Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
现在我正在使用bloc as my flutter state manager,I define the bloc state manage file follow the docs。当我像这样使用 bloc 时：
import 'package:acientbay/src/bloc/nav/nav_bloc.dart';
import 'package:acientbay/src/page/home/home_list.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
class HomeNav extends HookWidget{
@override
Widget build(BuildContext context) {
return BlocBuilder<NavBloc, NavState>(
buildWhen: (previous, current) => previous.username != current.username,
builder: (context, state) {
return Scaffold(
body: HomeList(),
bottomNavigationBar: BottomNavigationBar(
items:[
BottomNavigationBarItem(icon: Icon(Icons.home), label: '作品库'),
BottomNavigationBarItem(icon: Icon(Icons.school), label: '我的')
],
currentIndex:state.selectNavIndex
),
);
},
);
}
}
显示错误：
Performing hot restart...
Syncing files to device sdk gphone x86 arm...
Restarted application in 952ms.
======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building HomeNav:
Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
Make sure that BlocBuilder<NavBloc, NavState> is under your MultiProvider/Provider<NavBloc>.
This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// Will throw a ProviderNotFoundError, because `context` is associated
// to the widget that is the parent of `Provider<Example>`
child: Text(context.watch<Example>()),
),
}
```
consider using `builder` like so:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// we use `builder` to obtain a new `BuildContext` that has access to the provider
builder: (context) {
// No longer throws
return Text(context.watch<Example>()),
}
),
}
```
If none of these solutions work, consider asking for help on Whosebug:
https://whosebug.com/questions/tagged/flutter
The relevant error-causing widget was:
HomeNav file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12
When the exception was thrown, this was the stack:
#0 Provider._inheritedElementOf (package:provider/src/provider.dart:332:7)
#1 Provider.of (package:provider/src/provider.dart:284:30)
#2 ReadContext.read (package:provider/src/provider.dart:610:21)
#3 _BlocBuilderBaseState.initState (package:flutter_bloc/src/bloc_builder.dart:130:36)
#4 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4711:57)
...
====================================================================================================
======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building HomeNav:
Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
Make sure that BlocBuilder<NavBloc, NavState> is under your MultiProvider/Provider<NavBloc>.
This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// Will throw a ProviderNotFoundError, because `context` is associated
// to the widget that is the parent of `Provider<Example>`
child: Text(context.watch<Example>()),
),
}
```
consider using `builder` like so:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// we use `builder` to obtain a new `BuildContext` that has access to the provider
builder: (context) {
// No longer throws
return Text(context.watch<Example>()),
}
),
}
```
If none of these solutions work, consider asking for help on Whosebug:
https://whosebug.com/questions/tagged/flutter
The relevant error-causing widget was:
HomeNav file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12
When the exception was thrown, this was the stack:
#0 Provider._inheritedElementOf (package:provider/src/provider.dart:332:7)
#1 Provider.of (package:provider/src/provider.dart:284:30)
#2 ReadContext.read (package:provider/src/provider.dart:610:21)
#3 _BlocBuilderBaseState.initState (package:flutter_bloc/src/bloc_builder.dart:130:36)
#4 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4711:57)
...
====================================================================================================
哪里出了问题，我应该怎么做才能解决？
您是否在您正在使用的小部件上方初始化了您的 NavBloc。
如果没有那么也许你可以像这样初始化它：
Scaffold(
body: BlocProvider(
create: (context) => NavBloc(),
child: ...(), // Your class goes here
),
)
只需在您的 HomeNav class 中创建一个 class NavBloc 的实例，并将其传递给 blocbuilder 的 bloc 参数。
解决方案：
class HomeNav extends HookWidget{
@override
Widget build(BuildContext context) {
final navBloc = NavBloc(); // creating an instance of the bloc class
return BlocBuilder<NavBloc, NavState>(
bloc: navBloc, // passing it here
buildWhen: (previous, current) => previous.username != current.username,
builder: (context, state) {
return Scaffold(
body: HomeList(),
bottomNavigationBar: BottomNavigationBar(
items:[
BottomNavigationBarItem(icon: Icon(Icons.home), label: '作品库'),
BottomNavigationBarItem(icon: Icon(Icons.school), label: '我的')
],
currentIndex:state.selectNavIndex
),
);
},
);
}
}
现在我正在使用bloc as my flutter state manager,I define the bloc state manage file follow the docs。当我像这样使用 bloc 时：
import 'package:acientbay/src/bloc/nav/nav_bloc.dart';
import 'package:acientbay/src/page/home/home_list.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
class HomeNav extends HookWidget{
@override
Widget build(BuildContext context) {
return BlocBuilder<NavBloc, NavState>(
buildWhen: (previous, current) => previous.username != current.username,
builder: (context, state) {
return Scaffold(
body: HomeList(),
bottomNavigationBar: BottomNavigationBar(
items:[
BottomNavigationBarItem(icon: Icon(Icons.home), label: '作品库'),
BottomNavigationBarItem(icon: Icon(Icons.school), label: '我的')
],
currentIndex:state.selectNavIndex
),
);
},
);
}
}
显示错误：
Performing hot restart...
Syncing files to device sdk gphone x86 arm...
Restarted application in 952ms.
======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building HomeNav:
Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
Make sure that BlocBuilder<NavBloc, NavState> is under your MultiProvider/Provider<NavBloc>.
This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// Will throw a ProviderNotFoundError, because `context` is associated
// to the widget that is the parent of `Provider<Example>`
child: Text(context.watch<Example>()),
),
}
```
consider using `builder` like so:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// we use `builder` to obtain a new `BuildContext` that has access to the provider
builder: (context) {
// No longer throws
return Text(context.watch<Example>()),
}
),
}
```
If none of these solutions work, consider asking for help on Whosebug:
https://whosebug.com/questions/tagged/flutter
The relevant error-causing widget was:
HomeNav file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12
When the exception was thrown, this was the stack:
#0 Provider._inheritedElementOf (package:provider/src/provider.dart:332:7)
#1 Provider.of (package:provider/src/provider.dart:284:30)
#2 ReadContext.read (package:provider/src/provider.dart:610:21)
#3 _BlocBuilderBaseState.initState (package:flutter_bloc/src/bloc_builder.dart:130:36)
#4 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4711:57)
...
====================================================================================================
======== Exception caught by widgets library =======================================================
The following ProviderNotFoundException was thrown building HomeNav:
Error: Could not find the correct Provider<NavBloc> above this BlocBuilder<NavBloc, NavState> Widget
This happens because you used a `BuildContext` that does not include the provider
of your choice. There are a few common scenarios:
- You added a new provider in your `main.dart` and performed a hot-reload.
To fix, perform a hot-restart.
- The provider you are trying to read is in a different route.
Providers are "scoped". So if you insert of provider inside a route, then
other routes will not be able to access that provider.
- You used a `BuildContext` that is an ancestor of the provider you are trying to read.
Make sure that BlocBuilder<NavBloc, NavState> is under your MultiProvider/Provider<NavBloc>.
This usually happens when you are creating a provider and trying to read it immediately.
For example, instead of:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// Will throw a ProviderNotFoundError, because `context` is associated
// to the widget that is the parent of `Provider<Example>`
child: Text(context.watch<Example>()),
),
}
```
consider using `builder` like so:
```
Widget build(BuildContext context) {
return Provider<Example>(
create: (_) => Example(),
// we use `builder` to obtain a new `BuildContext` that has access to the provider
builder: (context) {
// No longer throws
return Text(context.watch<Example>()),
}
),
}
```
If none of these solutions work, consider asking for help on Whosebug:
https://whosebug.com/questions/tagged/flutter
The relevant error-causing widget was:
HomeNav file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12
When the exception was thrown, this was the stack:
#0 Provider._inheritedElementOf (package:provider/src/provider.dart:332:7)
#1 Provider.of (package:provider/src/provider.dart:284:30)
#2 ReadContext.read (package:provider/src/provider.dart:610:21)
#3 _BlocBuilderBaseState.initState (package:flutter_bloc/src/bloc_builder.dart:130:36)
#4 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:4711:57)
...
====================================================================================================
哪里出了问题，我应该怎么做才能解决？
您是否在您正在使用的小部件上方初始化了您的 NavBloc。
如果没有那么也许你可以像这样初始化它：
Scaffold(
body: BlocProvider(
create: (context) => NavBloc(),
child: ...(), // Your class goes here
),
)
只需在您的 HomeNav class 中创建一个 class NavBloc 的实例，并将其传递给 blocbuilder 的 bloc 参数。
解决方案：
class HomeNav extends HookWidget{
@override
Widget build(BuildContext context) {
final navBloc = NavBloc(); // creating an instance of the bloc class
return BlocBuilder<NavBloc, NavState>(
bloc: navBloc, // passing it here
buildWhen: (previous, current) => previous.username != current.username,
builder: (context, state) {
return Scaffold(
body: HomeList(),
bottomNavigationBar: BottomNavigationBar(
items:[
BottomNavigationBarItem(icon: Icon(Icons.home), label: '作品库'),
BottomNavigationBarItem(icon: Icon(Icons.school), label: '我的')
],
currentIndex:state.selectNavIndex
),
);
},
);
}
}