我想在我的flutter应用程序中使用此flutter treeview小部件来构建公司treeview

https://pub.dev/packages/tree_view

我有一个以树状结构列出公司的网络服务。
https://washservice.com/api/companyXML/1fe5bae2-331a-4080-b34f-5ebd3518efd8

我已经编写了具有递归功能的json解析代码以构建treeview，但是它无法正常工作。有人可以帮助我修复解析问题并构建treeview小部件吗？

这是我的代码

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);
}

公司

class Company {
   Company();
   String CompanyId;
   String CompanyName;
   String ParentId;
   String CostCenter;
   String IsSelectableforMovement;
   List<Company> company = new List<Company>();
}