flutter_bloc 库中的存储库提供程序在推送新路由时不提供存储库
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【中文标题】flutter_bloc 库中的存储库提供程序在推送新路由时不提供存储库【英文标题】:Repository provider in the flutter_bloc library doesn't provide repository with when pushing new route 【发布时间】:2020-01-25 22:58:14 【问题描述】:我正在使用 flutter_bloc 库来构建我的应用程序。除了 BlocProvider,我还在使用 Repository Provider,因为我将在整个应用程序中广泛使用特定的存储库。但是我在 context 方面遇到了问题。以下是我的代码的 sn-ps:
main.dart
void main() async
.......
appRepository _appRepository = AppRepository();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((_)
runApp(
BlocProvider(
builder: (context) =>
AuthenticationBloc(appRepository: _appRepository)..dispatch(AppStarted()),
child: App(appRepository: _appRepository,),
),
);
);
class App extends StatelessWidget
............
@override
Widget build(BuildContext context)
return MaterialApp(
debugShowCheckedModeBanner: false,
home: BlocBuilder<AuthenticationBloc, AuthenticationState>(
builder: (BuildContext context, AuthenticationState state)
.....
if (state is AuthenticationUnauthenticated)
return SafeArea(
top: false,
bottom: false,
child: RepositoryProvider(
builder: (context) => _appRepository,
child: LoginPage(firebaseMessaging: _firebaseMessaging),
),
);
......
,
),
);
登录表单中的注册按钮:
register_button.dart
class RegisterButton extends StatelessWidget
final FirebaseMessaging _firebaseMessaging;
RegisterButton(
Key key,
@required FirebaseMessaging firebaseMessaging,
) : assert(firebaseMessaging != null),
_firebaseMessaging = firebaseMessaging,
super(key: key);
@override
Widget build(BuildContext context)
return Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("Don't have an account?", style: TextStyle(color: Colors.black)),
SizedBox(width: 4.0),
GestureDetector(
child: Text("Register here!",
style: TextStyle(
color: Color(0xFF585B8D), fontWeight: FontWeight.w500)),
onTap: ()
Navigator.of(context).push(
MaterialPageRoute(builder: (context)
return RegisterPage(
firebaseMessaging: _firebaseMessaging,
);
),
);
,
)
],
);
register_page.dart
class RegisterPage extends StatelessWidget
final FirebaseMessaging _firebaseMessaging;
RegisterPage(
Key key,
@required FirebaseMessaging firebaseMessaging,
) : assert(firebaseMessaging != null),
_firebaseMessaging = firebaseMessaging,
super(key: key);
@override
Widget build(BuildContext context)
return Scaffold(
body: BlocProvider(
builder: (context) => RegisterBloc(
appRepository: RepositoryProvider.of<AppRepository>(context),
firebaseMessaging: _firebaseMessaging,
),
child: RegisterForm(),
),
);
问题:
当我点击登录表单上的注册按钮时,我收到一条错误消息:
No ancestor could be found starting from the context that was passed to RepositoryProvider.of<AppRepository>().
This can happen if:
1. The context you used comes from a widget above the RepositoryProvider.
2. You used MultiRepositoryProvider and didn't explicity provide the RepositoryProvider types.
Good: RepositoryProvider<AppRepository>(builder: (context) => AppRepository())
Bad: RepositoryProvider(builder: (context) => AppRepository()).
The context used was: BlocProvider<RegisterBloc>(dirty, state: _DelegateWidgetState#a87b2(lifecycle state: created))
为什么会出现此错误?如果我将存储库提供程序作为 blocprovider 的子项,并将应用程序作为主函数中的子存储库提供程序,然后在 App() 中删除单个存储库提供程序,则此问题似乎已解决。我猜问题是从按钮推送材料页面路径。我认为我不了解上下文或提供程序在 Flutter 中的确切工作方式。我认为提供商会查找存储库/块的小部件树,推送路由是否会破坏这种连续性?
【问题讨论】:
【参考方案1】:当您使用Navigator.of(context).push
或Navigator.of(context).pushNamed
时,推送的小部件不是调用Navigator.of(context).push
或Navigator.of(context).pushNamed
的小部件的子级,此小部件是包含给定的Navigator
的最近实例的子级context
,在你的情况下,Navigator
是由MaterialApp
创建的,所以如果你想将Repository
或Bloc
提供给不同的routes
,Provider
必须是@ 的父级987654333@,在你的情况下必须是MaterialApp
的父母。
【讨论】:
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