Initialize a variable with local database value - sqlite

Question

I want to initialize a variable with a value that I have in my local sql database. This is the code:
class _SettingsState extends State<Settings>{
String morning = 'empty';
#override
void initState() {
super.initState();
initAsync();
}
void initAsync() async{
morning = await DatabaseHelper.instance.queryOrario(1);
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Container(
child: Text(morning),
),
);
}
The problem is that when I first arrive on this page, I have this error:
A non-null String must be provided to a Text widget.
referred to the line: child: Text(morning),
Then, when I hot reload the page, the code works fine. Why? What am I doing wrong? There is a way to do what I want to do?

Answer 1

(I'm assuming that morning's default value of 'empty' is something you added to your code before posting it here, and it's actuall default value is null. Otherwise, it would make no sense for you to be getting the error you are getting.)
The problem is that your widget is initializing and building before the future has a chance to finish. By the time you have assigned a value for morning, the widget has already been built. As such, when the widget does build, morning is still null. And Flutter heavily frowns on giving a null value to a Text widget.
Instead of depending on a race condition (where two parts of your code are racing to complete first and you are hoping they will complete in a particular order), use a FutureBuilder so you can safely execute futures and have your widget update itself when they are complete:
class _SettingsState extends State<Settings>{
#override
void initState() {
super.initState();
}
Future<String> initAsync() async {
String result = await DatabaseHelper.instance.queryOrario(1);
return result;
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: FutureBuilder<String>(
future: initAsync(),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return CircularProgressIndicator();
}
return Text(snapshot.data);
},
),
);
}
}