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main.dart
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main.dart
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import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
void main() {
runApp(const ProviderScope(child: MyApp()));
}
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatelessWidget {
MyHomePage({super.key, required this.title});
final String title;
final _mutableProvider = StateProvider<MutableData>((ref) => MutableData());
final _immutableProvider =
StateProvider<ImmutableData>((ref) => ImmutableData(0));
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const Text(
'You have pushed the button this many times:',
),
Consumer(builder: (context, ref, child) {
return Text(
'${ref.watch(_mutableProvider).count}',
style: Theme.of(context).textTheme.headline4,
);
}),
Consumer(builder: (context, ref, child) {
return Text(
'${ref.watch(_immutableProvider).count}',
style: Theme.of(context).textTheme.headline4,
);
}),
],
),
),
floatingActionButton: Consumer(builder: (context, ref, child) {
return FloatingActionButton(
onPressed: () {
final mutableData = ref.read(_mutableProvider);
mutableData.countUp();
ref.read(_mutableProvider.notifier).state = mutableData;
final oldImmutableData = ref.read(_immutableProvider);
final newImmutableData = oldImmutableData.countUp();
ref.read(_immutableProvider.notifier).state = newImmutableData;
},
tooltip: 'Increment',
child: const Icon(Icons.add),
);
}),
);
}
}
class MutableData {
int count = 0;
void countUp() {
count++;
}
}
class ImmutableData {
ImmutableData(this.count);
final int count;
ImmutableData countUp() {
return ImmutableData(count + 1);
}
}