Flutter - Provider - Clearing Data itself when navigate - flutter

Question

When I in a page and added some quantity and navigate to another page and come back to added more quantity data is cleared.
Here's my code.
add_inv_stream.dart
class AddInvStream extends StatelessWidget {
const AddInvStream({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
FirebaseServices services = FirebaseServices();
final provider = Provider.of<InventoryProvider>(context);
return StreamBuilder<QuerySnapshot>(
stream: services.inventory
.where('fishType', isEqualTo: provider.inventoryData['fishType'])
.where('status', isEqualTo: true)
.snapshots(),
builder: (context, snapshot) {
if (snapshot.hasError) {
return const Center(child: Text('Something wrong!'));
}
if (snapshot.connectionState == ConnectionState.waiting) {
return const Center(child: CircularProgressIndicator());
}
if (snapshot.data!.size == 0) {
return const Center(
child: Text('No inventories'),
);
}
return AddInvData(snapshot: snapshot, services: services);
},
);
}
}
add_inv_data.dart
class AddInvData extends StatefulWidget {
final AsyncSnapshot<QuerySnapshot<Object?>> snapshot;
final FirebaseServices services;
const AddInvData({Key? key, required this.snapshot, required this.services})
: super(key: key);
#override
State<AddInvData> createState() => _AddInvDataState();
}
class _AddInvDataState extends State<AddInvData> {
final _qty = TextEditingController();
List sellerList = [];
#override
Widget build(BuildContext context) {
final providerr = Provider.of<InventoryProvider>(context);
return ListView.builder(
padding: const EdgeInsets.all(15.0),
physics: const ScrollPhysics(),
shrinkWrap: true,
itemCount: widget.snapshot.data!.size,
itemBuilder: (context, index) {
Map<String, dynamic> sellerData =
widget.snapshot.data!.docs[index].data() as Map<String, dynamic>;
int sellerQty = int.parse(sellerData['qty']);
return InkWell(
onTap: () {
showDialog(
context: context,
useRootNavigator: false,
builder: (context) {
return Dialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(40),
),
elevation: 16,
child: Container(
padding: const EdgeInsets.all(20),
child: Column(
mainAxisSize: MainAxisSize.min,
children: [
Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
const Text('Quantity in kg: '),
const SizedBox(width: 10),
Container(
height: 60,
width: 60,
decoration: BoxDecoration(
border: Border.all(color: Colors.black),
),
child: TextFormField(
controller: _qty,
textAlign: TextAlign.center,
keyboardType: TextInputType.number,
decoration: const InputDecoration(
border: InputBorder.none,
),
),
),
],
),
const SizedBox(height: 50),
TextButton(
onPressed: () async {
Map<String, dynamic> seller = {
'date': sellerData['date'],
'qty': _qty.text,
};
sellerList.add(seller);
providerr.getData(sellerList: sellerList);
print(providerr.inventoryData['sellerList']);
Navigator.of(context).push(MaterialPageRoute(
builder: (context) => const InvDetails(),
));
},
child: const Text('ASSIGN'),
),
],
),
),
);
},
);
},
child: Padding(
padding: const EdgeInsets.fromLTRB(10, 0, 10, 30),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Text(
sellerData['date'],
style: const TextStyle(fontSize: 18),
),
Text(
'${sellerData['qty']} kg',
style: const TextStyle(fontSize: 18),
),
],
),
),
);
},
);
}
}
inv_details.dart
class InvDetails extends StatelessWidget {
const InvDetails({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: TextButton(
onPressed: () {
Navigator.of(context).push(MaterialPageRoute(
builder: (context) => const AddInv(),
));
},
child: const Text('Add Inventory'),
),
),
);
}
}
inv_provider.dart
class InventoryProvider with ChangeNotifier {
Map<String, dynamic> inventoryData = {};
getData({List? sellerList}) {
if (sellerList != null) {
inventoryData['sellerList'] = sellerList;
}
notifyListeners();
}
}
Here printing at the first
[{date: 10/31/2022, qty: 1}]
When I navigate to InvDetails from AddInvData and when the button is clicked it's printing
[{date: 11/25/2022, qty: 1}]
Data is not updating
But if I didn't navigate.
i.e If I stay in AddInvData and added quantity it is updating.
inv_data.dart (Added textbutton part only ) removed navigate
TextButton(
onPressed: () async {
Map<String, dynamic> seller = {
'date': sellerData['date'],
'qty': _qty.text,
};
sellerList.add(seller);
providerr.getData(sellerList: sellerList);
print(providerr.inventoryData['sellerList']);
},
prints
[{date: 10/31/2022, qty: 1}]
[{date: 10/31/2022, qty: 1}, {date: 11/25/2022, qty: 1}]
Why this is not hapenning when navigate and come back to previous page?