我正在尝试借助颤振中的模型类从 api 加载数据

Question

I am trying to fetch data from api and bind with model class at the time of loading data with list im getting null object. i havae tried so many solutions but no one method will work. the code which i have tried from github.

class _ChooseRecipientPageState extends State<ChooseRecipient1> {

  void recepinets(){
    receipientModel().then((dynamic res){
      setState(() {
        widget._recepientModel=res;
      });
    });
  }

  //Here i am trying to access data from model class which is load in list type of variable

          Container(
            child: new Flexible(
              child: ListView.builder(
                itemCount:widget._recepientModel.length,
                itemBuilder: (context,index) {
                  return GestureDetector(
                    onTap: () => {
                      Navigator.push(
                        context,
                        MaterialPageRoute(
                          builder: (context) => PostYourStatus(
                          ),
                        ),
                      ),
                    },

//Here i am trying to access data from model class which is load in list type of variable and with the help of this variable i will access its property.

                          Container(
                            width: 230,
                            child: Padding(
                              padding: const EdgeInsets.all(10),
                              child: Column(
                                children: <Widget>[
                                  Row(
                                    children: <Widget>[
                                      Text(
                                        '${widget._recepientModel[index].successData[index].firstName}',
                                        style: TextStyle(
                                            fontFamily: 'Poppins',
                                            fontSize: 17),
                                      ),
                                    ],
                                  ),

// Here its my model class

import 'package:http/http.dart' as http;
import 'dart:convert';
import 'package:shared_preferences/shared_preferences.dart';


class RecepientModel {
  String status;
  List<SuccessData> successData;
  int dataCount;

  RecepientModel({this.status, this.successData, this.dataCount});

  RecepientModel.fromJson(Map<String, dynamic> json) {
    status = json['status'];
    if (json['success_data'] != null) {
      successData = new List<SuccessData>();
      json['success_data'].forEach((v) {
        successData.add(new SuccessData.fromJson(v));
      });
    }
    dataCount = json['data_count'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['status'] = this.status;
    if (this.successData != null) {
      data['success_data'] = this.successData.map((v) => v.toJson()).toList();
    }
    data['data_count'] = this.dataCount;
    return data;
  }
}

class SuccessData {
  int id;
  String firstName;
  String lastName;
  String email;
  String phoneNumber;
  String profileImage;
  String giftedTagLine;

  SuccessData(
      {this.id,
        this.firstName,
        this.lastName,
        this.email,
        this.phoneNumber,
        this.profileImage,
        this.giftedTagLine});

  SuccessData.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    firstName = json['first_name'];
    lastName = json['last_name'];
    email = json['email'];
    phoneNumber = json['phone_number'];
    profileImage = json['profile_image'];
    giftedTagLine = json['gifted_tag_line'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['first_name'] = this.firstName;
    data['last_name'] = this.lastName;
    data['email'] = this.email;
    data['phone_number'] = this.phoneNumber;
    data['profile_image'] = this.profileImage;
    data['gifted_tag_line'] = this.giftedTagLine;
    return data;
  }
}

Future<List<SuccessData>> receipientModel() async {
  SharedPreferences prefs = await SharedPreferences.getInstance();
  var accessToken =prefs.getString("token");
  var id =prefs.getString("id");
  var url = 'https://bruyou.project-demo.info/api/V1/customer/${id}/chooseRecipient';
  //encode Map to JSON
  var response = await http.get(url,headers: {"Content-Type": "application/json","Authorization":accessToken},);
  final responseJson = json.decode(response.body);
  Iterable list=responseJson['successData'];

  if(responseJson['status']==200){
    return list.map((mod) => SuccessData.fromJson(mod)).toList();
  }
}

Answer 1

You are trying to do a setState on StatelessWidget by widget.variable . You didn't show all widget, but I guess it has some property of _recepientModel which is probably null during Widget render. If you want to fetch data on Widget load, you should add _recepientModel state variable in StatefullWidget and inside initState lifecycle function, call api fech and then do a setState wich will rerender the widget with new data.

What's more you should do some kind of assertion that _recepientModel (I'm only guessing is a List) isn't null or has some items inside. If not, then it won't render inside itemBuilder . To make it easy you can set _recepientModel state variable as empty list at the beginning.