在"BlocBuilder“中使用"MultiBlocProvider”时会出现错误
我是新来的颤音.I尝试谷歌，但我不能解决我的问题。我使用"MultiBlocProvider“来管理统计数据。我想改变黑暗模式的状态，就像低音一样。
ThemeCubit.dart
part 'theme_state.dart';
class ThemeCubit extends HydratedCubit<ThemeState> {
ThemeCubit() : super(ThemeState(AppThemes.lightTheme));
void getTheme(ThemeState state) {
emit(state);
}
@override
ThemeState? fromJson(Map<String, dynamic> json) {
return json['isDark'] as bool
? ThemeState(AppThemes.darkTheme)
: ThemeState(AppThemes.lightTheme);
}
@override
Map<String, bool>? toJson(ThemeState state) {
return {'isDark': state.themeData.brightness == Brightness.dark};
}
}ThemeState.dart
part of 'theme_cubit.dart';
@immutable
class ThemeState extends Equatable {
final ThemeData themeData;
const ThemeState(this.themeData);
@override
List<Object?> get props => [themeData];
}main.dart
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MultiBlocProvider(
providers: [
BlocProvider(
lazy: true,
create: (context) => ThemeCubit(),
),
],
child:BlocBuilder<ThemeCubit, ThemeState>(
builder: (context,state) {
return MaterialApp(
debugShowCheckedModeBanner: false,
title: 'Flutter Production Boilerplate',
theme: state.themeData, //ThemeMode.dark,
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
},
),
);
}
}settingScreen.dart
Positioned(
top: 60 - widget.offset / 2,
left: 20,
child: Builder(builder: (context) {
return Switch(
value:newValue ,
onChanged: (value) {
BlocProvider.of<ThemeCubit>(context).getTheme(ThemeState(
newValue ? AppThemes.darkTheme : AppThemes.lightTheme));
});
})
),当使用"BlocProvider“时，此代码工作正常。但是当我使用"MultiBlocProvider“时，我会发现错误很严重。
将以下断言附加到呈现树上：‘package:flutter/src/widgets/Frawork.dart’：Failed断言:第4357行pos 14：'owner!._debugCurrentBuildTarget == this'：不是真。
断言指示框架本身中的错误，或者我们应该在此错误消息中提供更多的信息，以帮助您确定和修复根本原因。在这两种情况下，请通过在GitHub上提交一个bug来报告这一断言：
https://github.com/flutter/flutter/issues/new?template=2_bug.md
当抛出异常时，这是堆栈：#2 Element.rebuild。(package:flutter/src/widgets/framework.dart:4357:14) #3 Element.rebuild #4 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:4643:5) #5 ComponentElement.mount #6 Element.inflateWidget (package:flutter/src/widgets/framework.dart:3673:14) #7 (package:flutter/src/widgets/framework.dart:3425:18) #8 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:1198:16) #9 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:1167:5) #10 RenderObjectToWidgetAdapter.attachToRenderTree.(package:flutter/src/widgets/binding.dart:1112:18) #11 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2573:19) #12 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:1111:13) #13 WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:944:7) #14 WidgetsBinding.scheduleAttachRootWidget。(package:flutter/src/widgets/binding.dart:924:7) (从类_AssertionError、类_RawReceivePortImpl、类_Timer、dart:异步和dart:异步修补程序中删除13帧)
我怎么才能修好它？
回答 1
Stack Overflow用户
发布于 2021-11-28 11:44:59
我在ThemeCubit.dart中添加了以下代码：
bool isDarkMode = false;
ThemeMode currentTheme(){
isDarkMode?_setTheme(ThemeMode.dark) : _setTheme(ThemeMode.light);
return isDarkMode?ThemeMode.dark : ThemeMode.light;
}
void updateTheme(bool isDarkMode) {
this.isDarkMode = isDarkMode;
}并更改main.dart：
Widget build(BuildContext context) {
return MultiBlocProvider(
providers: [
BlocProvider(
create: (context) => ThemeCubit(),
),
],
child:ElderlyApp(),
);
}
class ElderlyApp extends StatefulWidget {
const ElderlyApp({Key? key,}) : super(key: key);
@override
_ElderlyAppState createState() => _ElderlyAppState();
}
class _ElderlyAppState extends State<ElderlyApp> with WidgetsBindingObserver {
@override
void initState() {
WidgetsBinding.instance!.addObserver(this);
super.initState();
}
@override
void didChangePlatformBrightness() {
context.read<ThemeCubit>().currentTheme();
super.didChangePlatformBrightness();
}
@override
void dispose() {
WidgetsBinding.instance!.removeObserver(this);
super.dispose();
}
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Production Boilerplate',
theme: AppThemes.lightTheme,
darkTheme: AppThemes.darkTheme,
themeMode: context.select(
(ThemeCubit cubit) => cubit.currentTheme()), //ThemeMode.dark,
debugShowCheckedModeBanner: false,
home: const MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}和更改seetingScreen.dart中的代码
Positioned(
top: 60 - widget.offset / 2,
left: 20,
child: Builder(builder: (context) {
bool isDark = context.select((ThemeCubit themeCubit) =>
themeCubit.state.themeMode) ==ThemeMode.dark ? true: false;
return Switch(
value: context.read<ThemeCubit>().isDarkMode,
onChanged: (value) {
context.read<ThemeCubit>().updateTheme(value);
});
})),https://stackoverflow.com/questions/70142045
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