带有模板的 Flutter 包提供程序

Question

I'm trying to use provider with template, but Provider.of seems not working like that.

Logs:

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ The following ProviderNotFoundError was thrown building MyChildWidget(dirty): Error: Could not find the correct Provider above this MyChildWidget Widget

To fix, please:

• Ensure the Provider is an ancestor to this MyChildWidget Widget
• Provide types to Provider
• Provide types to Consumer
• Provide types to Provider.of()
• Always use package imports. Ex: `import 'package:my_app/my_code.dart';
• Ensure the correct context is being used.

Do you know any solution ?

Sample to show the problem:

import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Provider<MyChildState>.value(
          value: MyChildState("Hello world !"),
          child: MaterialApp(
            home: MyChildWidget(),
          )),
    );
  }
}

abstract class MyParentWidget<State extends MyParentState> extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final State state = Provider.of(context);
    return Text(state.text);
  }
}

abstract class MyParentState {
  final String text;

  MyParentState(this.text);
}

class MyChildWidget<MyChildState> extends MyParentWidget{
}

class MyChildState extends MyParentState {
  MyChildState(String text) : super(text);
}

Answer 1

At a first glance over your code, I can see that you are passing MyChildState("Hello world !") as the value, but later in MyParentWidget class you are requesting a State object final State state = Provider.of(context); .

Try requesting MyChildState instead of State .

My first impression after reading your code is that you are coming from a different programming language and now you are trying Flutter. A friendly advice would be keep everything as simple as possible .

All the abstraction and how the code is organized might confuse you later when you review the code you wrote instead of helping you.