multiselection list view with data from DB - flutter

Question

I am trying to read data from postgresql, display in listview, select (single/multiple) displayed items and process further. Able to do with sample data but while displaying data from Postgres DB facing challenges at highlighted area. Any suggestions would be appreciated.
(I am trying to read data from postgresql, display in listview, select (single/multiple) displayed items and process further. Able to do with sample data but while displaying data from Postgres DB facing challenges at highlighted area. Any suggestions would be appreciated.)
**app_db.dart**
import 'package:postgres/postgres.dart';
class AppDatabase {
PostgreSQLConnection? connection;
PostgreSQLResult? _fetchSellerDataResult;
AppDatabase() {
connection = (connection == null || connection!.isClosed == true
? PostgreSQLConnection("10.0.2.2", 5432, "dev", username: "postgres", password: "admin")
: connection);
fetchDataFuture = [];
}
// Fetch Data Section
List<dynamic> fetchDataFuture = [];
Future<List<dynamic>> fetchSellerData() async {
try {
await connection!.open();
await connection!.transaction((fetchDataConn) async {
_fetchSellerDataResult = await fetchDataConn.query(
"select cust_id, cust_name, mmt, available_amount, false AS isSelected from api_positionstest2",
allowReuse: false,
timeoutInSeconds: 30,
);
if (_fetchSellerDataResult!.affectedRowCount > 0) {
fetchDataFuture = _fetchSellerDataResult!.toList(growable: true);
} else {
fetchDataFuture = [];
} });
} catch (exc) {
fetchDataFuture = [];
exc.toString();
}
return fetchDataFuture;
}}
**model_positions.dart**
import 'package:e2/Models/app_db.dart';
class ModelsPositions {
List<dynamic> sellerDataFuture = [];
Future<List<dynamic>> fetchSellerData() async {
sellerDataFuture = await AppDatabase().fetchSellerData();
return sellerDataFuture;
}}
**MasterPositions.dart**
class MasterPositions {
String custID;
String custName;
double mtm;
double availableCash;
bool isSelected = false;
MasterPositions(
{required this.custID,
required this.custName,
required this.mtm,
required this.availableCash});}
**master_control.dart**
import 'package:flutter/material.dart';
import 'package:e2/Models/model_positions.dart';
class MasterControl extends StatefulWidget {
const MasterControl({super.key});
#override
State<MasterControl> createState() => _MasterControlState();
}
class _MasterControlState extends State<MasterControl> {
List<MasterPositions> selectedContacts = [];
List<MasterPositions> fetchedPositions = [];
#override
void initState() {
super.initState();
}
#override
Widget build(BuildContext context) => Scaffold(
body: FutureBuilder<List<dynamic>>(
future: ModelsPositions().fetchSellerData(),
builder: (context, snapshot) {
final positions = snapshot.data ?? [];
switch (snapshot.connectionState) {
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
default:
if (snapshot.hasError) {
return Center(child: Text('Error while loading Master Positions screen'));
} else {
return buildPositions(positions);
} } }), );
Widget buildPositions(List<dynamic> positions) {
return ListView.builder(
physics: BouncingScrollPhysics(),
itemCount: positions.length,
itemBuilder: (context, index) {
final pos = positions[index];
final custID = pos.elementAt(0).toString();
final custName = pos.elementAt(1).toString();
final mtm = double.tryParse(pos.elementAt(2)) ?? 0.0;
final availableCash = double.tryParse(pos.elementAt(3)) ?? 0.0;
final isSelected = pos.elementAt(4);
return ListTile(
horizontalTitleGap: -5,
title: Card(
child: Row(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Expanded(
child: Column(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
Text(custID),
const SizedBox(height: 5),
Text(custName)],),),],),),
leading: isSelected
? Icon( Icons.check_circle, color: Colors.green[700],)
: const Icon(Icons.check_circle_outline, color: Colors.grey,),
onTap: () {
setState(() {
positions[index].elementAt(4) = !positions[index].elementAt(4); `**--> suggestion needed here**`
if (positions[index] == true) {
selectedContacts.add(
MasterPositions(custID: custID, custName: custName, mtm: mtm, availableCash: availableCash));
} else if (positions[index] == false) {
selectedContacts.removeWhere(
(element) => element.custID == pos[index].custID);
}}); }, );});}
}