having an problem designing Provider design to flutter application - flutter

Question

The main reason i want to change the design is that when i scan a product and then scan the same one i get the same product twice while it is the same one so basically i just need to increase the quantity of the product by one.
I have used Provider before but I still can't manage to arrange the classes the right way to make it work.
first i have tried to make a Productobject(which extenes ChangeNotifier) inside ProductCard class and use provider.of(context) and retrieve the quantity of the prodcut.
plus,at the main before the material I used ChangeNotifierProvider
I have a mess in my head and i would love to see someone arranging the code with explanation of how the things works
main
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:sally_smart/utilities/product_notifier.dart';
import 'screens/checkout_screen.dart';
import 'screens/login_screen.dart';
import 'screens/registration_screen.dart';
import 'screens/welcome_screen.dart';
import 'package:provider/provider.dart';
//void main() => runApp(Sally());
void main() {
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((_) {
runApp(new Sally());
});
}
class Sally extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
theme: ThemeData.dark().copyWith(
backgroundColor: Colors.teal,
cardColor: Color(0xFF068194),
),
initialRoute: LoginScreen.id,
routes: {
WelcomeScreen.id: (context) => WelcomeScreen(),
RegistrationScreen.id: (context) => RegistrationScreen(),
LoginScreen.id: (context) => LoginScreen(),
CheckoutScreen.id: (context) => CheckoutScreen()
},
);
}
}
ProductCard
import 'package:flutter/material.dart';
import 'package:sally_smart/utilities/constants.dart';
import 'package:sally_smart/utilities/product.dart';
import 'package:sally_smart/utilities/round_icon_button.dart';
class ProductCard extends StatefulWidget {
final Product prodcut;
ProductCard(Product product);
#override
_ProductCardState createState() => _ProductCardState();
}
class _ProductCardState extends State<ProductCard> {
double finalPrice;
// static int quantity = 1;
#override
Widget build(BuildContext context) {
finalPrice = widget.prodcut.quantity * widget.prodcut.productPrice;
return Card(
elevation: 5.0,
child: ListTile(
leading: Padding(
padding: EdgeInsets.only(
left: 2.0,
),
child: Icon(
widget.prodcut.productIcon,
size: 35,
),
),
title: Text(
widget.prodcut.productName,
style: kProductNameTextStyle,
),
subtitle: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Container(
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
RoundIconButton(
icon: Icons.add,
color: Colors.green,
function: () {
setState(() {
widget.prodcut.quantity++;
});
}),
Text(
'$widget.prodcut.quantity',
),
RoundIconButton(
icon: Icons.remove,
color: Colors.red,
function: () {
setState(() {
widget.prodcut.quantity--;
if ( widget.prodcut.quantity == 0) {
widget.prodcut.quantity++;
}
});
}),
],
),
),
Text(
'${finalPrice.toStringAsFixed(2)} ₪',
style: TextStyle(fontSize: 15),
),
],
),
),
);
}
}
Prodcut
import 'package:flutter/cupertino.dart';
class Product extends ChangeNotifier{
String productName;
double productPrice;
IconData productIcon;
String id;
String barCode;
int quantity;
Product(this.productName, this.productPrice, this.productIcon, this.id,
this.barCode,this.quantity);
}
welcome screen
import 'package:audioplayers/audio_cache.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_barcode_scanner/flutter_barcode_scanner.dart';
import 'package:sally_smart/screens/login_screen.dart';
import 'package:sally_smart/screens/registration_screen.dart';
import 'package:sally_smart/utilities/constants.dart';
import 'package:sally_smart/utilities/product.dart';
import 'package:sally_smart/utilities/product_card.dart';
import 'package:sally_smart/utilities/scan_button_const.dart';
import 'package:sally_smart/utilities/scan_methods.dart';
//import 'package:sally_smart/utilities/scan_pageML.dart';
//import 'package:flutter_camera_ml_vision/flutter_camera_ml_vision.dart';
//import 'package:firebase_ml_vision/firebase_ml_vision.dart';
//working version
//List<ProductCard> shoppingList = [];
final sallyDatabase = Firestore.instance;
class WelcomeScreen extends StatefulWidget {
static const String id = 'welcome_screen';
#override
_WelcomeScreenState createState() => _WelcomeScreenState();
}
class _WelcomeScreenState extends State<WelcomeScreen> {
final _auth = FirebaseAuth.instance;
final textEditorController = TextEditingController();
String _scanBarcode = 'Unknown';
String productName = 'Product Test';
double productPrice;
String productBarCode;
IconData productIcon = Icons.add_shopping_cart;
final List<ProductCard> shoppingList = [];
int productId = 0;
static AudioCache barcodeSound = AudioCache();
// saves barcodes data
List<String> data = [];
Future<void> initPlatformState() async {
String barcodeScanRes;
// Platform messages may fail, so we use a try/catch PlatformException.
try {
barcodeScanRes =
await FlutterBarcodeScanner.scanBarcode("#ff6666", "Cancel", true);
} on PlatformException {
barcodeScanRes = 'Failed to get platform version.';
}
// If the widget was removed from the tree while the asynchronous platform
// message was in flight, we want to discard the reply rather than calling
// setState to update our non-existent appearance.
if (!mounted) return;
setState(() {
_scanBarcode = barcodeScanRes;
});
}
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Color(0xFF21bacf),
appBar: AppBar(
elevation: 3,
backgroundColor: Colors.black54,
leading: Icon(
Icons.shopping_basket,
size: 30,
),
title: Text(
'Sally',
textAlign: TextAlign.end,
style: kHeaderTextStyle,
),
actions: <Widget>[
IconButton(icon: Icon(Icons.settings), onPressed: () {}),
VerticalDivider(
color: Color(0x8CFFFFFF),
width: 3,
),
IconButton(
icon: Icon(Icons.power_settings_new),
onPressed: () {
_auth.signOut();
Navigator.pushNamed(context, LoginScreen.id);
}),
VerticalDivider(
color: Color(0x8CFFFFFF),
width: 3,
),
IconButton(icon: Icon(Icons.share), onPressed: () {}),
VerticalDivider(
color: Color(0x8CFFFFFF),
width: 3,
),
// PopupMenuButton(itemBuilder: ),
],
),
body: Container(
decoration: kBackgroundGradientScan,
child: SafeArea(
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Row(
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
Text(
'ברוכה הבאה, סאלי',
textAlign: TextAlign.right,
style: kHeaderTextStyle,
),
Padding(
padding: EdgeInsets.only(top: 5, right: 15),
child: Hero(
tag: 'Sally',
child: CircleAvatar(
backgroundImage:
AssetImage('images/missing_avatar_F.png'),
maxRadius: 25,
),
),
)
],
),
Padding(
padding: EdgeInsets.symmetric(vertical: 3, horizontal: 15),
child: TextField(
textAlign: TextAlign.center,
onChanged: (value) async {
_scanBarcode = value;
productPrice = await getProductPrice(_scanBarcode);
productName = await getProductName(_scanBarcode);
},
decoration: kTextFieldDecoration.copyWith(
prefixIcon: IconButton(
icon: Icon(Icons.search),
onPressed: () {
_scanBarcode = '';
textEditorController.clear();
try {
setState(() {
textEditorController.clear();
//checking if a product was already scanned
//adding a ProductCard to the shopping list with the ProductCard const. Works on scan
shoppingList.add(ProductCard( new Product(productName, productPrice, productIcon, shoppingList.length.toString(),
productBarCode, 1)));
});
} catch (e) {
print(e);
}
},
),
// prefix: IconButton(
// icon: Icon(Icons.search),
// onPressed: () {
//
// }),
hintText: '...הכנס ברקוד או שם מוצר ידנית'),
),
),
DividerSally(),
shoppingListBuilder(),
DividerSally(),
Container(
child: Padding(
padding: EdgeInsets.only(bottom: 15.0),
child: Padding(
padding: EdgeInsets.symmetric(horizontal: 40),
child: Column(
children: <Widget>[
ScanMainButton(
iconData: Icons.flip,
buttonText: 'סרוק מוצר',
onPressed: () async {
//Navigator.pushNamed(context, ScanScreen.id);
await initPlatformState();
barcodeSound.play('barcode_sound.mp3');
//Changes the product name by referencing to the database
productBarCode = _scanBarcode;
productPrice =
await getProductPrice(_scanBarcode);
productName =
await getProductName(_scanBarcode);
setState(() {
//checking if a product was already scanned
//adding a ProductCard to the shopping list with the ProductCard const. Works on scan
shoppingList.add(ProductCard( new Product(productName, productPrice, productIcon, shoppingList.length.toString(),
productBarCode, 1)));
});
},
color: Colors.teal,
),
ScanMainButton(
iconData: Icons.check,
buttonText: 'מעבר לתשלום',
color: Colors.green,
onPressed: () {
Navigator.pushNamed(
context, RegistrationScreen.id);
}),
],
),
),
),
)
],
),
),
),
));
}
Expanded shoppingListBuilder() {
return Expanded(
child: Container(
color: Colors.black38,
child: ListView.builder(
reverse: true,
itemCount: shoppingList.length,
itemBuilder: (context, index) {
ProductCard item = shoppingList[index];
return Dismissible(
key: Key(item.prodcut.id),
direction: DismissDirection.startToEnd,
onDismissed: (direction) {
setState(() {
shoppingList.removeAt(index);
});
},
background: Container(
child: Icon(
Icons.restore_from_trash,
size: 40,
),
margin: EdgeInsets.symmetric(vertical: 5),
decoration: BoxDecoration(
gradient: LinearGradient(
begin: Alignment.bottomLeft,
end: Alignment.topRight,
colors: [
Color(0x8C650223),
Color(0x8CB9013E),
],
stops: [0.1, 0.9],
),
),
),
child: item //ListTile(title: Text('${item.productName}.')),
);
},
),
));
}
}