Dropdown box value not updating in flutter

I am basically trying to implement a file navigation system using a column of dropdown boxes. The first box has 2 options: "random" and "choose".
once one of the options are selected, I have the code to use that string and get the next list of options for the next dropdown box. Once, an option is selected, I want to add a dropdown box that gives you the next set of options, and then once I choose an option from that box, I want to add another box with the next corresponding options and so on.

As seen below, I have 2 lists, one is a list of Strings containing the selected options, and one is a list of the dropdown boxes that are passed to the column widget. The value of the dropdown boxes is set to the value of the first item in the list of selected options (initially a list with one null value). in the onChanged property, I am updating the value from the null value to the selected value, and print statements indicate that the value is actually changing, but for some reason, the dropdown box is not showing an updated selection. I have not yet gotten to the part when I add new dropdown boxes.

The list of dropdown boxes is initially empty, but I add the first one in the build of the column widget if the dropdown list is initially empty.

Please help, Thank you!

P.S. Sorry about the random comments and messiness of code, I was using them to debug and I am still a Novice.

Here is the code that I implemented. It gives me a dropdown box and seems to update the values of leftDropDownBoxOptions but the value of the dropdown box does not change on screen.

class TrainingScreenRoute extends StatefulWidget {
... // <--- other variables
TrainingScreenRoute(this.user, this.currRelativePathLeft, this.currRelativePathMain){}
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return TrainingScreenRouteState(user, this.currRelativePathLeft, this.currRelativePathMain);
}
}
class TrainingScreenRouteState extends State<TrainingScreenRoute> {
... // <--- other variables
List<String?> leftDropDownBoxOptions = [null];
List<Widget> leftDropDownBoxes = [];
TrainingScreenRouteState(this.user, this.currRelPathLeft, this.currRelPathMain);
@override
Widget build(BuildContext context) {
... // <--- other variables
return MaterialApp(
home: Scaffold(
body: leftTrainPanel(context, currRelPathLeft),
),
);
}
Widget leftTrainPanel(BuildContext context, String currRelPathLeft) {
int curr_index = leftDropDownBoxes.length;
print("------------------>got to here");
print(leftDropDownBoxOptions);
if (curr_index == 0) { 
Widget firstOptBox = createDropDownBox(context, ["random", "choose"], add, 0);
print("here 5");
setState(() {
print("------------->box added");
leftDropDownBoxes.add(firstOptBox);
});
}
Widget createDropDownBox(BuildContext context, List<String> options, Function operation, int boxIndex) {
double screen_h = MediaQuery.of(context).size.height;
List<DropdownMenuItem<String>> menuItems = [];
for (String option in options) {
menuItems.add(DropdownMenuItem(child: Text(option, style: TextStyle(fontSize: screen_h/20)),value: option));
}
print("yolsssssssss");
return DropdownButton(
value: leftDropDownBoxOptions[0],
hint: Text('Select'),
items: menuItems,
onChanged: (String? value) {
setState(() {
leftDropDownBoxOptions[0] = value!;
//val = value;
print("yolo");
print(leftDropDownBoxOptions);
print(leftDropDownBoxes);
operation();
});
},
);
}
}

Ok so I'm not sure why, but I was able to fix the problem. the dropdown box widgets cannot be a state variable. Instead the information to create the dropdown box can be, but the box has to be created within the build.