Why state change error occurs on flutter_riverpod during initialization - flutter

Question

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
final dataProvider = StateNotifierProvider<DataNotifier, List<int>>((ref) {
return DataNotifier();
});
class DataNotifier extends StateNotifier<List<int>> {
DataNotifier() : super([]);
Future<void> getData() async {
state = [];
await Future.delayed(const Duration(seconds: 2));
state = [1, 2];
}
}
void main() => runApp(ProviderScope(child: App()));
class App extends StatelessWidget {
#override
Widget build(BuildContext context) {
return MaterialApp(
home: Home(),
);
}
}
class Home extends StatelessWidget {
const Home({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
color: Colors.white,
child: Center(
child: ElevatedButton(
onPressed: () {
Navigator.of(context).push(
MaterialPageRoute(builder: (_) => SecondPage()),
);
},
child: const Text('Next page'),
),
),
),
);
}
}
class SecondPage extends ConsumerStatefulWidget {
const SecondPage({Key? key}) : super(key: key);
#override
_SecondPageState createState() => _SecondPageState();
}
class _SecondPageState extends ConsumerState<SecondPage> {
#override
void initState() {
super.initState();
ref.read(dataProvider.notifier).getData();
}
#override
Widget build(BuildContext context) {
final numbers = ref.watch(dataProvider);
return Scaffold(
appBar: AppBar(),
body: ListView.builder(
itemBuilder: (_, index) {
return Text('data: $index');
},
itemCount: numbers.length,
),
);
}
}
I am new to riverpod and I noticed this error while changing state.
In the above code when I tap the "next page" button at the fresh start for the first time it works as expected but when I go back and again tap the "next page" button, an error shown below is thrown:
StateNotifierListenerError (At least listener of the StateNotifier Instance of 'DataNotifier' threw an exception
when the notifier tried to update its state.
Does anyone know why this occurs and how can I prevent it.

Answer 1

You can solve the issue using autoDispose
final dataProvider = StateNotifierProvider.autoDispose<DataNotifier, List<int>>(
(ref) => DataNotifier(),
);
For Future I prefer using FutureProvider.
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