Get dropdown values based on another dropdown value in flutter - flutter

Question

I have a url that returns a json of companies, i use the list of companies to fill a dropdown. there is another url with a parameter that returns a list of warehouses. The second method that gets the warehouses returns an empty json.
Here is the code that gets the companies. This is working alright
String? _mySelection;
final String url = "http://url:8000/companies"
Future<String> getCompanies() async {
var res = await http
.get(Uri.parse(url), headers: {
'Content-Type': 'application/json'
});
var resBody = json.decode(res.body)["data"]; // data = map["data"];
print(resBody);
setState(() {
data = resBody;
});
print(res);
return "Sucess";
}
The code that gets the warehouses is similar.
Future<String> getWarehouses(company) async {
late String warehousesUrl = "http://myWarehouseurl?company=$company";
var warehouseRes = await http
.get(Uri.parse(warehousesUrl), headers: {
'Content-Type': 'application/json'
});
var warehouseResBody = json.decode(warehouseRes.body)["data"]; // data = map["data"];
print(warehouseResBody);
setState(() {
warehouseData = warehouseResBody;
});
print(warehouseRes);
return "Sucess";
}
And my initState method
#override
void initState() {
super.initState();
this.getCompanies();
this.getWarehouses(_mySelection);
}
The dropdowns
new DropdownButton(
items: data.map((item) {
return new DropdownMenuItem(
child: new Text(item['company_name']),
value: item['company_name'].toString(),
);
}).toList(),
onChanged: (newVal) {
setState(() {
_mySelection = newVal.toString();
getWarehouses(_mySelection);
});
},
value: _mySelection,
),
_mySelection != "" ? DropdownButton(
items: warehouseData.map((item) {
return new DropdownMenuItem(
child: new Text(item['warehouse_name']),
value: item['name'].toString(),
);
}).toList(),
onChanged: (newVal) {
setState(() {
_mySelection = newVal.toString();
});
},
value: _mySelection,
) : Container(),
I am not sure why i am unable to get the values for the second dropdown, when i call the method to get the values for the warehouse in the onchange method in the companies dropdown, the data from the warehouses are printed to the console, but the app crushes.

Answer 1

I think you miss the async/await, lets try
new DropdownButton(
items: data.map((item) {
return new DropdownMenuItem(
child: new Text(item['company_name']),
value: item['company_name'].toString(),
);
}).toList(),
onChanged: (newVal) async{ // here need the change
setState(() {
_mySelection = newVal.toString();
await getWarehouses(_mySelection); // also here add the await
});
},
value: _mySelection,
),