How to get firebase realtime database data in to a list formate in flutter - flutter

Question

I am trying to retrieve data from Firebase Realtime Database into a list in Flutter using a model.I don't get snapshot.data how to get data.value. I have read several other posts about using Firebase with Flutter but have not found a clear answer.
Model class screen:
import 'package:firebase_database/firebase_database.dart';
class DataModel {
final String id;
final String name;
final String price;
final String qty;
DataModel(
{required this.id,
required this.name,
required this.price,
required this.qty});
DataModel.fromSnapshot(DataSnapshot snapshot)
: id = snapshot.key.toString(),
name = (snapshot.value as Map<String, dynamic>?)?['productName'] ?? '',
price =
(snapshot.value as Map<String, dynamic>?)?['productPrice'] ?? '',
qty = (snapshot.value as Map<String, dynamic>?)?['qty'] ?? '';
toJson() {
return {
"productName": name,
"productPrice": price,
"qty": qty,
};
}
}
Database service with Firebase query:
import 'package:firebase_database/firebase_database.dart';
import 'package:money_management/data_json_model.dart';
class DatabaseService {
static List<DataModel> getData() {
Query needsSnapshot =
FirebaseDatabase.instance.ref("Money Management").orderByKey();
// print(needsSnapshot); // to debug and see if data is returned
List<DataModel> needs = [];
Map<dynamic, dynamic> values = needsSnapshot.onValue as Map;
values.forEach((key, values) {
needs.add(DataModel.fromSnapshot(values));
});
return needs;
}
}
ListView Page:
import 'package:flutter/material.dart';
import 'package:money_management/data_json_model.dart';
import 'database_service.dart';
class ListScreen extends StatefulWidget {
const ListScreen({Key? key}) : super(key: key);
#override
State<ListScreen> createState() => _ListScreenState();
}
class _ListScreenState extends State<ListScreen> {
List<DataModel> _needs = [];
#override
void initState() {
super.initState();
_setupNeeds();
}
_setupNeeds() async {
List<DataModel> needs = DatabaseService.getData();
setState(() {
_needs = needs;
});
}
#override
Widget build(BuildContext context) {
return RefreshIndicator(
onRefresh: () => _setupNeeds(),
child: ListView.builder(
itemCount: _needs.length,
itemBuilder: (BuildContext context, int index) {
DataModel need = _needs[index];
return Column(
children: [
Text(need.id),
Text(need.name),
Text(need.price),
Text(need.qty),
],
);
}),
);
}
}

Answer 1

Try make the method getData() asynchronous and call get() of FirebaseDatabase instead:
class DatabaseService {
static Future<List<dynamic>> getData() async {
final snapshot = await FirebaseDatabase.instance
.ref("Money Management")
.orderByKey()
.get();
// print(snapshot); // to debug and see if data is returned
List<DataModel> needs = [];
Map<dynamic, dynamic> values = snapshot.value as Map;
values.forEach((key, values) {
needs.add(DataModel.fromSnapshot(values));
});
return needs;
}
}

Answer 2

you can receive data as Map<String,dynamic> in your DataModel like this:
class DataModel {
late String id;
late String name;
late String price;
late String qty;
DataModel({
required this.id,
required this.name,
required this.price,
required this.qty
});
DataModel.fromSnapshot(DataSnapshot snapshot){
Map<String, dynamic> myData= Map<String,dynamic>.from(snapshot.value as
Map);
id = snapshot.key.toString();
name = myData["productName"].toString() ?? '';
price =myData["productPrice"].toString() ?? '';
qty = myData["qty"].toString() ?? '';
}
Map<String,dynamic> toJson() {
return {
"productName": name,
"productPrice": price,
"qty": qty,
};
}
}