如何在没有上下文的情况下使用提供者？

Question

我有一个小部件，我在其中使用提供程序，但我想在普通小部件中使用这些值，所以也许任何人都可以提供帮助。

这是我使用提供程序的地方：

  Widget _buildName(BuildContext context) {
    return Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            Text(
              'Full Name',
              style: kLabelStyle3,
            ),
            SizedBox(height: 10.0),
            Container(
              alignment: Alignment.centerLeft,
              height: 50.0,
              child: TextFormField(
                initialValue: UserData.fullname;
                validator: (val) => val.isEmpty ? 'Enter your Name' : null,
                onChanged: (val) {
                  setState(() => _currentfullname = val);
                },
                style: TextStyle(
                  color: Colors.black,
                  fontFamily: 'OpenSans',
                ),
                decoration: InputDecoration(
                  enabledBorder: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(25.0),
                    borderSide: BorderSide(
                      color: Colors.black,
                      width: 2.0,
                    ),
                  ),
                  contentPadding: EdgeInsets.only(top: 14.0),
                  prefixIcon: Icon(
                    Icons.person,
                    color: Colors.black,
                  ),
                  hintText: 'Enter your Name',
                  hintStyle: kHintTextStyle2,
                ),
              ),
            ),
          ],
        );

  }

  @override
  Widget build(BuildContext context) {
final user = Provider.of<Userr>(context);
        return StreamBuilder<UserData>(
          stream: DatbaseService(uid:user.uid).userData,
          builder: (context, snapshot) {
            if(snapshot.hasData){
              UserData userData =snapshot.data;
              return Scaffold(
                appBar: AppBar(
                  backgroundColor: Colors.transparent,
                  elevation: 0.0,
                ),
                body: AnnotatedRegion<SystemUiOverlayStyle>(
                  value: SystemUiOverlayStyle.light,
                  child: GestureDetector(
                    onTap: () => FocusScope.of(context).unfocus(),
                    child: Form(
                      key: _formKey,
                      child: Stack(
                        children: <Widget>[
                          Container(
                            height: double.infinity,
                            child: SingleChildScrollView(
                              physics: AlwaysScrollableScrollPhysics(),
                              padding: EdgeInsets.symmetric(
                                horizontal: 40.0,
                                vertical: 10,
                              ),
                              child: Column(
                                mainAxisAlignment: MainAxisAlignment.center,
                                children: <Widget>[
                                  Center(
                                    child: Stack(
                                      children: [
                                        Container(
                                          width: 110,
                                          height: 110,
                                          decoration: BoxDecoration(

                                              borderRadius: BorderRadius.circular(100),
                                              image: DecorationImage(
                                                  fit: BoxFit.cover,
                                                  image: NetworkImage(
                                                    "https://images.pexels.com/photos/3307758/pexels-photo-3307758.jpeg?auto=compress&cs=tinysrgb&dpr=3&h=250",
                                                  ))),
                                        ),
                                        Positioned(
                                            bottom: 0,
                                            right: 0,
                                            child: Container(
                                              height: 35,
                                              width: 35,
                                              decoration: BoxDecoration(
                                                shape: BoxShape.circle,
                                                border: Border.all(
                                                  width: 4,
                                                  color: Theme.of(context)
                                                      .scaffoldBackgroundColor,
                                                ),
                                                color: Colors.green,
                                              ),
                                              child: Icon(
                                                Icons.edit,
                                                color: Colors.white,
                                              ),
                                            )),
                                      ],
                                    ),
                                  ),
                                  SizedBox(
                                    height: 10,
                                  ),
                                  Text(
                                    'Mein Profil',
                                    style: TextStyle(
                                      color: Colors.black,
                                      fontFamily: 'OpenSans',
                                      fontSize: 20.0,
                                      fontWeight: FontWeight.w600,
                                    ),
                                  ),
                                  showAlert2(),

                                    _buildEmailTF(),
                                  SizedBox(
                                    height: 30.0,
                                  ),
                                  _buildName(),
                                  SizedBox(
                                    height: 30.0,
                                  ),
                                  _builduserName(),
                                  SizedBox(
                                    height: 30.0,
                                  ),
                                  _buildPasswordTF(),
                                  SizedBox(height: 30,),

                                  _buildPassword2TF(),
                                  _buildUpdateDataButton(),
                                  // _buildEmailform(),
                                ],
                              ),
                            ),
                          )
                        ],
                      ),
                    ),
                  ),
                ),

              );

            }else{
return null;
            }


          }
        );


      }



  }

class DatbaseService{

  final String uid;
  DatbaseService({this.uid});
  //collection reference
  final CollectionReference myprofilsettings = FirebaseFirestore.instance.collection('meinprofilsettings');

  Future updateUserData(String user,String fullname,String password,String email)async{
    return await myprofilsettings.doc(uid).set({
      'username':user,
      'fullname':fullname,
      'passwort':password,
      'email':email,
    });

  }

  //profil list from snapshot
  List<myprofil> _myprofillistFromSnapshot(QuerySnapshot snapshot){
    return snapshot.docs.map((doc){
      return myprofil(
        user: doc.data()['user']??'',
        fullname: doc.data()['fullname']??'',
        email: doc.data()['email']??'',
        passowrd: doc.data()['password']??'',


      );
    }).toList();
  }
  //userData from snapshot
  UserData _userDataFromSnapshot(DocumentSnapshot snapshot){
    return UserData(
      uid: uid,
      name: snapshot.data()['name'],
      fullname: snapshot.data()['fullname'],
      email: snapshot.data()['email'],
      password: snapshot.data()['password'],


    );
  }
  //get myprofilsettings stream
  Stream<List<myprofil>> get settings{
    return myprofilsettings.snapshots().map(_myprofillistFromSnapshot);
  }

  //get user doc stream
Stream<UserData> get userData{
    return myprofilsettings.doc(uid).snapshots().map(_userDataFromSnapshot);
}
}

import 'package:flutter/cupertino.dart';

class Userr{

  final String uid;

  Userr({this.uid});



}
class UserData {
  final String uid;
  final String user;
  final String fullname;
  final String email;
  final String passowrd;

  UserData({this.uid,this.user,this.fullname,this.email,this.passowrd, name, password});

忽略这一点：因为 flutter 说 __it looks like 看起来您的帖子主要是代码； 请添加更多细节。 ___ IM adding some textdehpkfnwrfemrjfikerfoiwnfdoiwjefiojnweoidfjwiodjwiojdoijweiodjweiojdoiewjdijewoijdoejwdiojewiojdiowjedijweoidjiowediwjdoiwejdiowjdiojwoidjaldknjlncjnnc xy,,y,y,,y,ykampkdnndendiowendiojweiopjdipqejkdpojkdposkqwpodkqopwkdopkqwopdskqopdkpoqwkdopqkwopdkqwpodkpoqkdpkqpodkpqkdpokdpo<skcpoaskdpoakdopkdpoekwopdkwepokdpowekdpokwepodkwepokdpowekdpowekpdkpekdpokeopdkpekdpowekdopewkpdkwpekdpwekdpowekdpowekdpowekdpkwepodkwepodkpoekdpoewkdpoekdp

======== Exception caught by widgets library =======================================================
The following assertion was thrown building StreamBuilder<UserData>(dirty, state: _StreamBuilderBaseState<UserData, AsyncSnapshot<UserData>>#c612d):
A build function returned null.

The offending widget is: StreamBuilder<UserData>
Build functions must never return null.

To return an empty space that causes the building widget to fill available room, return "Container()". To return an empty space that takes as little room as possible, return "Container(width: 0.0, height: 0.0)".

The relevant error-causing widget was: 
  StreamBuilder<UserData> file:///Users/name/StudioProjects/project/lib/seitenleiste/meinacount.dart:356:16
When the exception was thrown, this was the stack: 
#0      debugWidgetBuilderValue.<anonymous closure> (package:flutter/src/widgets/debug.dart:305:7)
#1      debugWidgetBuilderValue (package:flutter/src/widgets/debug.dart:326:4)
#2      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4592:7)
#3      StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:4759:11)
#4      Element.rebuild (package:flutter/src/widgets/framework.dart:4281:5)
...
====================================================================================================

Answer 1

我假设您的_buildName()是您的小部件的一种方法，并且您从某处的构建方法中调用它。

这意味着您可以将上下文或用户传递到此方法中： _buildName(BuildContext context) {}或_buildName(User user) {}

下次尝试提供更多代码，特别是调用方法的部分。

发布更新后编辑：

您需要在 buildName 方法中拥有用户 object ，因此您不能简单地执行UserData.fullname因为UserData是 class 而不是实例。

因此，要在 buildName 中获取数据，您需要将其更改为：

_buildName(UserData userData) {
  userData.fullname; // this now exists
}

调用就像： _buildName(userData)