错误:在使用ScopedModel (上下文)时找不到正确的ScopedModel.of<MyModel>
错误:在使用ScopedModel (上下文)时找不到正确的ScopedModel.of<MyModel>
提问于 2019-04-26 07:13:45
作为一个研究颤振状态管理的局外人，我喜欢使用scoped_model进行状态管理的想法，就像flutter.dev中推荐的那样。我正在重新编写计数器应用程序。我能够使用ScopedModelDescendant<CounterModel>访问模型属性，但是我在使用ScopedModel.of<CounterModel>(context)访问模型属性时遇到了困难。有人能告诉我我可能做错了什么吗？我有一种预感，它可能是ScopedModel在我的小部件树中的位置。下面是我的代码和错误信息。
main.dart
import 'package:flutter/material.dart';
import 'package:scoped_model/scoped_model.dart';
import 'package:second/model/counter_model.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Widget build(context) {
return ScopedModel(
model: new CounterModel(),
child: Scaffold(
appBar: AppBar(
title: Text('ScopedModel'),
),
body: ScopedModelDescendant<CounterModel>(
builder: (context, child, value) {
return Text("Pressed ${value.counter} times");
},
),
floatingActionButton: buildFab1()),
);
}
Widget buildFab1() {
return ScopedModelDescendant<CounterModel>(
builder: (context, child, model) => FloatingActionButton(
child: Icon(Icons.add),
onPressed: model.incrementCounter,
),
);
}
Widget buildFab2(BuildContext context) {
return FloatingActionButton(
child: Icon(Icons.add),
onPressed: ScopedModel.of<CounterModel>(context).incrementCounter,
);
}
}model/counter_model.dart
import 'package:scoped_model/scoped_model.dart';
class CounterModel extends Model {
int _counter = 0;
int get counter => _counter;
void incrementCounter() {
_counter++;
notifyListeners();
}
}在main.dart中，如果使用buildFab2(context)而不是buildFab1()，则会出现以下错误
flutter: The following ScopedModelError was thrown building ScopedModelDescendant<Model>(dirty):
flutter: Error: Could not find the correct ScopedModel.
flutter:
flutter: To fix, please:
flutter:
flutter: * Provide types to ScopedModel<MyModel>
flutter: * Provide types to ScopedModelDescendant<MyModel>
flutter: * Provide types to ScopedModel.of<MyModel>()
flutter: * Always use package imports. Ex: `import 'package:my_app/my_model.dart';
flutter:我看了几个这样的问题，但都没有帮助。
回答 2
Stack Overflow用户
回答已采纳
发布于 2019-04-26 09:37:08
是的，因为您传递的context不会有ScopedModel of CounterModel。
您可以做的是将您的buildFab2封装在一个Builder小部件中，它将为您提供一个具有以CounterModel为父级的ScopedModel的context。
比如：
Builder(
builder: (context){
return buildFab2(context);
},
)你的应用程序看起来会是：
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Widget build(context) {
return ScopedModel(
model: new CounterModel(),
child: Scaffold(
appBar: AppBar(
title: Text('ScopedModel'),
),
body: ScopedModelDescendant<CounterModel>(
builder: (context, child, value) {
return Text("Pressed ${value.counter} times");
},
),
floatingActionButton: Builder(
builder: (context) {
// return buildFab1() if fab one required
return buildFab2(context);
},
),
),
);
}
Widget buildFab1() {
return ScopedModelDescendant<CounterModel>(
builder: (context, child, model) => FloatingActionButton(
child: Icon(Icons.add),
onPressed: model.incrementCounter,
),
);
}
Widget buildFab2(BuildContext context) {
return FloatingActionButton(
child: Icon(Icons.add),
onPressed: ScopedModel.of<CounterModel>(context).incrementCounter,
);
}
}希望这能帮上忙！
Stack Overflow用户
发布于 2021-01-04 17:53:56
您需要像这样在main.dart中添加作用域模型：
@override
Widget build(BuildContext context){
return ScopedModel<UserModel>(
model: UserModel(),
child: MaterialApp(
title: "Quiz Flamengo",
debugShowCheckedModeBanner: false,
home: Scaffold(
body: HomeScreen(),
)
)
);
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/55862549
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