How to pass data to the class of another screen in Flutter/Dart?

I need to pass the value of two variables from one screen to another screen class. I can’t do it.

Here is the whole code:

import 'package:flutter/material.dart';
import 'package:csv/csv.dart';
import 'package:flutter/services.dart' show rootBundle;
import 'dart:io';


//My classes
import './my classes.dart';

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title="Example";

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
        home: Container(
            child: Scaffold(
        appBar: AppBar(title: const Text(_title)),
        // body: const MyStatelessWidget(),
              body: const MainWidget(),
      ),
    )
    );
  }
}

// class MyStatelessWidget extends StatelessWidget {
//   const MyStatelessWidget({Key? key}) : super(key: key);
class MainWidget extends StatefulWidget {
  const MainWidget({Key? key}) : super(key: key);

  @override
  State<MainWidget> createState() => _MainWidgetState();
}


class _MainWidgetState extends State<MainWidget> {
  CheckUserConnection _checkUserConnection = CheckUserConnection();
  InternetDialogHandler _internetDialogHandler = InternetDialogHandler();
  bool? _internetAvailable;

  @override
  void initState(){
    checkNet();
    super.initState();
  }


  void checkNet() async{
    _internetAvailable = await
    _checkUserConnection.checkInternetAvailability();
    setState((){});
  }



  @override
  Widget build(BuildContext context) {
    return Center(
      child: Column(
        mainAxisSize: MainAxisSize.max,
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: <Widget>[
          Column(
            children: [
              GradientButton(label: 'New Game', onTap: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const NewGameRoute(
                      listCount: 0, assetPath: "images/01.jpg" ///What I want to pass


                  )),
                );
              }),
              // GradientButton(label: 'Continue Game', onTap: () {
              //   return _internetAvailable == true ?
              //   {Navigator.push(
              //         context,
              //         MaterialPageRoute(builder: (context) => const NewGameRoute()),
              //       )}
              //   :
              //   _internetDialogHandler.showInternetDialog(context);
              // }),
            ],
          ),
          Column(
            children: [
              GradientButton(label: 'Back Button', onTap: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const BackRoute()),
                );



                // print('Button 1');



              }),
              GradientButton(label: 'Button 2', onTap: () {print('Button 2');}),
              GradientButton(label: 'Internet', onTap: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const InternetRoute()),
                );
              }),
            ],
          )
        ],
      ),
    );
  }
}


//Class for a gradient button
class GradientButton extends StatelessWidget {
  const GradientButton({Key? key, required this.label, required this.onTap}) : super(key: key);
  final String label;
  final Function onTap;

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: const EdgeInsets.symmetric(vertical: 15),
      child: GestureDetector(
        onTap: () => onTap(),
        child: Container(
          padding: const EdgeInsets.symmetric(horizontal: 20, vertical: 8),
          decoration: const BoxDecoration(
            borderRadius: BorderRadius.all(Radius.circular(4)),
            gradient: LinearGradient(
              colors: <Color>[
                Color(0xFF0D47A1),
                Color(0xFF1976D2),
                Color(0xFF42A5F5),
              ],
            ),
          ),
          child: Text(label, style: const TextStyle(fontSize: 20, color: Colors.white, fontWeight: FontWeight.normal, decoration: TextDecoration.none),),
        ),
      ),
    );
  }
}


// New Game route
var globalContext; // Declare global variable to store context from StatelessWidget

// class NewGameRoute extends StatelessWidget {
//   const NewGameRoute({key});  //original



  class NewGameRoute extends StatelessWidget {
    const NewGameRoute({
      Key? key,
      required int listCount,
      required this.assetPath,
    })  : _listCount = listCount,
          super(key: key);

    final int _listCount;

    final String assetPath;



  @override
  Widget build(BuildContext context) {
    globalContext = context; // globalContext receives context from StatelessWidget.
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'New Game',
      home: ListFromCSV(),
    );
  }
}

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

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

class _ListFromCSVState extends State<ListFromCSV> {
  List<List<dynamic>> _listData = [
    [""]
  ];
  // int _listCount = 0;
  bool _isFirstLoad = true;
  // String assetPath = "files/main.jpg";

  @override
  void initState() {
    _loadCSV();
  }

  // This function is only triggered at init, so we only load csv once
  void _loadCSV() async {
    String rawData = await rootBundle.loadString("files/Text.csv");
    _listData = const CsvToListConverter().convert(rawData);
    // assetPath = _listData[_listCount][1] == ""
    //     ? "files/main.jpg"
    //     : _listData[_listCount][1];
  }
///


  // This function is triggered when my button is pressed
  void _nextCSV() {
    setState(() {
      _listData = _listData;
      _listCount < _listData.length - 1
          ? _isFirstLoad
          ? _isFirstLoad = false
          : _listCount++
          : _listCount;
      // assetPath =
      // _listData[_listCount][1] == "" ? assetPath : _listData[_listCount][1];
      _listData[_listCount][1] == "" ? null : _showAlertDialog();
    });
  }

  // This function makes buttons visible/invisible
  bool isVisible = true; //will be visible for the first frame

  void _isVisible() {
    setState(() {
      isVisible = !isVisible;
    });
  }


//Alert Dialog about questions and answers
  Widget _answer1TextButton(){
    return TextButton(
      child: Text(_listData[_listCount][3]),
      onPressed:  () {
        setState(() {
        assetPath = _listData[_listCount][6];
        _listCount = _listData[_listCount][2]-1;
        // _listData[_listCount][0];
        // _nextCSV();
        print('Answer 1');
        print(_listCount);
        Navigator.of(globalContext).pop();  // Popping globalContext
          });
      },
    );
  }
  Widget _answer2TextButton(){
    return TextButton(
      child: Text(_listData[_listCount][5]),
      onPressed:  () {
        setState(() {
        assetPath = _listData[_listCount][7];
        _listCount = _listData[_listCount][4]-1;
        print('Answer 2');
        print(_listCount);
        Navigator.of(globalContext).pop();  // Popping globalContext
        });
        },
    );
  }

  void _showAlertDialog() {

// set up the AlertDialog
    AlertDialog alert = AlertDialog(
      // title: Text(),
      content: Text(_listData[_listCount][1]),
      actions: [
        _answer1TextButton(),
        _answer2TextButton(),
      ],
    );

// show the dialog
    showDialog(
      barrierDismissible: false,  //use to dismiss any tap on the background of the dialog
      context: context,
      // useRootNavigator: false, //this property needs to be added
      builder: (BuildContext context) {
        return WillPopScope(
          onWillPop: () async {
            return true;   // false to disable the back button
          },
          child: alert,
        );
      },
    );
  }



  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: const Text('New Game'),
        ),
        body: Container(
          height: MediaQuery.of(context).size.height,
          decoration: BoxDecoration(
              image: DecorationImage(
                  image: AssetImage(assetPath),
                  fit: BoxFit.cover)),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: <Widget>[
              Visibility(
                child: Column(
                  children: [
                    ClipRRect(
                      borderRadius: BorderRadius.circular(4),
                      child: Stack(
                        children: <Widget>[
                          Positioned.fill(
                            child: Container(
                              decoration: BoxDecoration(
                                  image: DecorationImage(
                                      image: AssetImage('files/sheet.jpg'),
                                      fit: BoxFit.cover)),
                            ),
                          ),
                          Text(_listData[_listCount][0]),
                        ],
                      ),
                    ),
                    Row(
                      mainAxisAlignment: MainAxisAlignment.spaceAround,
                      children: [
                        ImageButton(label: 'OK', onButtonTap: _nextCSV),
                        ImageButton(label: 'Hide', onButtonTap: _isVisible),
                        ImageButton(label: 'Test1', onButtonTap: _showAlertDialog),
                      ],
                    ),
                  ],
                ),
                visible: isVisible,
              ),
              // your other widgets
              Visibility(
                child: ImageButton(label: 'Show', onButtonTap: _isVisible),
                visible: !isVisible,
              )

            ],
          ),
        ),
      );
  }
}


//Class for a cool button
class ImageButton extends StatelessWidget {
  const ImageButton({Key? key, required this.label, required this.onButtonTap})
      : super(key: key);
  final String label;
  final Function onButtonTap;

  @override
  Widget build(BuildContext context) {
    return InkWell(
      onTap: () => onButtonTap(),
      child: Container(
        // customize you button shape and size and design
        margin: const EdgeInsets.all(8),
        padding: const EdgeInsets.symmetric(vertical: 8, horizontal: 32),
        decoration: const BoxDecoration(
            borderRadius: BorderRadius.all(Radius.circular(2)),
            image: DecorationImage(
                image: AssetImage("files/sheet.jpg"), // you can also pass the image dynamically with variable created for the widget.
                fit: BoxFit.cover)),
        child: Center(
          child: Text(
            label,
            style: const TextStyle(
                color: Colors
                    .black, // you can get dominant colour on image and change the text color accordingly or apply shadows to the text
                fontWeight: FontWeight.w500,
                fontSize: 16),
          ),
        ),
      ),
    );
  }
}

This is how I pass data from the main screen:

GradientButton(label: 'New Game', onTap: () {
                Navigator.push(
                  context,
                  MaterialPageRoute(builder: (context) => const NewGameRoute(
                      listCount: 0, assetPath: "images/01.jpg" ///What I want to pass


                  )),
                );
              }),

This is how I get the data in another screen:

class NewGameRoute extends StatelessWidget {
    const NewGameRoute({
      Key? key,
      required int listCount,
      required this.assetPath,
    })  : _listCount = listCount,
          super(key: key);

    final int _listCount;

    final String assetPath;
...

But when I try to run my file I get the following errors:

Performing hot reload...
Syncing files to device sdk gphone64 x86 64...
lib/main.dart:223:7: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
      _listCount < _listData.length - 1
      ^^^^^^^^^^
lib/main.dart:226:13: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
          : _listCount++
            ^^^^^^^^^^
lib/main.dart:226:13: Error: The setter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing setter, or defining a setter or field named '_listCount'.
          : _listCount++
            ^^^^^^^^^^
lib/main.dart:227:13: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
          : _listCount;
            ^^^^^^^^^^
lib/main.dart:230:17: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
      _listData[_listCount][1] == "" ? null : _showAlertDialog();
                ^^^^^^^^^^
lib/main.dart:247:29: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
      child: Text(_listData[_listCount][3]),
                            ^^^^^^^^^^
lib/main.dart:250:31: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        assetPath = _listData[_listCount][6];
                              ^^^^^^^^^^
lib/main.dart:250:9: Error: The setter 'assetPath' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing setter, or defining a setter or field named 'assetPath'.
        assetPath = _listData[_listCount][6];
        ^^^^^^^^^
lib/main.dart:251:32: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        _listCount = _listData[_listCount][2]-1;
                               ^^^^^^^^^^
lib/main.dart:251:9: Error: The setter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing setter, or defining a setter or field named '_listCount'.
        _listCount = _listData[_listCount][2]-1;
        ^^^^^^^^^^
lib/main.dart:255:15: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        print(_listCount);
              ^^^^^^^^^^
lib/main.dart:263:29: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
      child: Text(_listData[_listCount][5]),
                            ^^^^^^^^^^
lib/main.dart:266:31: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        assetPath = _listData[_listCount][7];
                              ^^^^^^^^^^
lib/main.dart:266:9: Error: The setter 'assetPath' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing setter, or defining a setter or field named 'assetPath'.
        assetPath = _listData[_listCount][7];
        ^^^^^^^^^
lib/main.dart:267:32: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        _listCount = _listData[_listCount][4]-1;
                               ^^^^^^^^^^
lib/main.dart:267:9: Error: The setter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing setter, or defining a setter or field named '_listCount'.
        _listCount = _listData[_listCount][4]-1;
        ^^^^^^^^^^
lib/main.dart:269:15: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
        print(_listCount);
              ^^^^^^^^^^
lib/main.dart:281:31: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
      content: Text(_listData[_listCount][1]),
                              ^^^^^^^^^^
lib/main.dart:316:37: Error: The getter 'assetPath' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'assetPath'.
                  image: AssetImage(assetPath),
                                    ^^^^^^^^^
lib/main.dart:336:42: Error: The getter '_listCount' isn't defined for the class '_ListFromCSVState'.
 - '_ListFromCSVState' is from 'package:example/main.dart' ('lib/main.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named '_listCount'.
                          Text(_listData[_listCount][0]),
                                         ^^^^^^^^^^

How do I pass data to class ‘_ListFromCSVState’? Note that in the original version of the code, I define these variables in this class. And everything works. But I need the value of this data to be taken from the main screen.

Thanks in advance.

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