How to use dynamic global list in flutter - flutter

Question

I am new to Flutter and attempting sample mutual fund app to cover all basic widgets.
Requirement -> After selecting MF scheme, when user confirms on "buyNow" screen, corresponding scheme should get added to global dynamic list in "Cart" screen. This is basically a cart which is accessible to user on any screen, similar to shopping cart. I want to update cart list on "buyNow" screen and display same on "Cart" screen.
I have followed link to learn about 'provider' method of flutter to solve this, but not able to do.
PFB code
Main.dart
void main() {
runApp(
ChangeNotifierProvider(
create: (context) => CartModel(),
child: MaterialApp(
home: Schemelist(),
routes: {
'/landing': (context) => Landing(),
'/schemelist': (context) => Schemelist(),
'/schemeBuy': (context) => SchemeBuy(),
'/buyNow': (context) => BuyNow(),
'/cart': (context) => Cart(),
},
),
),
);
}
Cartmodel.dart
import 'package:flutter/foundation.dart';
class CartModel with ChangeNotifier{
String schemeName;
String type;
String fromDate;
String toDate;
double amount;
List<CartModel> _cartList=[];
CartModel({this.amount,this.fromDate,this.schemeName,this.toDate,this.type});
void addToCart(CartModel cartObj){
_cartList.add(cartObj);
notifyListeners();
}
double get totalAmount =>
_cartList.fold(0, (total, current) => total + current.amount);
}
BuyNow.dart
RaisedButton(
onPressed: () {
_cart=new CartModel(amount:1000,fromDate:_dateTime.toString(),schemeName:widget.investmentObj.schemeName,toDate:_dateTime1.toString(),type:'SIP');
var cart = Provider.of<CartModel>(context);
cart.addToCart(_cart);
Navigator.pushNamed(context, '/cart');
},
child: Text('Yes'),
),
Cart.dart //where I will display dynamic list
Widget build(BuildContext context) {
var cart = Provider.of<CartModel>(context);
return Scaffold(
appBar: AppBar(
title: Text('Cart'),
centerTitle: true,
),
body: ListView.builder(
itemCount: --not able to access list--
itemBuilder: (context, index) => ListTile(
title: Text(
-------
),
),
),
);
}

Answer 1

First we should modify CartModel class. The fields (such as schemeName) should belong to the CartItem class, and the CartModel should only do its own thing (addToCart and others).
class CartModel with ChangeNotifier {
List<CartItem> _itemList = [];
// An unmodifiable view of the items in the cart.
UnmodifiableListView<CartItem> get itemList => UnmodifiableListView(_itemList);
void addToCart(CartItem item) {
_itemList.add(item);
notifyListeners();
}
double get totalAmount => _itemList.fold(0, (total, current) => total + current.amount);
}
class CartItem{
String schemeName;
String type;
String fromDate;
String toDate;
double amount;
CartItem({this.amount, this.fromDate, this.schemeName, this.toDate, this.type});
}
Then, in Cart.dart
Widget build(BuildContext context) {
var itemList = Provider.of<CartModel>(context).itemList;
return Scaffold(
appBar: AppBar(
title: Text('Cart'),
centerTitle: true,
),
body: ListView.builder(
itemCount: itemList.length,
itemBuilder: (_, index) {
var item = itemList[index];
return Text(item.schemeName);
},
),
);
}
You will get a error while click RaisedButton:
Tried to listen to a value exposed with provider, from outside of the widget tree.
This is likely caused by an event handler (like a button's onPressed) that called
Provider.of without passing `listen: false`.
To fix it, edit BuyNow.dart:
RaisedButton(
onPressed: () {
var _item = CartItem(amount: 1000, fromDate: _dateTime.toString(), schemeName: widget.investmentObj.schemeName, toDate: _dateTime1.toString(), type: 'SIP');
//just set listen to false
var cart = Provider.of<CartModel>(context, listen: false);
cart.addToCart(_item);
Navigator.pushNamed(context, '/cart');
},
child: Text('Yes'),
),