如何在没有上下文的情况下使用提供者？

Question

I have a widget where I use the provider but where I want to use the values is in normal widgets so maybe anyone can help.

This is where I use the provider:

  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});

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======== 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

I'm assuming that your _buildName() is a method of your widget and that you call it from you build method somewhere.

This means that you can pass either the context or the user into this method: _buildName(BuildContext context) {} or _buildName(User user) {}

Try providing more of the code next time, specifically the parts where you call the method.

Edit after post update:

You need to have the user object in the buildName method so you cannot simply do UserData.fullname because UserData is a class not an instance.

So to get your data in the buildName you need to change it to:

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

And call is like: _buildName(userData)