如何使用颤扑Riverpod像一个ChangeNotifierProxy提供程序?

Question

只是想知道是否有任何方法使用Riverpod包的方式，它的工作方式像ChangeNotifierProxy提供程序。我已经做了这个简单的代码，其中"MySecondClass"当MyFirstClass"更改其属性。在'MySecondClass'是一个方法，使用数据/变量从'MyFirstClass'当它已经改变。

到目前为止，当我按下按钮和onPressed函数被执行，'MySecondClass'更新一次，但保持不变，即使我再次按下按钮。

这是提供程序和类的部分:

void main() {
runApp(
ProviderScope(
child: MyApp(),
),
);
}
final firstClassProvider = ChangeNotifierProvider((ref) => MyFirstClass());
final secondClassProvider = ChangeNotifierProvider<MySecondClass>(
(ref) => MySecondClass(MyFirstClass().myFirstNumber));
class MyApp extends ConsumerWidget {
@override
Widget build(BuildContext context, ScopedReader watch) {
final firstClassNotifier = watch(firstClassProvider);
final secondClassNotifier = watch(secondClassProvider);
return MaterialApp(...

class MyFirstClass extends ChangeNotifier {
int _myFirstNumber = 10;
void increaseMyFirstNumber() {
_myFirstNumber = _myFirstNumber + 1;
notifyListeners();
}
get myFirstNumber => _myFirstNumber;
}
class MySecondClass extends ChangeNotifier {
MySecondClass(this.data);
final int data;
int _mySecondNumber = 2;
void receiveNumberFromClass1() {
_mySecondNumber = data;
print('$data Data');
notifyListeners();
}
get mySecondNumber => _mySecondNumber;
}

如果你想复制这个例子的整个代码，它是:

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/all.dart';
import 'package:riverpod/riverpod.dart';
import 'package:riverpod/all.dart';
void main() {
runApp(
ProviderScope(
child: MyApp(),
),
);
}
final firstClassProvider = ChangeNotifierProvider((ref) => MyFirstClass());
final secondClassProvider = ChangeNotifierProvider<MySecondClass>(
(ref) => MySecondClass(MyFirstClass().myFirstNumber));
class MyApp extends ConsumerWidget {
@override
Widget build(BuildContext context, ScopedReader watch) {
final firstClassNotifier = watch(firstClassProvider);
final secondClassNotifier = watch(secondClassProvider);
return MaterialApp(
home: Scaffold(
body: Container(
color: Colors.blueGrey,
alignment: Alignment.center,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Text(
firstClassNotifier._myFirstNumber.toString(),
style: TextStyle(fontSize: 40),
),
Text(secondClassNotifier.mySecondNumber.toString()),
MaterialButton(
child: Container(
height: 50,
width: 50,
color: Colors.deepOrangeAccent,
),
onPressed: () {
firstClassNotifier.increaseMyFirstNumber();
secondClassNotifier.receiveNumberFromClass1();
}),
],
),
),
),
);
}
}
class MyFirstClass extends ChangeNotifier {
int _myFirstNumber = 10;
void increaseMyFirstNumber() {
_myFirstNumber = _myFirstNumber + 1;
notifyListeners();
}
get myFirstNumber => _myFirstNumber;
}
class MySecondClass extends ChangeNotifier {
MySecondClass(this.data);
final int data;
int _mySecondNumber = 2;
void receiveNumberFromClass1() {
_mySecondNumber = data;
print('$data Data');
notifyListeners();
}
get mySecondNumber => _mySecondNumber;
}

Answer 1

在做了一些研究和测试之后，我找到了一个方法。我不确定这是不是你应该做的。但到目前为止，它运行良好。这是我添加的代码:

final firstClassProvider = ChangeNotifierProvider((ref) => MyFirstClass());
final secondClassProvider = ChangeNotifierProvider<MySecondClass>((ref) {
final secondClass = MySecondClass(MyFirstClass().myFirstNumber);
return secondClass;
});

class MySecondClass extends ChangeNotifier {
MySecondClass(this.data);
final int data;
int _mySecondNumber = 2;
int _myOtherNumber = 8;
void updateClass2(number) {
_myOtherNumber = number;
print('$_myOtherNumber other Number');
}
void receiveNumberFromClass1() {
_mySecondNumber = _myOtherNumber;
print('$data Data');
notifyListeners();
}
get mySecondNumber => _mySecondNumber;
}

Answer 2

你可以使用在Riverpod providers构造函数中传递的(ref)以嵌套的方式获取其他providers，类似于ChangeNotifierProxyProvider所允许的。

final provider = Provider((ref) {
final repository = ref.watch(repositoryProvider);  // use ref to obtain other providers
return SomeValue(repository);
})

来源:官方Riverpod文档