Flutter #3: I have some async problem in flutter - flutter

Question

I have a piece of code to scan and read device information. I have printed the elements in the list in onScan function, however I don't know how to get that information and put it in a listview.
Can someone help me?
List<Data> listDevice = [];
Future<void> getData() async {
var apiEndpoint = TTAPI.shared;
await apiEndpoint.devideScan(((data) => onScan(data)));
}
Future<void> onScan(dynamic data) async {
var dataResponse = DataResponse.fromJson(data);
print(dataResponse.toJson());
List<dynamic> dt = jsonDecode(jsonEncode(dataResponse.data).toString());
dt.forEach((element) {
var item = Data.fromJson(element);
print(item.modelName);
listDevice.add(item);
});
var connectRequest = {
'serialNumber': 'DEVICE_SERIAL',
'modelName': 'DEVICE_MODEL',
'ipAddr': 'DEVICE_IP'
};
var apiEndpoint = TTAPI.shared;
await apiEndpoint.connectDevice(connectRequest);
}
Future<List<Data>> getList() async {
return listDevice;
}
You can see more of my code here: https://docs.google.com/document/d/1ntxaDpyNCLD1MyzJOTmZsrh7-Jfim8cm0Va86IQZGww/edit?usp=sharing

Answer 1

As for the current code structure, listDevice is populated inside Future. So you can call setState to update the UI after getting the list at the end of onScan.
Future<void> getData() async {
var apiEndpoint = TTAPI.shared;
await apiEndpoint.devideScan(((data) => onScan(data)));
setState((){});
}
But it would be great to use FutureBuilder and return list from getData.
Current question pattern example
class TextFW extends StatefulWidget {
const TextFW({super.key});
#override
State<TextFW> createState() => _TextFWState();
}
class _TextFWState extends State<TextFW> {
//for current question way
List<int> listDevice = [];
Future<void> getData() async {
await Future.delayed(Duration(seconds: 2));
/// others async method
listDevice = List.generate(10, (index) => index);
setState(() {}); //here or `getData().then()`
}
#override
void initState() {
super.initState();
getData();
// or this getData().then((value) => setState((){}));
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: ListView.builder(
itemCount: listDevice.length,
itemBuilder: (context, index) => ListTile(
title: Text("${listDevice[index]}"),
),
),
);
}
}
Using FutureBuilder
class TextFW extends StatefulWidget {
const TextFW({super.key});
#override
State<TextFW> createState() => _TextFWState();
}
class _TextFWState extends State<TextFW> {
/// method will provide data by scanning
Future<List<int>> getData() async {
await Future.delayed(Duration(seconds: 2));
return List.generate(10, (index) => index);
}
late final fututre = getData();
#override
Widget build(BuildContext context) {
return Scaffold(
body: FutureBuilder<List<int>>(
future: fututre,
builder: (context, snapshot) {
if (snapshot.hasError) {
return Text("${snapshot.error}");
}
if (snapshot.hasData) {
final listDevice = snapshot.data;
return ListView.builder(
itemCount: listDevice?.length,
itemBuilder: (context, index) => ListTile(
title: Text("${listDevice![index]}"),
),
);
}
return CircularProgressIndicator();
},
),
);
}
}