错误：无法将“AppStateNotifier”类型的值分配给“Widget”类型的变量

Question

按照本教程。https://itnext.io/app-theming-in-flutter-dark-mode-light-mode-27d9adf3cee

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  SystemChrome.setPreferredOrientations([
    DeviceOrientation.portraitUp,
    DeviceOrientation.portraitDown,
  ]);
  runApp(
    ChangeNotifierProvider<AppStateNotifier>(
      builder: (context) => AppStateNotifier(), //<--COMPILER ERROR, details below.
      child: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return Consumer<AppStateNotifier>(
      builder: (context, appState, child) {
        return MaterialApp(
          title: 'Lockify',
          debugShowCheckedModeBanner: false,
          theme: AppTheme.lightTheme, 
          darkTheme:
              AppTheme.darkTheme, 
          home: MyHomePage(),
          themeMode: appState.isDarkModeOn ? ThemeMode.dark : ThemeMode.light,
        );
      },
    );
  }
}

错误：编译器消息：lib/main.dart:16:29：错误：“AppStateNotifier”类型的值无法分配给“Widget”类型的变量。

• “AppStateNotifier”来自“package:lockify/appstatenotifier.dart”（“lib/appstatenotifier.dart”）。
• “小部件”来自“package:flutter/src/widgets/framework.dart”（“../../Developer/flutter/packages/flutter/lib/src/widgets/framework.dart”）。构建器：（上下文）=> AppStateNotifier()，

lib/main.dart:16:16: 错误：无法将参数类型“Widget Function(BuildContext)”分配给参数类型“Widget Function(BuildContext, Widget)”。

• “小部件”来自“package:flutter/src/widgets/framework.dart”（“../../Developer/flutter/packages/flutter/lib/src/widgets/framework.dart”）。
• “BuildContext”来自“package:flutter/src/widgets/framework.dart”（“../../Developer/flutter/packages/flutter/lib/src/widgets/framework.dart”）。构建器：（上下文）=> AppStateNotifier()，

Answer 1

尝试在小部件上更改builder为。createChangeNotifierProvider