Unknown LateInitializationError in Flutter - flutter

Question

I have a flutter widget which retrieves Json information from an API and displays a widget of that information. My initState is as follows:
class _BuildCardsWidgetState extends State<BuildCardsWidget> {
bool display = false;
late Resource _resource;
Future<Resource> fetchResource(Build build) async {
var url = Uri.parse(APIURL); <-actual url link hidden
final response = await http.get(url);
var resourceReturn = json.decode(response.body);
var resourceJson = resourceReturn[0]['resource'];
return Resource.fromJson(resourceJson, build);
}
#override
void initState() {
fetchResource(widget.build).then((value) =>
this.setState(() {
_resource = value;
display = true;
}));
super.initState();
}
#override
Widget build(BuildContext context) {
return ... <- _resource is used within build
However, whenever the program gets to the line
final response = await http.get(url);
This error is thrown:
The following LateError was thrown building BuildCardsWidget(dirty, state: _BuildCardsWidgetState#b3c7a):
LateInitializationError: Field '_resource' has not been initialized.
The thing that confuses me is this error flashes, but then right after the widget is correctly built and it runs smoothly. Any suggestions on how to fix this or on how to ignore this error since it does appear to work after the initial error?

Answer 1

Try to avoid using asynchronous functions inside initState, if it's not properly handled with await in a separate function, the widget won't load your data before build your widgets. A quick and simple way to solve this is to use a FutureBuilder().
class _BuildCardsWidgetState extends State<BuildCardsWidget> {
Future<Resource> fetchResource(Build build) async {
var url = Uri.parse(APIURL); <-actual url link hidden
var resourceReturn = json.decode(response.body);
var resourceJson = resourceReturn[0]['resource'];
return Resource.fromJson(resourceJson, build);
}
#override
Widget build(BuildContext context) {
return FutureBuilder<Resource>(
future: fetchResource(build),
builder: (context, snapshot) {
return SizedBox();
}
if(snapshot.hasError) {
/// Handle error
}
}
);
}
}