Not able to get the data from the JSON to fields in flutter

Question

I am able to fetch the JSON data from the server in the flutter application. I need to display the data in PageView.builder and nested ListView.builder, this model I have already created.

The code called for implementation

orderdetail = NewOrder.fromJson(json.decode(response.body));

This is the JSON data which I am able to fetch from the server in flutter application

{
    "error": "false",
    "content": [
        {
            "comp_code": "4",
            "comp_name": "KMT OVERSEAS",
            "order_no": "16",
            "order_items": [
                {
                    "comp_code": "4",
                    "comp_name": "KMT OVERSEAS",
                    "order_no": "16",
                },
                {
                    "comp_code": "4",
                    "comp_name": "KMT OVERSEAS",
                    "order_no": "16",
                }
            ]
        },
        {
            "comp_code": "4",
            "comp_name": "KMT OVERSEAS",
            "order_no": "18",
            "order_items": [
                {
                    "comp_code": "4",
                    "comp_name": "KMT OVERSEAS",
                    "order_no": "18",
                },
                {
                    "comp_code": "4",
                    "comp_name": "KMT OVERSEAS",
                    "order_no": "18",

                },
                {
                    "comp_code": "4",
                    "comp_name": "KMT OVERSEAS",
                    "order_no": "18",
                },
               
            ]
        }
    ]
}

The code I used for it is this for fetching the data in the Stateful Widget

  Future<Payload> getdetailsoforders(String userid, String companycode) async {

    SharedPreferences sharedPreferences = await SharedPreferences.getInstance();
    Map data = {
      'user_id': userid,
      'company_code':companycode

    };

    var response = await http.post(newapi, body: data);
    if(response.statusCode == 200) {
     jsonResponse = json.decode(response.body);
      print("jsonrespnse");
      print(jsonResponse);
 }
    

  } else {
  setState(() {
    _isLoading = false;
  });


  print('login error');
  print(response.body);
}

  }

The NewOrder Model class I am implemented is below

import 'newitem.dart';

class NewOrder {
  NewOrder({
    this.sohPk,
    this.orderNo,
    this.newItem,
  });

  String sohPk;
  String orderNo;
 NewItem newItem;

  factory NewOrder.fromJson(Map<String, dynamic> json) => NewOrder(
    sohPk: json["soh_pk"],
    orderNo: json["order_no"],
  newItem:NewItem.fromJson(json['order_items'])
  );

  Map<String, dynamic> toJson() => {
    "soh_pk": sohPk,
    "order_no": orderNo,
   'order_items': newItem.toJson()
  };
}

The NewPlayLoadClass I Implemented is here

import 'package:dataproject2/newmodel/neworder.dart';

class NewPayLoad {
  String error;
  List<NewOrder> content;

  NewPayLoad({this.error, this.content});

  NewPayLoad.fromJson(Map<String, dynamic> json) {
    error = json['error'];
    if (json['content'] != null) {
      content = new List<NewOrder>();
      json['content'].forEach((v) {
        content.add(new NewOrder.fromJson(v));
      });
    }
  }

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

The error I am getting is here

The following NoSuchMethodError was thrown building PageViewClass(dirty, state: _PageViewClassState#98a84): The getter 'content' was called on null. Receiver: null Tried calling: content

I am not able to understand what is wrong with my code, and how to resolve it Please guide further

Answer 1

Use below code

class NewOrder {
  String _error;
  List<Content> _content;

  NewOrder({String error, List<Content> content}) {
    this._error = error;
    this._content = content;
  }

  String get error => _error;
  set error(String error) => _error = error;
  List<Content> get content => _content;
  set content(List<Content> content) => _content = content;

  NewOrder.fromJson(Map<String, dynamic> json) {
    _error = json['error'];
    if (json['content'] != null) {
      _content = new List<Content>();
      json['content'].forEach((v) {
        _content.add(new Content.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['error'] = this._error;
    if (this._content != null) {
      data['content'] = this._content.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Content {
  String _compCode;
  String _compName;
  String _orderNo;
  List<OrderItems> _orderItems;

  Content(
      {String compCode,
      String compName,
      String orderNo,
      List<OrderItems> orderItems}) {
    this._compCode = compCode;
    this._compName = compName;
    this._orderNo = orderNo;
    this._orderItems = orderItems;
  }

  String get compCode => _compCode;
  set compCode(String compCode) => _compCode = compCode;
  String get compName => _compName;
  set compName(String compName) => _compName = compName;
  String get orderNo => _orderNo;
  set orderNo(String orderNo) => _orderNo = orderNo;
  List<OrderItems> get orderItems => _orderItems;
  set orderItems(List<OrderItems> orderItems) => _orderItems = orderItems;

  Content.fromJson(Map<String, dynamic> json) {
    _compCode = json['comp_code'];
    _compName = json['comp_name'];
    _orderNo = json['order_no'];
    if (json['order_items'] != null) {
      _orderItems = new List<OrderItems>();
      json['order_items'].forEach((v) {
        _orderItems.add(new OrderItems.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['comp_code'] = this._compCode;
    data['comp_name'] = this._compName;
    data['order_no'] = this._orderNo;
    if (this._orderItems != null) {
      data['order_items'] = this._orderItems.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class OrderItems {
  String _compCode;
  String _compName;
  String _orderNo;

  OrderItems({String compCode, String compName, String orderNo}) {
    this._compCode = compCode;
    this._compName = compName;
    this._orderNo = orderNo;
  }

  String get compCode => _compCode;
  set compCode(String compCode) => _compCode = compCode;
  String get compName => _compName;
  set compName(String compName) => _compName = compName;
  String get orderNo => _orderNo;
  set orderNo(String orderNo) => _orderNo = orderNo;

  OrderItems.fromJson(Map<String, dynamic> json) {
    _compCode = json['comp_code'];
    _compName = json['comp_name'];
    _orderNo = json['order_no'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['comp_code'] = this._compCode;
    data['comp_name'] = this._compName;
    data['order_no'] = this._orderNo;
    return data;
  }
}