Icon value not updating with provider and sqflite in flutter - flutter

Question

I was making a simple cart app, it did well but cart count not showing when app is closed and reopened again.
I am using provider and calls fetchCartProducts() method when the app is opened. It calls fine. but cart badge widget itemcount is not changing at first time. only shows 0 at first time.
Future<void> fetchCartProducts() async {
final dataList = await DBHelper.getData('cart_food');
//convert dataList to _cartItems
final entries = dataList
.map((item) => CartModel(
item['id'],
item['price'].toDouble(),
item['productName'],
item['quantity'],
))
.map((cart) => MapEntry(cart.id, cart));
_cartItems = Map<String, CartModel>.fromEntries(entries);
print('inside fetchcart');
}
class HomeScreen extends StatefulWidget
{
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen>
{
Future<List<FoodItem>> _foodItems;
var _isInit = true;
#override
void initState() {
super.initState();
_foodItems = ApiService.getFoodItems();
Provider.of<CartProvider>(context, listen: false).fetchCartProducts();
setState(() {});
}
#override
void didChangeDependencies()
{
if (_isInit) {
Provider.of<CartProvider>(context).fetchCartProducts();
_isInit = false;
setState(() {});
}
super.didChangeDependencies();
}
#override
Widget build(BuildContext context) {
final cart = Provider.of<CartProvider>(context, listen: false);
return Scaffold(
appBar: AppBar(
title: const Text('Food Cart'),
actions: [
//this is not updating when the app is closed and opened again.
Consumer<CartProvider>(
builder: (_, cartprovider, ch) => Badge(
child: ch,
value: cartprovider.itemCount.toString(),
),
child: IconButton(
icon: Icon(Icons.shopping_cart),
onPressed: () {
Navigator.push(
context,
MaterialPageRoute(builder: (_) {
return CartScreen();
}),
);
},
),
),
],
),
body: FutureBuilder<List<FoodItem>>(
future: _foodItems,
builder: (conext, snapshot) => !snapshot.hasData
? const Center(
child: CircularProgressIndicator(),
)
: ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (context, index) {
FoodItem foodItem = snapshot.data[index];
return ListTile(
title: Text(foodItem.productName),
subtitle: Text(foodItem.variant),
trailing: IconButton(
onPressed: () {
cart.addToCart(
foodItem.storeid.toString(),
foodItem.productName,
1,
foodItem.price,
);
setState(() {});
},
icon: const Icon(Icons.shopping_cart),
),
);
},
),
),
);
}
}
otherwise when item added to cart, it working fine. the data loss when reopened. how to get total count when the app starts?

Answer 1

In order to rebuild Consumer you need to call notifyListeners() inside your CartProvider
Add notifyListeners() to your fetchCartProducts() after assigning the value to _cartItems = Map<String, CartModel>.fromEntries(entries);
Future<void> fetchCartProducts() async {
final dataList = await DBHelper.getData('cart_food');
//convert dataList to _cartItems
final entries = dataList
.map((item) => CartModel(
item['id'],
item['price'].toDouble(),
item['productName'],
item['quantity'],
))
.map((cart) => MapEntry(cart.id, cart));
_cartItems = Map<String, CartModel>.fromEntries(entries);
notifyListeners(); // <------- this line
print('inside fetchcart');
}