Why does my call to the variable give wrong results in terms of data?

Question

Compared to my previous question I managed to use the "points" variable but when I try to use it in a method it gives me a value of 0 and not that of the points

the method in the CartModel

int calculateTotal() {
  int totalPrice = 0;
  for (int i = 0; i < cartItems.length; i++) {
    totalPrice += int.parse(cartItems[i][1].toString());
  }
  return totalPrice;
}

PointsState pointsstate = pointsState();
void myMethod() {
  int punti = pointsstate.points; 
  int total = calculateTotal();
  if (punti >= total) {
    punti -= total;
    pointsstate.points = punti;
  }
}

Pointspage

class points extends StatefulWidget {
  pointsState createState() => pointsState();
}

class pointsState extends State<points> {
  int points = 0;

  int get getPunti {
    return points;
  }

  String cardHolderName = '';

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

  _loadPunti() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    setState(() {
      points = (prefs.getInt('points') ?? 0);
    });
  }

  _savePunti() async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setInt('points', points);
  }
  @override
  Widget build(BuildContext context) {
    Device.screenType == ScreenType.tablet;
    return SizedBox(
      width: 100.w,
      height: 100.5.h,
      child: SizedBox(
        width: 100.w,
        height: 20.5.h,
        child: Scaffold(
          appBar: AppBar(
            backgroundColor: Colors.transparent,
            elevation: 0,
            centerTitle: false,
          ),
                        OutlinedButton.icon(
                          label: Text('ricevi',
                              style: GoogleFonts.notoSerif(
                                  fontWeight: FontWeight.bold)),
                          icon: Icon(
                            Icons.money,
                            color: Colors.green[200],
                          ),
                          style: OutlinedButton.styleFrom(
                              primary: Colors.white,
                              backgroundColor: Colors.blueGrey[900]),
                          onPressed: () async {
                       
                            await Future.delayed(
                                Duration(seconds: 60)); // attendi 1 minuto
                            setState(() {
                              punti += 3;
                            });
                            _savePunti();
                            
                          },
                        ),
                      ],
                    ),
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

the points variable when used in mymethod is taken as a value of 0 but in reality it should have the value updated after each setstate in the parent class i.e. PointsPage