错误：在此UpdateSupervisor小部件

如何解决错误：在此UpdateSupervisor小部件

如何在onpressed 函数中包装流提供程序？这是我的课程。

UpdateSupervisor类

import 'package:finalyearproject/model/NewUser.dart';
import 'package:finalyearproject/service/database.dart';
import 'package:finalyearproject/shared/Loading.dart';
import 'package:Flutter/cupertino.dart';
import 'package:Flutter/material.dart';
import 'package:provider/provider.dart';



class UpdateSupervisor extends StatefulWidget {


  @override
  _UpdateSupervisorState createState() => _UpdateSupervisorState();
}

class _UpdateSupervisorState extends State<UpdateSupervisor> {

  // form values
   String name;
   String email;
   String uniqueID;
   String phone;
   String id;
   
  final GlobalKey<FormState> _formKey = GlobalKey();

  @override
  Widget build(BuildContext context) {
    final user = Provider.of<NewUser>(context);
    return Scaffold(
      appBar: AppBar(
        title: Text('Edit Supervisor'),backgroundColor: Colors.redAccent,),body: StreamBuilder(
        stream: DatabaseService(uid: user.id).userData,builder: (context,snapshot){
          if(!snapshot.hasData){
            return Loading();
          }
          NewUser userData = snapshot.data;
          return Form(
            key: _formKey,child: SingleChildScrollView(
              padding: const EdgeInsets.all(16.0),child: Column(
                crossAxisAlignment: CrossAxisAlignment.end,children: <Widget>[
                  SizedBox(height: 25.0),TextFormField(
                    decoration: Inputdecoration(
                        hintText: 'Name',border: OutlineInputBorder(borderRadius: BorderRadius.circular(5))),keyboardType: TextInputType.text,initialValue: userData.name,validator: (value) => value.isEmpty ? 'Name cannot be empty!': null,onChanged: (value) {
                      setState(() => name = value);
                    },SizedBox(height: 10.0),TextFormField(
                    decoration: Inputdecoration(
                        hintText: 'Email',keyboardType: TextInputType.emailAddress,validator: (value) => value.isEmpty ? 'Email cannot be empty!': null,onChanged: (value) {
                      setState(() => email = value);
                    },TextFormField(
                    decoration: Inputdecoration(
                        hintText: 'Number Phone',keyboardType: TextInputType.number,validator: (value) => value.isEmpty ? 'Number Phone cannot be empty!': null,onChanged: (value) {
                      setState(() => phone = value);
                    },TextFormField(
                    decoration: Inputdecoration(
                        hintText: 'Unique ID ',validator: (value) => value.isEmpty ? 'Ic number cannot be empty!': null,onChanged: (value) {
                      setState(() => uniqueID = value);
                    },const SizedBox(height: 20.0),RaisedButton(
                      color: Colors.redAccent,textColor: Colors.black,child: Text("Update"),onpressed: () async {
                        if(_formKey.currentState.validate()){

                          _formKey.currentState.save();
                        } else {
                          print("Validator are correct!");
                        }
                      }
                  ),],);
        }
      )
    );

  }
}

HomeSupervisor类

import 'package:Flutter/material.dart';
import 'package:finalyearproject/model/NewUser.dart';
import 'package:finalyearproject/screen/crud/UpdateSupervisor.dart';
import 'package:finalyearproject/screen/crud/AddSupervisor.dart';
import 'package:finalyearproject/service/database.dart';
import 'package:finalyearproject/sidebar/AdminDrawer.dart';


class HomeSupervisor extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.redAccent,title: Text('Supervisor'),actions: <Widget>[
          IconButton(
              icon: Icon(
                Icons.add,color: Colors.white,onpressed: () {
                Navigator.push(context,MaterialPageRoute(builder: (context) => AddSupervisor()));
              })
        ],drawer: AdminDrawer(),body: ListSupervisor(),);
  }

}

class ListSupervisor extends StatefulWidget {
  @override
  _ListSupervisorState createState() => _ListSupervisorState();
}

class _ListSupervisorState extends State<ListSupervisor> {
  NewUser user;

  @override
  Widget build(BuildContext context) {
    return Container(
      child: FutureBuilder(
          future: DatabaseService().getPost(),builder: (_,snapshot) {
            if (snapshot.connectionState == ConnectionState.waiting) {
              return Center(
                child: Text("Loading..."),);
            } else {
              return ListView.builder(
                  itemCount: snapshot.data.length,itemBuilder: (_,index) {
                    return Card(
                      child: ListTile(
                          title: Container(
                            alignment: Alignment.centerLeft,child: Column(
                              children: <Widget>[
                                SizedBox(height: 5.0),Container(alignment: Alignment.centerLeft,child: Text(
                                      snapshot.data[index].data["name"]),SizedBox(height: 5.0),child: Text(
                                      snapshot.data[index].data["email"]),child: Text(
                                      snapshot.data[index].data["uniqueID"]),trailing: Row(
                            mainAxisSize: MainAxisSize.min,children: <Widget>[
                              IconButton(
                                  icon: Icon(Icons.delete),color: Colors.red,onpressed: (){

                                  }
                              ),IconButton(
                                  icon: Icon(Icons.edit),color: Colors.black,onpressed: () {
                                    Navigator.push(context,MaterialPageRoute(builder: (context) => UpdateSupervisor()));  //here the line error show//
                                  }
                              ),IconButton(
                                  icon: Icon(Icons.share),onpressed: () {

                                  }
                              ),)
                      ),);
                  });
            }
          }),);
  }
}

然后erorr显示，在96：101行中，我将nagivator.push的Iconbutton推送到UpdateSupervisor。所以我的问题是如何在onpressed（）中包装流提供程序？

错误：在此UpdateSupervisor小部件上方找不到正确的提供程序

要解决，请：

确保提供者是此UpdateSupervisor小部件的祖先
向提供者提供类型
为消费者提供类型
将类型提供给Provider.of（）
始终使用包导入。例如：`import'package：my_app / my_code.dart';
确保使用正确的context。

如果这些解决方案均无效，请在以下位置提交错误： https://github.com/rrousselGit/provider/issues 相关的引起错误的小部件是： UpdateSupervisor文件：/// D：/Android_project/finalyearproject/lib/screen/home/HomeSupervisor.dart：96：101

解决方法

使用这样的提供程序包装MaterialApp。

ChangeNotifierProvider<NewUser>(create: (context) => NewUser(),child: MaterialApp(
        title: 'Flutter Demo',home:Home(),),);

另外：我正在使用 ChangeNotifierProvider ，因为我假设您的提供商正在扩展 ChangeNotifier 。

如果您不扩展 ChangeNotifier ，则可以使用以下提供程序的基本形式：

Provider<NewUser>(
  create: (context) => NewUser(),child: child: MaterialApp(
        title: 'Flutter Demo',)

这将使您可以将 NewUser 对象用作对所有Provider后代类的依赖项注入，如下所示：

class HomeWidget extends StatelessWidget {
  @override
  Widget buid(BuildContext context){
    final provider = Provider.of<NewUser>(contextm,listen:false); /// you can to not set listen on false it does not matter in this case cause this type of provider is just an injection
    return Text(provider.someText);

   }
}

还有 StreamProvider ，您可以在流中收听并更新 Widget ，当出现此问题时，该注入该提供程序流将接收数据，也将其检出。

还有一个 MultiProvider ，可让您将MaterialApp与多个提供程序包装在一起。

还要检查此url

来自flutter.dev 的 MultiProvider 的

示例

void main() {
  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (context) => CartModel()),Provider(create: (context) => SomeOtherClass()),],child: MyApp(),);
}