Flutter not retrieving variable new value while calling in another class

See more:

MySQL

Dart

Flutter

I have this StatefulWidget that supposed to retrieve data from MySQL database based on condition and add those retrieved values into an array so I can use the array values to be display on ListView. My Problem is that sometimes when the array (_fileValues) and _custUsername variable are either empty or not updated and no exception is thrown.

Here's my statefulwidget (main.dart)

String? _custUsername;
List<String> _fileValues = <String>[];

class cakeLogin extends StatefulWidget {
  @override
  cakeLoginPageMain createState() => cakeLoginPageMain(); 
}

class cakeLoginPageMain extends State<cakeLogin> {

  String? _CustEmailInit; 
  BuildContext? loginContext;

  List<String> _fileNameStores = <String>[];

  void callData() {
    // @ Get username based on user email and assign it to _custUsername variable
    UsernameGetter().Connection(_CustEmailInit!).then((UsernameValue) {
      _custUsername = UsernameValue!;
    });
    
    // @ Get item names based on the user username (_custUsername) and add them into
    // _fileNameStores
    NameGetter().Connection(_custUsername).then((NamesValues) {
      for(var _nameItems in NamesValues) {
        setState(() {
          _fileNameStores.add(_nameItems);
        });
      }
    });
    // @ Remove duplicates value and add them into main list (_fileValues)
    var _removeDuplicates = _fileNameStores.toSet().toList();
    for(var item in _removeNamesDupes) {
      setState(() {
       _fileValues.add(item);
      });
     }

  }
  
  @override
  Widget build(BuildContext context) {

    final _emailController = TextEditingController();

    return Scaffold(
      appBar: AppBar(
        title: Text("Login to App",
          style: TextStyle(
            fontSize: 18,
            color: setupFontCol,
            fontWeight: FontWeight.bold
          )),
        backgroundColor: setupThemeBar,
        centerTitle: true,
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(20),
        )
      ),
      backgroundColor: setupMainTheme,
      body: Padding(
        padding: EdgeInsets.all(20),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            TextFormField(
              controller: _emailController,
              style: TextStyle(color: Color.fromARGB(255, 214, 213, 213)),
              decoration: InputDecoration(
                border: OutlineInputBorder(
                  borderRadius: BorderRadius.circular(10),
                ),
                filled: true,
                hintStyle: TextStyle(color: Color.fromARGB(255, 197, 197, 197)),
                hintText: "Enter your email",
                fillColor: setupThemeBar
              ),
            ),

           SizedBox(height: 18),

           SizedBox(height: 25),

          SizedBox(
            height: 45,
            width: 500,
            child: ElevatedButton(
              style: 
                ElevatedButton.styleFrom(
                  primary: setupFontCol,
                  onPrimary: Colors.white,
                  shape: RoundedRectangleBorder(
                    borderRadius: BorderRadius.circular(10),
                  )
                ),
              onPressed: () {

                var _CustEmail = _emailController.text;

                if(_CustEmail.contains("@gmail.com") || _CustEmail.contains("@email.com")) {
                   if(_CustEmail != "") {
                          _CustEmailInit = _CustEmail;
                          loginContext = context;

                          _isFromLogin = true;
  
                          _fileValues.clear();
                          callData();

                    } else {
                      alertDialog("Please enter your email address",context);
                    }
                } else {
                    alertDialog("Email address is not valid",context);
                }
              },
              //color: setupFontCol,
              child: Text("Login",
                style: TextStyle(
                  color: Colors.white,
                  fontWeight: FontWeight.normal,
                  fontSize: 14,
                ))
              ),
            ),
          ],
        ),
      ),      
    );
  }
}

UsernameGetter class (This class will retrieve user Username from database table based on their email from textfield input)

When I print _usernameDetected from UsernameGetter class it returns the updated version of the returned string but when I assign the _custUsername to UsernameValue from main.dart it does not update and sometimes it returns null value.

import 'package:mysql_client/mysql_client.dart';
import 'dart:convert';
import 'dart:ffi';
import 'dart:typed_data';
import 'package:signuppage/main.dart' as main;
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class UsernameGetter {
  Future<String> Connection(String _custEmail) async {
    final conn = await MySQLConnection.createConnection(
      host: "",
      port: ,
      userName: "",
      password: "",
      databaseName: "",
    );

    await conn.connect();

    var _getUsernameQue = await conn.execute("SELECT CUST_USERNAME FROM information WHERE CUST_EMAIL = :email", 
    {
      "email": _custEmail
    });

    String? _usernameDetected;
    for(final _rowsOfEmail in _getUsernameQue.rows) {
      _usernameDetected = _rowsOfEmail.assoc()['CUST_USERNAME']!;
    }
    return await _usernameDetected!;
  }
}

NameGetter class (Retrieve user items names which are stored in text column)

For NameGetter class the same case happens as UsernameGetter. When I retrieve the values from main.dart and add the values into _fileValues list sometimes the values is empty and sometimes the value is not updated.

import 'package:mysql_client/mysql_client.dart';
import 'dart:convert';
import 'dart:ffi';
import 'dart:typed_data';
import 'package:signuppage/main.dart' as main;
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

class NameGetter {

  Future<List<String>> Connection(String _custUsername) async {
    final conn = await MySQLConnection.createConnection(
      host: "",
      port: ,
      userName: "",
      password: "",
      databaseName: "",
    );
    await conn.connect();

    var _getItemNames= await conn.execute("SELECT ITEM_NAMES FROM item_details WHERE CUST_USERNAME = :username",
      {
        "username": _custUsername
      });

    List<String>? _itemNamesValues= <String>[]; 
    for(var _rowsOfItemNames in _getItemNames.rows) {
      var _retrieveNames = await _rowsOfItemNames.assoc()['ITEM_NAMES']!;
      _itemNamesValues.add(_retrieveNames);
    }

    return await _itemNamesValues;
  }
}

I'm not sure where's my mistakes is and I'm pretty sure I made a lot of mistake and I need someone to help me figure it out. Especially on why the list and the variable are not updated/and is sometimes empty.

What I have tried:

Refer links:

Flutter ListView not updating

my list in flutter is not updating the problem in my code

Why variable value is not refreshing in flutter?