作为局外人研究波动状态管理,我喜欢按照flutter.dev中的建议使用scoped_model
进行状态管理的想法。我重写了正在运行的计数器应用程序。我可以使用ScopedModelDescendant<CounterModel>
访问模型属性,但是在使用ScopedModel.of<CounterModel>(context)
访问模型属性时遇到麻烦。有人可以建议我可能做错了什么吗?我有一种预感,那就是ScopedModel
在我的小部件树中的位置。我的代码和错误消息如下。
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,如果我使用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:
我看了一些SO问题,但是没有一个帮助。
答案 0 :(得分:1)
是的,因为您通过的context
不会有ScopedModel
的{{1}}。
您可以做的是将CounterModel
包装在buildFab2
小部件中,该小部件将为您提供Builder
,其中context
以ScopedModel
为父。 / p>
赞:
CounterModel
您的应用将如下所示:
Builder(
builder: (context){
return buildFab2(context);
},
)
希望有帮助!
答案 1 :(得分:0)
您需要像这样在 main.dart 中添加 scoppedmodel:
@override
Widget build(BuildContext context){
return ScopedModel<UserModel>(
model: UserModel(),
child: MaterialApp(
title: "Quiz Flamengo",
debugShowCheckedModeBanner: false,
home: Scaffold(
body: HomeScreen(),
)
)
);
}