I can't pass the variable why?flutter

Question

I have tried in many ways to pass the variable points but I can not use it in another class below I leave the basic code.the variable in question is points which is located in the pointspage and I would like to use it in cartpage

CartPage

class CartPage extends StatefulWidget {
 

  _CartPagestate createState() => _CartPagestate();
}


class _CartPagestate extends State<CartPage> {
  @override
  Widget build(BuildContext context) {//some code...}

PointsPage

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

class _pointsState extends State<cubox> {
  int points = 0;

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

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

  _savePunti() async {
    
  SharedPreferences prefs = await SharedPreferences.getInstance();
    prefs.setInt('points', points);
  }

  @override
  Widget build(BuildContext context) { // some code...}

the variable in question is points which is located in the pointspage and I would like to use it in cartpage. the cartpage also has a cardmodel I would like to use the points variable to make "purchases" but I can't.

Cartmodel

class CartModel extends ChangeNotifier {

  // list of items on sale
  final List _shopItems = const [
    // [ itemName, itemPrice, imagePath, color ]
    ["Avocado", "4", "assets/images/avocado.png", Colors.green],
    ["Banana", "2", "assets/images/banana.png", Colors.yellow],
    ["chicken", "12", "assets/images/chicken.png", Colors.brown],
    ["water", "1", "assets/images/water.png", Colors.blue],
    ["apple", "3", "assets/images/mela.png", Colors.red],
    ["chocolate", "3", "assets/images/broccoli.png", Colors.brown],
  ];

  final List _other = const [
    ["Avocado", "14000", "assets/images/avocado.png", Colors.orange],
    ["Banana", "2", "assets/images/banana.png", Colors.blueGrey],
    ["chicken", "12", "assets/images/chicken.png", Colors.red],
    ["water", "1", "assets/images/water.png", Colors.blue],
  ];

  // list of cart items
  final List _cartItems = [];

  get other => _other;

  get cartItems => _cartItems;

  get shopItems => _shopItems;

  // add item to cart
  void addItemToCart(int index) {
    _cartItems.add(_shopItems[index]);
    notifyListeners();
  }

  // remove item from cart
  void removeItemFromCart(int index) {
    _cartItems.removeAt(index);
    notifyListeners();
  }

  // calculate total price
  String calculateTotal() {
    double totalPrice = 0;
    for (int i = 0; i < cartItems.length; i++) {
      totalPrice += double.parse(cartItems[i][1].toString());
    }
    return totalPrice.toStringAsFixed(2);
  }
}

Do you want to access `points ` when `navigate ` or from `any place`? — Sukaina Ahmed, Mar 13 '23 at 13:05
I would like the points accumulated in the pointspage to be used as "credit" within the cartpage, i.e. when the user clicks a button like "buy" the points necessary for the purchase are subtracted, I've been trying for months — sams, Mar 13 '23 at 13:09
As in your code using `sharedPreference` is a good idea , but what is the problem with get points from `sharedPreference`? — Sukaina Ahmed, Mar 13 '23 at 13:17
when I try to import the variable it doesn't let me use it it says it doesn't exist for pointspage but in reality it exists and it is used inside the pointspage, it doesn't let me use it to create a points subtraction method — sams, Mar 13 '23 at 13:20
"Il getter 'points' non è definito per il tipo 'pointspage'. " — sams, Mar 13 '23 at 13:34
You can use it by `prefs.getInt('points')` in any page ,points in pointspage is not `a global variable`. — Sukaina Ahmed, Mar 13 '23 at 13:37

Saad · Accepted Answer · 2023-03-13T14:03:15.513

0

If you want to access a variable from another class ,make the variable static and use it by calling ClassName.VariableName in the other class.

//global value 
int globalPoints = 23;


class MyWidget extends StatefulWidget {
  MyWidget({super.key});
  // variable inside first class 
  static int counter = 1;

  @override
  State<MyWidget> createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget> {
  @override
  Widget build(BuildContext context) {
    return const Placeholder();
  }
}


class MyWidget2 extends StatefulWidget {
  const MyWidget2({super.key});

  @override
  State<MyWidget2> createState() => _MyWidget2State();
}

class _MyWidget2State extends State<MyWidget2> {
  //accessing it inside the other class 
  int counter2 = MyWidget.counter;
  @override
  Widget build(BuildContext context) {
    return const Placeholder();
  }
}

edited Mar 13 '23 at 14:03

answered Mar 13 '23 at 13:24

Saad

539
2
19

but my variable of the first widget or pointpage is inside the state if I try to use it with your method it tells me "The getter 'points' isn't defined for the type 'pointspage'. " – sams Mar 13 '23 at 13:28
do you want to pass the variable from one class to another class? – Saad Mar 13 '23 at 13:36
or a variable that can be accessed in both class (you can make it global) – Saad Mar 13 '23 at 13:37
Would making it global allow me to use it however I like? – sams Mar 13 '23 at 13:56
yes you will be able to access it anywhere – Saad Mar 13 '23 at 13:58
like this prefs.getInt('points')? – sams Mar 13 '23 at 13:58
if it is global you can simply access it by calling -- `points` – Saad Mar 13 '23 at 14:00
I'm new to flutter I don't know how to best use global variables can you give me a practical example? – sams Mar 13 '23 at 14:01
just declare it outsite the `StatefulWidget` – Saad Mar 13 '23 at 14:02
check the code there is a global variable `globalPoints` – Saad Mar 13 '23 at 14:04
but if I declare it outside the stateful it gives me an error inside the pointspage itself because I use it below the state – sams Mar 13 '23 at 14:06
this is becuase you created two `points` variables, remove the one inside the state – Saad Mar 13 '23 at 14:08
i have one points – sams Mar 13 '23 at 14:10
can you show what the error is. – Saad Mar 13 '23 at 14:11
when I try to import the "points" variable into the cartpage to then be able to use it in an elevatedbutton to be able to subtract the points necessary for the purchase, it gives me this error: "The getter 'points' isn't defined for the type 'pointspage'. Try importing the library that defines 'points', correcting the name to the name of an existing getter, or defining a getter or field named 'points'" – sams Mar 13 '23 at 14:14
you have to import the file that have `points` class inside the `cartpage` – Saad Mar 13 '23 at 14:16
Could you give me an example, I don't quite understand – sams Mar 13 '23 at 14:17
if you are using vscode click on `points ` and press `Ctrl + .` and it will give you option to import the file – Saad Mar 13 '23 at 14:17
have you seen the `imports` at the top of the page? – Saad Mar 13 '23 at 14:17
yeah they are all there – sams Mar 13 '23 at 14:18
the only option it gives me is "create field points" – sams Mar 13 '23 at 14:20
suppose your app name is `myApp` and the file that have the `points` class name is 'myPoints.dart' you have to import it like `import 'package:myApp/myPoints.dart` – Saad Mar 13 '23 at 14:23
It's already there but nothing changes – sams Mar 13 '23 at 14:35
the name of your class is `points` and the name of the variable is also `points` , change one of them – Saad Mar 13 '23 at 14:36
done, but why? it doesn't work the same – sams Mar 13 '23 at 14:41

I can't pass the variable why?flutter

1 Answers1