Flutter 错误：找不到正确的提供程序<；NavBloc>；在这个BlocBuilder之上<；NavBloc，NavState>；小装置

现在，我使用flutter状态管理器定义bloc状态管理文件。当我像这样使用集团时：

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
          ),
        );
      },
    );
  }
}

 Scaffold(
  body: BlocProvider(
      create: (context) => NavBloc(),
      child: ...(), // Your class goes here
    ),
  )

import'包：acientbay/src/bloc/nav/nav_bloc.dart'；
导入“package:acientbay/src/page/home/home_list.dart”；
进口“包装：颤振/cupertino.dart”；
进口“包装：颤振/材料.省道”；
进口“包装：颤振团/颤振团.飞镖”；
进口“包装：颤振钩/颤振钩.省道”；
类HomeNav扩展了HookWidget{
@凌驾
小部件构建（构建上下文）{
返回BlocBuilder(
buildWhen：（previous，current）=>previous.username！=current.username，
生成器：（上下文、状态）{
返回脚手架(
正文：HomeList（），
底部导航栏：底部导航栏(
项目：[
BottomNavigationBarItem（图标：图标（Icons.home）），标签：'作品库'),
BottomNavigationBarItem（图标：图标（Icons.school）），标签：'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 StackOverflow:
https://stackoverflow.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 StackOverflow:
https://stackoverflow.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)
...
====================================================================================================

正在执行热重启。。。 正在将文件同步到设备sdk gphone x86 arm。。。 在952ms内重新启动应用程序。 =======小部件库捕获的异常======================================================= 在生成HomeNav时引发了以下ProviderNotFoundException： 错误：在此BlocBuilder小部件上方找不到正确的提供程序 发生这种情况是因为您使用了不包含提供程序的“BuildContext” 由您选择。有几种常见情况： -您在“main.dart”中添加了一个新的提供程序，并执行了热重新加载。 要修复此问题，请执行热重启。 -您试图读取的提供程序位于不同的路径中。 提供者是“范围化”的。因此，如果在路由中插入提供者，则 其他路由将无法访问该提供商。 -您使用了“BuildContext”，它是您试图读取的提供程序的祖先。 确保BlocBuilder在您的MultiProvider/Provider下。 这通常发生在创建提供者并尝试立即读取它时。 例如，而不是： ``` 小部件构建（构建上下文）{ 返回提供者( 创建：（）=>Example（）， //将抛出ProviderNotFoundError，因为'context'已关联 //指向作为“提供者”父级的小部件` 子：文本（context.watch（））， ), } ``` 考虑使用“Builder”这样： ``` 小部件构建（构建上下文）{ 返回提供者( 创建：（）=>Example（）， //我们使用“builder”来获取一个新的“BuildContext”，它可以访问提供者 生成器：（上下文）{ //不再投掷 返回文本（context.watch（））， } ), } ``` 如果这些解决方案都不起作用，请考虑在StAcExpLoad上寻求帮助： https://stackoverflow.com/questions/tagged/flutter 导致错误的相关小部件是： 家庭导航file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12 引发异常时，这是堆栈： #0提供程序。\u继承了elementof（包：Provider/src/Provider.dart:332:7） #1 Provider.of（包：Provider/src/Provider.dart:284:30） #2 ReadContext.read（包：provider/src/provider.dart:610:21） #3\u BlocBuilderBaseState.initState（包：flatter\u bloc/src/bloc\u builder.dart:130:36） #4 StatefulElement.\u firstBuild（包：flatter/src/widgets/framework.dart:4711:57） ... ==================================================================================================== =======小部件库捕获的异常======================================================= 在生成HomeNav时引发了以下ProviderNotFoundException： 错误：在此BlocBuilder小部件上方找不到正确的提供程序 发生这种情况是因为您使用了不包含提供程序的“BuildContext” 由您选择。有几种常见情况： -您在“main.dart”中添加了一个新的提供程序，并执行了热重新加载。 要修复此问题，请执行热重启。 -您试图读取的提供程序位于不同的路径中。 提供者是“范围化”的。因此，如果在路由中插入提供者，则 其他路由将无法访问该提供商。 -您使用了“BuildContext”，它是您试图读取的提供程序的祖先。 确保BlocBuilder在您的MultiProvider/Provider下。 这通常发生在创建提供者并尝试立即读取它时。 例如，而不是： ``` 小部件构建（构建上下文）{ 返回提供者( 创建：（）=>Example（）， //将抛出ProviderNotFoundError，因为'context'已关联 //指向作为“提供者”父级的小部件` 子：文本（context.watch（））， ), } ``` 考虑使用“Builder”这样： ``` 小部件构建（构建上下文）{ 返回提供者( 创建：（）=>Example（）， //我们使用“builder”来获取一个新的“BuildContext”，它可以访问提供者 生成器：（上下文）{ //不再投掷 返回文本（context.watch（））， } ), } ``` 如果这些解决方案都不起作用，请考虑在StAcExpLoad上寻求帮助： https://stackoverflow.com/questions/tagged/flutter 导致错误的相关小部件是： 家庭导航file:///home/dolphin/Documents/GitHub/acientbay/lib/src/app/acientbay_app.dart:12:12 引发异常时，这是堆栈： #0提供程序。\u继承了elementof（包：Provider/src/Provider.dart:332:7） #1 Provider.of（包：Provider/src/Provider.dart:284:30） #2 ReadContext.read（包：provider/src/provider.dart:610:21） #3\u BlocBuilderBaseState.initState（包：flatter\u bloc/src/bloc\u builder.dart:130:36） #4 StatefulElement.\u firstBuild（包：flatter/src/widgets/framework.dart:4711:57） ... =======