Riverpodとは
状態管理ライブラリです。
Providerの種類
種類 |
説明 |
Provider |
定数 |
StateProvider |
変数・標準 |
ScopedProvider |
出力を指定する |
StateNotifierProvider |
メソッド付き |
FutureProvider |
Future版 |
StreamProvider |
Stream版 |
ChangeNotifierProvider |
ChangeNotifierを使う |
Consumerの種類
種類 |
説明 |
Consumer |
Widgetに埋め込む |
ConsumerWidget |
StatelessWidgetのRiverpod版 |
ConsumerStatefulWidget |
StatefulWidgetのRiverpod版 簡単に実装できるが、パフォーマンスはあまりよくない |
表示方法
ConsumerWidget
- ステータスが更新されるたびに画面全体がリロードされてしまう。
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'provider.dart';
void main() {
runApp(
// Adding ProviderScope enables Riverpod for the entire project
const ProviderScope(child: MyApp()),
);
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends ConsumerWidget {
MyHomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context, WidgetRef ref) {
print("MyHomePage rebuild");
return Scaffold(
appBar: AppBar(
title: Text(ref.watch(titleProvider)),
),
body: Center(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
ref.watch(messageProvider)
),
Text(
// ref.watch(countProvider.state).state.toString()
// ref.watch(countProvider).toString()
// ref.watch(countProvider.notifier).state.toString()
ref.watch(countProvider.state).state.toString(),
style: Theme.of(context).textTheme.headline4,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: () => ref.watch(countProvider.state).state ++,
tooltip: 'Increment',
child: const Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
import 'package:flutter_riverpod/flutter_riverpod.dart';
final titleProvider = Provider<String>((ref) {
return 'Riverpod Demo Home Page';
});
final messageProvider = Provider<String>((ref) => 'テストテストテストメッセージが入ります');
final countProvider = StateProvider<int>((ref) => 1);
Consumer
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'provider.dart';
void main() {
runApp(
// Adding ProviderScope enables Riverpod for the entire project
const ProviderScope(child: MyApp()),
);
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
MyHomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
print("MyHomePage rebuild");
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Consumer(
builder: (BuildContext context, WidgetRef ref, Widget? child) => Text(
ref.watch(titleProvider)
),
),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Consumer(
builder: (context, ref, child) => Text(
ref.watch(messageProvider)
),
),
Consumer(
builder: (BuildContext context, WidgetRef ref, Widget? child) {
return Text(
// ref.watch(countProvider.state).state.toString()
// ref.watch(countProvider).toString()
// ref.watch(countProvider.notifier).state.toString()
ref.watch(countProvider.state).state.toString(),
style: Theme.of(context).textTheme.headline4,
);
}),
],
),
),
floatingActionButton: Consumer(
builder: (context, ref, child) {
print('button rebuild');
return FloatingActionButton(
onPressed: () => ref.read(countProvider.state).state ++,
tooltip: 'Increment',
child: const Icon(Icons.add),
);
},
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}