Flutter динамически устанавливает детей

Поэтому я хочу динамически устанавливать дочерние элементы моего GridView, чтобы я мог устанавливать их, когда захочу. На данный момент это весь класс.

import 'dart:convert';
import 'dart:io';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter_app/CustomColors.dart';
import 'package:flutter_app/quote/Quote.dart';
import 'package:flutter_app/quote/QuoteView.dart';
import 'package:flutter_app/section/Section.dart';
import 'package:flutter_app/quote/QuoteData.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.

  static List<QuoteData> data = [];

  _readJson() async {
    data.clear();
    var url = 'https://www.dropbox.com/s/7k280ca5dktlhoo/quotes.json?dl=1';
    var httpClient = new HttpClient();
    httpClient.getUrl(Uri.parse(url)).then((HttpClientRequest request) {
      return request.close();
    }).then((HttpClientResponse response) {
      response.transform(utf8.decoder).listen((contents) {
        List<Map> decoded = JSON.decode(contents);
        decoded.forEach((m) {
          String url = m["url"];
          String title = m["title"];
          String sectionString = m["section"];
          Section section;
          for (Section element in Section.values) {
            if (element.toString() == "Section." + sectionString) {
              section = element;
            }
          }
          List<Quote> quotes = m["quotes"];
          data.add(new QuoteData(url, title, section, quotes));
        });
      });
    });
  }

  @override
  Widget build(BuildContext context) {
    _readJson();
    return new MaterialApp(
      title: 'Quotes',
      theme: new ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: CustomColors.black,
      ),
      home: new MyHomePage(title: 'Quotes'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

  static Section currentSection = Section.movies;

  void _onTileClicked(QuoteData quote) {
    Navigator.push(context,
        new MaterialPageRoute(builder: (context) => new QuoteView(quote)));
  }

  List<Widget> _getTiles(Section section) {
    final List<Widget> tiles = <Widget>[];
    for (var i in MyApp.data) {
      if (i.section != section) {
        continue;
      }
      tiles.add(new GridTile(
          child: new InkResponse(
        enableFeedback: true,
        child: new Image.network(
          i.url,
          fit: BoxFit.cover,
        ),
        onTap: () => _onTileClicked(i),
      )));
    }
    return tiles;
  }

  @override
  Widget build(BuildContext context) {
    var size = MediaQuery.of(context).size;
    final double itemHeight = (size.height - kToolbarHeight - 24) / 2;
    final double itemWidth = size.width / 2;
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return new Scaffold(
      appBar: new AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: new Text(currentSection
                .toString()
                .replaceAll("Section.", "")
                .substring(0, 1)
                .toUpperCase() +
            currentSection.toString().replaceAll("Section.", "").substring(1)),
      ),
      body: new Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: new GridView.count(
            crossAxisCount: 2,
            childAspectRatio: (itemWidth / itemHeight),
            padding: const EdgeInsets.all(4.0),
            mainAxisSpacing: 4.0,
            crossAxisSpacing: 4.0,
            children: _getTiles(currentSection)),
      ),
    );
  }
}

Итак, прямо сейчас при запуске он запускает приложение, но MyApp.data пуст, потому что должен быть прочитан json, поэтому GridView будет пустым, когда я обновляю приложение, GridView не будет пустым, потому что MyApp.data не будет больше быть пустым. Я хочу иметь возможность устанавливать дочерние элементы после того, как json будет прочитан, также мне нужно иметь возможность изменять его динамически, потому что я добавлю функцию для переключения разделов.

То же самое и с заголовком, мне также нужно иметь возможность динамически изменять его при переключении разделов.