how to display data from json api using flutter expansiontile

import 'dart:async';
import 'package:intl/intl.dart';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
//import 'package:shared_preferences/shared_preferences.dart';
import 'package:http/http.dart' as http;
//import 'package:cswauthapp/models.dart';
import 'package:flutter/foundation.dart';
import 'dart:convert';

var jsonCodec = const JsonCodec();
List<Exp> myReasonList;
List myDCList;
int mycount = 0;

void main() {
  runApp(new MyApp());

}



class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'ExpansionTile Test',
      home: new MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  @override
  void initState() {
    super.initState();

    _getData();
    //_getSpecialty();
  }

  _getData() async {
    var _url = 'http://$baseurl:8080/support/dc/1';

    var http = createHttpClient();
    var response = await http.get(_url);

    var dc = await jsonCodec.decode(response.body);
    myDCList = await dc.toList();



    print('DC: '+myDCList.toString());

    if (mounted) {
      setState(() {
        //_dataReceived = true;
        mycount = myDCList.length;
      });
    }

  }

  Future _getChildren(int did) async {

    var _url2 = 'http://174.138.61.246:8080/support/dcreasons/$did';
    var http = createHttpClient();
    var response = await http.get(_url2);
    var reasons = await jsonCodec.decode(response.body);
    myReasonList = await reasons.toList();
    print('REASONS: '+ myReasonList.toString());


    return myReasonList;
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('ExpansionTile Test'),
      ),
      body: new ListView.builder(
        itemBuilder: _itemBuilder,
        itemCount: mycount,
      ),
    );
  }

  Widget _itemBuilder(BuildContext context, int index) {
    Exp exp = getExp(index);
    return new ListChild(exp: exp,);
  }

  Exp getExp(int index) {
    return new Exp(
      myDCList[index]['dname'],
      _getChildren(myDCList[index]['did']),
    );
    //return new Specialties.fromMap(mylist[index]);

  }
}

class Exp {
  Exp(this.title, [this.children]);
  final String title;
  final Future<List<Exp>> children;
}


class ListChild extends StatefulWidget {
  ListChild({Key key, this.exp}) : super(key: key);

  final Exp exp;
  @override
  State createState() => new ListChildState();
}

class ListChildState extends State<ListChild> {
  //PageStorageKey<ListChildState> _key = new PageStorageKey(ListChild);
  @override
  Widget build(BuildContext context) {
    return new ExpansionTile(
      key: new PageStorageKey(ListChild),
      title: new Text(widget.exp.title),
      children: <Widget>[
        new Text(widget.exp.children.title),
      ],
    );
  }
}