When launching the application the string appears as null - json

Question

As the title has said, whenever I run the flutter application in my phone (debug mode atm, I don't know if it will work correctly in release mode). The dndguide.toString() appears as null. However, upon a hot reload the string appears normally. Is there a way to avoid this and make it work correctly upon launching? I suspect I put the loadjson() call in the wrong location, but I've tried shaping the code so that the function is called in different areas and no success.
Here is the code for the application:
import 'package:flutter/material.dart';
import 'dart:async' show Future;
import 'package:flutter/services.dart' show rootBundle;
import 'dart:convert';
void main() => runApp(MyApp());
var dndguide;
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
home: MyHomePage(),
);
}
}
class MyHomePage extends StatefulWidget {
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
Future<String> _loadAsset() async {
return await rootBundle.loadString('assets/data/HDARG.json');
}
Future loadjson() async {
String jsonString = await _loadAsset();
final jsonResponse = json.decode(jsonString);
dndguide = jsonResponse;
}
#override
Widget build(BuildContext context) {
loadjson();
var scrollcontroller;
return Scaffold(
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Container(
height: MediaQuery.of(context).size.height - 24,
margin: EdgeInsets.only(top: 24.0),
width: MediaQuery.of(context).size.width * .90,
child: SingleChildScrollView(
physics: BouncingScrollPhysics(),
controller: scrollcontroller,
scrollDirection: Axis.vertical,
child: Text(dndguide.toString()),
),
),
],
),
),
);
}
}

Answer 1

The json response is called asynchronously, which why the first time it gives null and after hot reloading it appears successfully. You should put some placeholder value into your dndguide variable or call the json in the initState() function of your _MyHomePageState instead of calling it during build process:
#override
void initState() {
super.initState();
loadjson();
}