从颤动的列表中获取数据

Question

我在实体用户中有一个组织列表，我想做的是读取列表的字段（json 类型）并将其显示在 Futurebuilder 中尝试过这是组织 DTO：

import 'dart:convert';
Organizations organizations(String str) =>
    Organizations.fromJson(json.decode(str));

String OrganizationsToJson(Organizations data) => json.encode(data.tojson());
class Organizations{
  // ignore: non_constant_identifier_names
   Organizations({this.organizationId, this.role, this.createdAt, this.assignmentId});
  // ignore: non_constant_identifier_names
   String organizationId;
   String role;
   String createdAt;
   String   assignmentId;

  factory Organizations.fromJson(Map<String, dynamic> json){

    return Organizations(organizationId: json['organizationId'] , role: json["role"] , createdAt: json["createdAt"] , assignmentId: json["assignmentId"]);

  }




Map<String, dynamic> tojson()=>{
  "organizationId": organizationId,
  "role" : role,
  "createdAt" : createdAt,
  "assignmentId" : assignmentId,

};

  //String get organizationId => organizationId;
  //String get role => role;
  //DateTime get createdAt => createdAt ;
  //String get assignmentId => assignmentId;

  String get organizationID {
    return organizationId;
  }
  String get userRole => role;
  String get creationDate => createdAt;

  String get assignmentid => assignmentId;


}

用户 DTO：

import 'package:helium_app/models/organizations.dart';
import 'dart:convert';
User user(String str) =>
    User.fromJson(json.decode(str));

String UserToJson(User data) => json.encode(data.tojson());

class User{
  // ignore: non_constant_identifier_names
   User({this.email, this.firstname, this.id, this.lastname, this.organizations});


 String email;
 String firstname;
 String id;
 String lastname;
// ignore: non_constant_identifier_names
//final DateTime creation_date;
// ignore: non_constant_identifier_names
//final DateTime last_updated_date;
// ignore: non_constant_identifier_names
//final DateTime last_login_date;
 List<Organizations> organizations;


  factory User.fromJson(Map<String, dynamic> json){
    return User(
        email: json['email'],
        firstname: json['firstname'],
        id: json['id'],
        lastname: json['lastname'],
        //creation_date: json['creation-date'],
       // last_updated_date: json['last-updated-date'],
       // last_login_date: json['last-login-date'],
        organizations: (json['organizations'] as List).
                 map((p) => Organizations.fromJson(p)).toList()



    );
  }


  Map<String, dynamic> tojson()=>{
    "email": email,
    "firstname" : firstname,
    "lastname" : lastname,
    "organizations" : organizations,

  };

  String get userEmail => email;
  String get userFirstName => firstname;
  String get userLastName => lastname;
  List<Organizations> get userOrganizations => organizations;



  }

这是用于解析数据的函数：

Future<User> fetchUser() async {
 final response = await http.get('http://10.0.2.2:8093/user/v1/users/cc535e96-d6ec-4334-9588-890f12122254');

 if (response.statusCode == 200) {
   // If the server did return a 200 OK response,
   // then parse the JSON.
   return User.fromJson(jsonDecode(response.body));
 } else {
   // If the server did not return a 200 OK response,
   // then throw an exception.
   throw Exception('Failed to load user');
 }
}

我尝试了这种方法从列表中获取我想要的字段（角色和创建日期）：

Future<User> futureUser;

  get index => null;
  ListTile(
  contentPadding: EdgeInsets.all(0),
  title: Text("organisation"),
  subtitle: Text(snapshot.data.organizations[index].role)
      )],

在futurebuilder ofc和widget build方法中， 但我只得到这个错误：

enter image description here

这是整个例子：

class Profile extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _ProfileHomeState();
  }
}

Future<User> fetchUser() async {
  final response = await http.get('http://10.0.2.2:8093/user/v1/users/cc535e96-d6ec-4334-9588-890f12122254');

  if (response.statusCode == 200) {
    // If the server did return a 200 OK response,
    // then parse the JSON.
    return User.fromJson(jsonDecode(response.body));
  } else {
    // If the server did not return a 200 OK response,
    // then throw an exception.
    throw Exception('Failed to load user');
  }
}



class _ProfileHomeState extends State<Profile> {
  Future<User> futureUser;

  get index => null;


  
  


  @override
  void initState() {
    super.initState();
    futureUser = fetchUser();
  }

   //getUserInformation() async{


    //var response = await http.get('http://localhost:8093/user/v1/users/2e48ff17-b327-4db6-a60b-97a9fcc20362');



      //var jsonData = json.decode(response.body);
      //firstname = jsonData['firstname'];
     // lastname = jsonData['lastname'];
      //email = jsonData['email'];


      //setState(() {

        //var jsonData = json.decode(response.body);
        //firstname = jsonData['firstname'];
        //lastname = jsonData['lastname'];
        //email = jsonData['email'];


      //});
     // print (firstname);
      //print (lastname);
     // print (email);

// }







  //static final String path = "lib/screens/profile/profile_home.dart";
  final image = 'assets/images/user_profile.png';
  @override
  Widget build(BuildContext context){
   return Scaffold(
       body: SingleChildScrollView(
         child : FutureBuilder<User>(

           future: futureUser,
           // ignore: missing_return
           builder:(context, snapshot){
             if (snapshot.hasData) {
               return Stack(
              children: [
                SizedBox(
                  height: 250,
                  width: double.infinity,
                  //child: Image.asset(image, fit: BoxFit.cover,),
                  child: Container(
                    height: 360,
                    decoration: BoxDecoration(
                        borderRadius: BorderRadius.only(bottomLeft: Radius.circular(50.0), bottomRight: Radius.circular(50.0)),
                        gradient: LinearGradient(
                            colors: [kPrimaryColor,color2],
                            begin: Alignment.topLeft,
                            end: Alignment.bottomRight
                        )
                    ),
                  ),
                ),
                Container(
                  margin: EdgeInsets.fromLTRB(16.0, 200.0, 16.0, 16.0),
                  child: Column(
                    children: <Widget>[
                      Stack(
                        children: <Widget>[
                          Container(
                            padding: EdgeInsets.all(16.0),
                            margin: EdgeInsets.only(top: 16.0),
                            decoration: BoxDecoration(
                                color: Colors.white,
                                borderRadius: BorderRadius.circular(5.0)
                            ),
                            child: Column(
                              crossAxisAlignment: CrossAxisAlignment.start,
                              children: <Widget>[
                                Container(
                                  margin: EdgeInsets.only(left: 96.0),
                                  child: Column(
                                    crossAxisAlignment: CrossAxisAlignment.start,
                                    children: <Widget>[
                                      Text(snapshot.data.firstname, style: Theme.of(context).textTheme.title,),
                                      ListTile(
                                        contentPadding: EdgeInsets.all(0),
                                        title: Text("organisation"),
                                        subtitle: Text(snapshot.data.organizations[index].role)
                                      )],
                                  ),
                                ),
                                SizedBox(height: 10.0),

                              ],
                            ),
                          ),
                          Container(
                            height: 80,
                            width: 80,
                            decoration: BoxDecoration(
                                borderRadius: BorderRadius.circular(10.0),
                                image: DecorationImage(
                                    image: AssetImage(image),
                                    fit: BoxFit.cover
                                )
                            ),
                            margin: EdgeInsets.only(left: 16.0),
                          ),
                        ],
                      ),

                      SizedBox(height: 20.0),
                      Container(
                        decoration: BoxDecoration(
                          color: Colors.white,
                          borderRadius: BorderRadius.circular(5.0),
                        ),
                        child: Column(
                          children: <Widget>[
                            ListTile(title: Text("User information"),),
                            Divider(),
                            ListTile(
                              title: Text("Email"),
                              subtitle: Text(snapshot.data.email),
                              leading: Icon(Icons.email,color: kPrimaryColor),
                            ),

                            ListTile(
                              title: Text("Organisation"),
                              subtitle: Text("https://www.littlebutterfly.com"),
                              leading: Icon(Icons.people,color: kPrimaryColor),
                            ),

                            ListTile(
                              title: Text("Joined Date"),
                              subtitle: Text(snapshot.data.organizations[index].createdAt),
                              leading: Icon(Icons.calendar_view_day,color: kPrimaryColor,),
                            ),
                          ],
                        ),
                      )
                    ],
                  ),
                ),
                AppBar(
                  backgroundColor: Colors.transparent,
                  elevation: 0,
                )
              ],
               );

             }
             else if (snapshot.hasError) {
               return Text("${snapshot.error}");
             }

             return CircularProgressIndicator();



           }


         ),





       ),





   );



     }




}

如果有人能帮忙解决这个问题或知道哪里出了问题，我将不胜感激

Answer 1

organization_model.dart

class OrganizationModel {
  String _id, _role, _createdAt, _assignmentId;

  OrganizationModel.fromJson(Map<String, dynamic> data) {
    _id = data['organizationId'];
    _role = data['role'];
    _createdAt = data['createdAt'];
    _assignmentId = data['assignmentId'];
  }

  String get id => _id;
  String get userRole => _role;
  String get creationDate => _createdAt;
  String get assignmentId => _assignmentId;

  String show() => '''
    ID : $_id
    Role : $_role
    Created At : $_createdAt
    Assignment ID : $_assignmentId

''';
}

user_model.dart

import 'package:read_json/models/organization_model.dart';


class UserModel {
  String _id, _firstName, _lastName, _email;
  var _organizations =  List<OrganizationModel>();

  UserModel.fromJson(Map<String, dynamic> data) {
    _id = data['id'];
    _firstName = data['firstname'];
    _lastName = data['lastname'];
    _email = data['email'];
    (data['organizations'] as List).forEach((e) => _organizations.add(OrganizationModel.fromJson(e)));
  }

  String get id  => _id;
  String get firstName  => _firstName;
  String get lastName  => _lastName;
  String get email  => _email;
  List<OrganizationModel> get organizations  => _organizations;

  String show() => '''
ID : $_id
First Name : $_firstName
Last Name : $_lastName
eMail : $_email

Organizations :

${_organizations.fold("", (s, e) => s + e.show())}
''';
}

net_service.dart

import 'dart:convert';

import 'package:http/http.dart' as http;
import 'package:read_json/models/user_model.dart';


const userData = '''
{
  "data": {
    "id": "5",
    "firstname": "Billiardo",
    "lastname": "Aragorn",
    "email": "nobody@arcadia.net",
    "organizations": [
      {
        "organizationId": "002",
        "role": "noob",
        "createdAt" : "1234343535",
        "assignmentId" : "2346757"
      },
      {
        "organizationId": "003",
        "role": "pro",
        "createdAt" : "234324354352",
        "assignmentId" : "3245546435"
      }
    ]
  }
}
''';

class NetService {
  static Future fetchJsonData(String url) {
    return
      http.get(url)
        .then((response) => response?.statusCode == 200 ? jsonDecode(response.body) : null)
        .catchError((err) => print(err));
  }

  static Future<UserModel> fetchUser() {
    return fetchJsonData('http://10.0.2.2:8093/user/v1/users/cc535e96-d6ec-4334-9588-890f12122254')
      .then((response) => (response != null) ? UserModel.fromJson(response['data']) : null)
      .catchError((err) => print('OMFG!!! an error: $err'));
  }

  static Future<UserModel> fetchLocalUser() {
    return Future<UserModel>.delayed(
      Duration(seconds: 3),
      () => UserModel.fromJson(jsonDecode(userData)['data']),
    );
  }
}

home_page.dart

import 'package:flutter/material.dart';
import 'package:read_json/models/user_model.dart';
import 'package:read_json/services/net_service.dart';


class HomePage extends StatelessWidget {
  /* ---------------------------------------------------------------------------- */
  const HomePage({Key key}) : super(key: key);
  /* ---------------------------------------------------------------------------- */
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Hi!'),
        centerTitle: true,
      ),
      body: FutureBuilder<UserModel>(
        future: NetService.fetchLocalUser(),
        builder: (context, snapshot) => snapshot.hasData
            ? Text(snapshot.data.show())
            : snapshot.hasError
              ? Text('Something was wrong!: ${snapshot.error}')
              : Text('Loading...'),
      ),
    );
  }
}