Flutter TreeView Json Data Parsing

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I want to use this flutter treeview widget in my flutter app to build companies treeview
https://pub.dev/packages/tree_view
i have a webservice with list of companies in a tree structure. https://washservice.com/api/companyXML/1fe5bae2-331a-4080-b34f-5ebd3518efd8
I have written json parsing code with recursive function to build treeview but it is not working .can someone help me to fix parsing issue and build treeview widget
Here is my code
import 'dart:async';
import 'dart:convert';
import 'package:example/models/Company.dart';
import 'package:example/widgets/directory_widget.dart';
import 'package:example/widgets/file_widget.dart';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'package:tree_view/tree_view.dart';
class CompaniesPage extends StatefulWidget {
  CompaniesPage({Key key, this.title}) : super(key: key);
  final String title;
  @override
  _CompaniesPageState createState() => _CompaniesPageState();
class _CompaniesPageState extends State<CompaniesPage> {
  List<Company> companiesList = new List<Company>();
  @override
  void initState() {
    super.initState();
    // Loading initial data or first request to get the data
    _getTeeViewData1();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title ?? 'Tree View demo'),
      body: Center(
        child: TreeView(
          startExpanded: false,
          children: _getChildList(companiesList),
  // Webservice request to load 20 users data using paging
  Future<List<Company>> _getTeeViewData1() async {
    String url =      
        "https://washservice.com/api/companyXML/1fe5bae2-331a-4080-b34f-5ebd3518efd8";
    print(url);
    var response = await http.get(url);
    var jsonData = json.decode(response.body);
    print(jsonData);
    var data = jsonData["Companies"];
    var companies = data["Company"];
    print(companies);
    Company c = new Company();
    c.CompanyId = companies["CompanyId"];
    c.CompanyName = companies["CompanyName"];
    c.ParentId = companies["ParentId"];
    c.CostCenter = '${companies["CostCenter"] ?? ""}';
    c.IsSelectableforMovement = companies["IsSelectableforMovement"];
    c = getChildCompanies(companies["Company"], c);
    companiesList.add(c);
    return companiesList;
  Company getChildCompanies(childCompanies, parentCompany) {
    if (childCompanies != null) {
      for (var childCompany in childCompanies) {
        Company childCO = new Company();
        childCO.CompanyId = childCompany["CompanyId"];
        childCO.CompanyName = childCompany["CompanyName"];
        childCO.ParentId = childCompany["ParentId"];
        childCO.CostCenter = '${childCompany["CostCenter"] ?? ""}';
        childCO.IsSelectableforMovement =
            childCompany["IsSelectableforMovement"];
        Company c2 = getChildCompanies(childCompany["Company"], childCO);
        parentCompany.company.add(c2);
        return parentCompany;
  List<Widget> _getChildList(List<Company> childDocuments) {
    return childDocuments.map((document) {
      if (document.company.length != 0) {
        return Container(
          margin: EdgeInsets.only(left: 8),
          child: TreeViewChild(
            parent: _getDocumentWidget(document: document),
            children: _getChildList(document.company),
      return Container(
        margin: const EdgeInsets.only(left: 4.0),
        child: _getDocumentWidget(document: document),
    }).toList();
  Widget _getDocumentWidget({@required Company document}) =>
      document.company.length == 0
          ? _getFileWidget(document: document)
          : _getDirectoryWidget(document: document);
  DirectoryWidget _getDirectoryWidget({@required Company document}) =>
      DirectoryWidget(directoryName: document.CompanyName);
  FileWidget _getFileWidget({@required Company document}) =>
      FileWidget(fileName: document.CompanyName);
Company.dart
class Company {
   Company();
   String CompanyId;
   String CompanyName;
   String ParentId;
   String CostCenter;
   String IsSelectableforMovement;
   List<Company> company = new List<Company>();
I used the same package with my own json data. Here  you can find a sample of usage. Maybe you can adapt it for your use.
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:tree_view/tree_view.dart';
void main() {
  runApp(MyApp());
class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'title',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      initialRoute: '/',
      routes: {
        '/': (context) => TestPage(),
class TestPage extends StatefulWidget {
  @override
  _TestPageState createState() => _TestPageState();
class _TestPageState extends State<TestPage> {
  String responseBody =
      '{ "id": 0,"name": "A","children": [{  "id": 1, "name": "Aa","children": [{"id": 2,"name": "Aa1","children": null}]},{ "id": 3, "name": "Ab","children": [{"id": 4,"name": "Ab1","children": null},{"id": 5,"name": "Ab2","children": null}]}]}';
  @override
  Widget build(BuildContext context) {
    Map mapBody = jsonDecode(responseBody);
    return SafeArea(
      child: Scaffold(
        body: printGroupTree(
          mapBody,
  Widget printGroupTree(
    Map group, {
    double level = 0,
    if (group['children'] != null) {
      List<Widget> subGroups = List<Widget>();
      for (Map subGroup in group['children']) {
        subGroups.add(
          printGroupTree(
            subGroup,
            level: level + 1,
      return Parent(
        parent: _card(
          group['name'],
          level * 20,
        childList: ChildList(
          children: subGroups,
    } else {
      return _card(
        group['name'],
        level * 20,
  Widget _card(
    String groupName,
    double leftPadding,
    return Container(
      padding: EdgeInsets.only(
        left: leftPadding + 5,
        right: 20,
      decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(50.0),
      height: 100,
      child: Row(
        children: <Widget>[
          Container(
            width: 250,
            child: Row(
              children: <Widget>[
                Container(
                  height: 70,
                  width: 70,
                  decoration: BoxDecoration(
                    shape: BoxShape.rectangle,
                    image: DecorationImage(
                      fit: BoxFit.fill,
                      image: NetworkImage(
                        'https://upload.wikimedia.org/wikipedia/commons/thumb/a/a6/Rubik%27s_cube.svg/220px-Rubik%27s_cube.svg.png',
                SizedBox(
                  width: 10,
                Flexible(
                  child: Text(
                    'SomeText',
          Expanded(
            child: SizedBox(),
          InkWell(
            //TODO:Empty method here
            onTap: () {},
            child: Icon(
              Icons.group_add,
              size: 40,
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