<MyList> createState() => _MyListState();
}

class _MyListState extends State<MyList> {
  int multiplier = 0;

  @override
  Widget build(BuildContext context) {
    return GestureDetector(
      onTap: () {
        setState(() {
          multiplier++;
        });
      },
      child: ListView.builder(itemBuilder: (context, index) {
        return ListItem(
          index: index * multiplier,
        );
      }),
    );
  }
}

class ListItem extends StatefulWidget {
  final int index;

  const ListItem({
    Key? key,
    required this.index,
  }) : super(key: key);

  @override
  State<ListItem> createState() => _ListItemState();
}

class _ListItemState extends State<ListItem> {
  late final int index = widget.index;

  @override
  Widget build(BuildContext context) {
    return Text(index.toString());
  }
}