How to wait for value before calling method Flutter/Dart - flutter

Question

I am having a pretty hard time with certain actions in flutter. I currently have a method in an outside class that updates a db that my widget relies on for displaying info. I am correctly updating the values in the db and updating the UI correctly. BUT I am having a hard time getting an input first, THEN having that method function. I have tried having it all in the same body and no dice, I have tried to have the addStock method show the input and does not work. The only thing that has been a ban-aid has been to use Navigator.push to the screen again or using a time delayed. Both have produced undesired consequences. I have also tried having the addStock method inside the displayAmountToADD on pressing okay and does not update UI.
//a button inside the UI
onPressed: () async {
displayAmountToAdd(context, index);
setState(() {});
},
....
Future<void> displayAmountToAdd(
BuildContext context,
int index,
) async {
final _textFieldController = TextEditingController();
double materialKG = 0;
showDialog(
context: context,
builder: (context) {
return AlertDialog(
title: Text('Enter amount to add'),
content: Row(
children: <Widget>[
Expanded(
child: TextField(
onChanged: (materialQuanity) {
materialKG = double.parse(materialQuanity);
},
controller: _textFieldController,
decoration: InputDecoration(hintText: "KG"),
),
),
],
),
actions: <Widget>[
TextButton(
child: Text('OK'),
onPressed: () {
materialKG = double.parse(_textFieldController.text);
addStock(context, mapM[index]['quanity'], mapM[index]['name'],
materialKG);
Navigator.pop(context);
},
),
TextButton(
child: Text("Cancel"),
onPressed: () {
Navigator.pop(context);
})
],
);
},
);
//return Future.delayed(Duration(seconds: 4),()=>materialKG); //TRYING TO AVOID THIS
}
//outside the ui file
addStock(
BuildContext context,
double currentQuanity,
String name,
double amountToAdd
) async {
//final db = await database;
double newStock;
late double materialKG;
newStock=currentQuanity+amountToAdd;
await db.rawUpdate(
'UPDATE materials SET quanity = $newStock WHERE name = "$name" ');
mapM = await db.query('materials'); //update values
//the following is only because setState is not working properly on other screen
ScaffoldMessenger.of(context).showSnackBar(SnackBar(
content: Text("Added $amountToAdd KG to $name"),
));
}

Answer 1

displayAmountToAdd and showDialog method are future. Use await before theses to hold method to finish.
A sample example:
const oneSecond = Duration(seconds: 1);
// ···
Future<void> printWithDelay(String message) async {
await Future.delayed(oneSecond);
print(message);
}
Learn more about async-await.