颤振提供程序无法立即重新渲染

Question

这是我的源代码：https://github.com/liou-jia-hao/flutter_demo_app/tree/Cannot-refresh

我创建了一个文件，其中包含我的计数器模型；counter.dart"；，这是代码：

import 'package:flutter/foundation.dart';
import 'package:nanoid/nanoid.dart';
class Counter {
String id;
int count;
void increment() {
count++;
}
void decrement() {
count--;
}
Counter(this.id, this.count);
}
class CountersModel with ChangeNotifier {
Map<String, Counter> countersMap = {};
void createCounter() {
var id = nanoid();
countersMap[id] = Counter(id, 0);
notifyListeners();
}
}

这是我的主要零件代码：

// ignore_for_file: public_member_api_docs, lines_longer_than_80_chars
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'models/counter.dart';
/// This is a reimplementation of the default Flutter application using provider + [ChangeNotifier].
void main() {
runApp(
/// Providers are above [MyApp] instead of inside it, so that tests
/// can use [MyApp] while mocking the providers
MultiProvider(
providers: [
ChangeNotifierProvider(create: (_) => CountersModel()),
],
child: const MyApp(),
),
);
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
return MaterialApp(
themeMode: ThemeMode.dark,
theme: ThemeData(brightness: Brightness.dark),
home: const MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
const MyHomePage({Key? key}) : super(key: key);
@override
Widget build(BuildContext context) {
var countersSet = context.select<CountersModel, Set<Counter>>(
(model) => model.countersMap.values.toSet());
var countersModel = context.read<CountersModel>();
return Scaffold(
appBar: AppBar(
title: const Text('Example'),
),
body: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: countersSet.map((counter) => BlueButton(counter)).toList(),
),
),
floatingActionButton: FloatingActionButton(
key: const Key('increment_floatingActionButton'),
/// Calls `context.read` instead of `context.watch` so that it does not rebuild
/// when [Counter] changes.
onPressed: countersModel.createCounter,
tooltip: 'Increment',
child: const Icon(Icons.add),
),
);
}
}
class BlueButton extends StatelessWidget {
const BlueButton(this.counter, {Key? key}) : super(key: key);
final Counter counter;
@override
Widget build(BuildContext context) {
return ElevatedButton(
onPressed: counter.increment,
onLongPress: counter.decrement,
child: Column(
children: [Text(counter.id), Text('${counter.count}')],
),
);
}
}

我希望BlueButton上的数字能立即增加。但是BlueButton上的数字不能立即增加。

Answer 1

我认为您的计数器需要上下文才能更改按钮。看看这个答案。