[英]BlocProvider.of() called with a context that does not contain a Bloc/Cubit of type WeatherBloc
[英]BlocProvider.of() called with a context that does not contain a Bloc/Cubit of type MyBloc
我嘗試使用 BlocProvider 添加 MyBloc,但遇到了上下文問題。 錯誤如下:
Launching lib\main.dart on sdk gphone x86 arm in debug mode... lib\main.dart:1 √ Built build\app\outputs\flutter-apk\app-debug.apk. 在 ws://127.0.0.1:64346/zfCDazZFoQI=/ws 連接到 VM 服務
════════ Exception caught by gesture ═══════════════════════════════════════════
The following assertion was thrown while handling a gesture:
BlocProvider.of() called with a context that does not contain a Bloc/Cubit of type MyBloc.
No ancestor could be found starting from the context that was passed to BlocProvider.of<MyBloc>().
This can happen if the context you used comes from a widget above the BlocProvider.
The context used was: BlocAddPage(state: _BlocAddPageState#43fc1)
When the exception was thrown, this was the stack
#0 BlocProvider.of
package:flutter_bloc/src/bloc_provider.dart:121
#1 _BlocAddPageState.build.<anonymous closure>
package:example/…/examples/bloc_add.dart:53
#2 _InkResponseState._handleTap
package:flutter/…/material/ink_well.dart:993
#3 _InkResponseState.build.<anonymous closure>
package:flutter/…/material/ink_well.dart:1111
#4 GestureRecognizer.invokeCallback
我有以下 UI class。
class BlocAddPage extends StatefulWidget {
BlocAddPage({Key key}) : super(key: key);
static const routeName = '/addBloc';
@override
_BlocAddPageState createState() => _BlocAddPageState();
}
class _BlocAddPageState extends State<BlocAddPage> {
final Repository repository = Repository();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'Add',
),
),
body: BlocProvider<MyBloc>(
create: (context) => MyBloc(
repository: context.read<Repository>(),
child: ElevatedButton(
onPressed: () {
BlocProvider.of<MyBloc>(context)
.add(AddEvent());
},
child: const Text('Submit'),
style: ElevatedButton.styleFrom(
padding: EdgeInsets.all(15),
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(
Radius.circular(40),
),
),
)),
問題是你的上下文。 用Builder
包裝。
原因:當調用BlocProvider.of<MyBloc>(context)
時of
希望你的context
位於提供者之下。 但在您的情況下,上下文是_BlocAddPageState
的上下文,它是提供者的祖先。 於是我找了一個builder來解決它。
class BlocAddPage extends StatefulWidget {
BlocAddPage({Key key}) : super(key: key);
static const routeName = '/addBloc';
@override
_BlocAddPageState createState() => _BlocAddPageState();
}
class _BlocAddPageState extends State<BlocAddPage> {
final Repository repository = Repository();
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(
'Add',
),
),
body: BlocProvider<MyBloc>(
create: (context) => MyBloc(
repository: context.read<Repository>(),
child: Builder( // this!!!
builder: (context) => ElevatedButton(
onPressed: () {
BlocProvider.of<MyBloc>(context)
.add(AddEvent());
},
child: const Text('Submit'),
style: ElevatedButton.styleFrom(
padding: EdgeInsets.all(15),
shape: const RoundedRectangleBorder(
borderRadius: BorderRadius.all(
Radius.circular(40),
),
),
))),
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