How to use a Checkbox to change text in fluter/dart using an array/list (troubles with onchanged/setstate)

Thanks in advance, I am fairly new to this and have followed a few tutorials and read countless posts here.

I am working on a personal project and have struck a dead end.

I wish to change text within a text widget by use of a checkbox, in essence turning it on and off. Unfortunatly what at first seemed simple has driven me insane for the last week or so, I apoligise if this has been answered but I cant find the help I need, I have found things similar but nothing has worked so far.

I'm trying to change my int vale with an onchanged and set stafe function with a list/array and an int value, i effectivly want to set the valeu from 0 to 1 then back again.

var textChange = [" could be ", " have become "];
int t = 0;

with;

onChanged: (value) {
                setState(() {
                  boxChecked = value!;
                  if (boxChecked) {
                    t = 1;
                  } else if (!boxChecked){
                    t = 0;
                  }
                  }
                );
              },

I have made sure I am extending a Stateful Widget tried seting up different functions and methods to pass through, I have tried using a material button instead of a checkbox but still hit the same issue. I have tried a few different ways to write my onset function including something as simple as [t++ or t = (d + 1) % textChange.length;] but these would ultimatly end in error once the int = >2, but I couldnt even get the value of my int to change. If I changed it manually and run the program, it works. however I ccant seem to get my onchanged and set state code to affect my array or int. I even had my original array as List, changed it to var in hopes it would make it mutable.

I hope I said that right, I am clearly missing something but ive looked at so much im just lost.

Below is the code I have used with the fat trimmed from the rest of my project. I'm using android studios with the latest updates.

Thanks for your help and time.

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'alternate text code',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'alternate text'),
    );
  }
}

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


  final String title;

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

class _MyHomePageState extends State<MyHomePage> {

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Divider(),
            Container(
              width: MediaQuery.of(context).size.width / 1.2,
              child:
              Text(
                'I am having trouble getting some code to work, i have tried '
                'a lot of things but cant work it out.'
                'I would like the check box to change the line of text below',
              ),
            ),
            Divider(),
            Container(
              width: MediaQuery.of(context).size.width / 1.2,
              child:
                ChangeText(),
            ),
            Divider(),
            Container(
              width: MediaQuery.of(context).size.width / 1.2,
              child:
              Text(
                'you' + textChange[t] + 'a App Developer.',
              ),
            ),
          ],
        ),
      ),
    );
  }
}

bool boxChecked = false;

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

  @override
  State<ChangeText> createState() => _ChangeText();
}

var textChange = [" could be ", " have become "];
int t = 0;

class _ChangeText extends State<ChangeText> {
  @override
  Widget build(BuildContext context) {
    return Expanded(
      child:
      Container(
            child: CheckboxListTile(
              title: const Text('learn Flutter', style: TextStyle(fontSize: 14),),
              value: boxChecked,
              onChanged: (value) {
                setState(() {
                  boxChecked = value!;
                  if (boxChecked) {
                    t = 1;
                  } else if (!boxChecked){
                    t = 0;
                  }
                  }
                );
              },
            ),
      ),
    );
  }
}