Я пытаюсь написать программу входа в систему, но мой TextField возвращает null

Question

Я пытаюсь написать программу входа в систему, но при смене пароля я должен проверить, в порядке ли текущий пароль, и мое имя пользователя, которое является текстовым полем, возвращает значение null, мое первое имя пользователя работает (при успешном входе в систему), но есть проблема со вторым, поэтому я действительно застрял в своем коде.

  

package sample;

import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.stage.Stage;

import javax.swing.*;
import java.io.IOException;
import java.sql.*;
import java.util.Optional;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.logging.Level;
import java.util.logging.Logger;


public class Controller {

    @FXML
    private PasswordField currentpassword;
    @FXML
    private PasswordField newPassword;


    @FXML
    private TextField userName;
    @FXML
    private PasswordField password;
    @FXML
    private Button loginButt;
    @FXML
    private GridPane mainfxml;

    Connection con = null;
    PreparedStatement preparedStatement;
    PreparedStatement savePrePared;
    PreparedStatement SidePrepared;


    public void initialize() {

    }

    @FXML
    public void loginsuccessful(ActionEvent event) {


        String query = "SELECT * FROM login WHERE username = ? " + " AND  password = ? ";

        try {
            con = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\mkara\\Desktop\\userpass\\javatest.db");
            String pass = password.getText();
            preparedStatement = con.prepareStatement(query);
            String uname = userName.getText();

            preparedStatement.setString(1, uname);
            preparedStatement.setString(2, pass);
            ResultSet resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {
                loginButt.setOnMouseClicked(mouseEvent -> {
                    try {

                        FXMLLoader fxmlLoader = new FXMLLoader();
                        fxmlLoader.setLocation(getClass().getResource("login_page.fxml"));
                        Scene scene = new Scene(fxmlLoader.load(), 600, 400);
                        Stage stage = new Stage();
                        stage.setTitle(uname + "'s Profile");
                        stage.setScene(scene);
                        stage.initOwner(mainfxml.getScene().getWindow());

                        stage.show();
                    } catch (IOException e) {
                        Logger logger = Logger.getLogger(getClass().getName());
                        logger.log(Level.SEVERE, "Failed to create new Window.", e);
                    }
                });
            } else {
                Alert alert = new Alert(Alert.AlertType.INFORMATION);
                alert.setTitle("faild ");
                alert.setHeaderText(null);
                alert.setContentText("your login was  faild try agin");
                alert.showAndWait();
                return;
            }
        } catch (SQLException e) {
            System.out.println(e.getMessage());
            e.printStackTrace();
        }

    }

    public void changepassword(ActionEvent event) {
        try {

            FXMLLoader fxmlLoader = new FXMLLoader();
            fxmlLoader.setLocation(getClass().getResource("passwordChange.fxml"));
            Scene scene = new Scene(fxmlLoader.load(), 600, 400);
            Stage stage = new Stage();
            stage.setTitle("Change your password");
            stage.setScene(scene);
            stage.show();


        } catch (IOException e) {
            Logger logger = Logger.getLogger(getClass().getName());
            logger.log(Level.SEVERE, "Failed to create new Window.", e);
        }


    }

    public void saveNewPass(ActionEvent event) {


        try {
            con = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\mkara\\Desktop\\userpass\\javatest.db");

            String cupass = currentpassword.getText();
            String newpass = newPassword.getText();
            System.out.println("Cupass" + cupass);
            System.out.println("newpass" + newpass);
            String uname = userName.getText();
            System.out.println(uname);

            String query = "SELECT password FROM login WHERE  username =" + uname;
            String insertNewPass = "UPDATE login set password = " + newpass + "WHERE username =" + uname;
            savePrePared = con.prepareStatement(query);
            ResultSet resultSet = preparedStatement.executeQuery();

            //if the field were blank
            if ((cupass == null) || (newpass == null)) {
                Alert alert = new Alert(Alert.AlertType.WARNING);
                alert.setTitle("Empty fields");
                alert.setContentText("You did not enter your passwords ");
                alert.setHeaderText(null);
                alert.showAndWait();
                return;
            }
            while (resultSet.next()) {
                String dbpass = resultSet.getString("password");
                if (dbpass.equals(cupass)) {
                    SidePrepared = con.prepareStatement(insertNewPass);
                    ResultSet resultSet1 = preparedStatement.executeQuery();
                    if (resultSet1.next()) {
                        Alert alert = new Alert(Alert.AlertType.INFORMATION);
                        alert.setTitle("Password changed!");
                        alert.setContentText("Your Password has changed!");
                        alert.setHeaderText(null);
                        alert.showAndWait();
                        return;

                    }

                }//if current pass is wrong
                else {
                    Alert alert = new Alert(Alert.AlertType.WARNING);
                    alert.setTitle("Wrong information!");
                    alert.setContentText("Your Current password is wrong ");
                    alert.setHeaderText(null);
alert.showAndWait();

                        return;

            }}

        } catch (SQLException e) {
            System.out.println(e.getMessage());
            e.printStackTrace();
        }

    }
    public void logout(ActionEvent event){
        Alert alert = new Alert(Alert.AlertType.CONFIRMATION);
        alert.setTitle("exite");
        alert.setContentText("Are you sure you want to exite? ");
        alert.setHeaderText(null);

            Optional<ButtonType> result = alert.showAndWait();

        if(result.isPresent() && (result.get() == ButtonType.OK)) {
            alert.close();
            Platform.exit();

        }else{
        return;
    }
    }
}

мой основной f xml

<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.control.PasswordField?>
<GridPane  fx:controller="sample.Controller"
          xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="10">
    <Label text="Username" GridPane.rowIndex="0" GridPane.columnIndex="0"/>
    <TextField  fx:id="userName" GridPane.rowIndex="0" GridPane.columnIndex="1"/>
    <Label text="Password" GridPane.rowIndex="1" GridPane.columnIndex="0"/>
    <PasswordField fx:id="password" GridPane.rowIndex="1" GridPane.columnIndex="1"/>

    <Button  fx:id="loginButt" text="Login" GridPane.rowIndex="2" GridPane.columnIndex="1" onAction="#loginsuccessful" />

</GridPane>

мой пароль смена f xml

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<GridPane xmlns:fx="http://javafx.com/fxml"
          fx:controller="sample.Controller" alignment="center" hgap="10" vgap="10">
    <Label text="Enter your Current Password:" GridPane.columnIndex="0" GridPane.rowIndex="0"/>
    <PasswordField  fx:id="currentpassword" GridPane.rowIndex="0" GridPane.columnIndex="1"/>
    <Label text="Enter your new password:" GridPane.columnIndex="0" GridPane.rowIndex="1"/>
    <PasswordField fx:id="newPassword" GridPane.rowIndex="1" GridPane.columnIndex="1"/>
    <Button text="Save" GridPane.rowIndex="5" GridPane.columnIndex="5" onAction="#saveNewPass"/>
</GridPane>

моя страница входа f xml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<GridPane   fx:controller="sample.Controller"
          xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="10">
    <Button text="Logout"  GridPane.rowIndex="0" GridPane.columnIndex="0"/>
    <Button text="Change your password" GridPane.rowIndex="3" GridPane.columnIndex="0" onAction="#changepassword"/>
</GridPane>

Main

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Login page");
        primaryStage.setScene(new Scene(root, 300, 275));
        primaryStage.show();
    }


    public static void main(String[] args) {
        launch(args);


        try {
            Connection con = DriverManager.getConnection("jdbc:sqlite:C:\\Users\\mkara\\Desktop\\userpass\\javatest.db");

            Statement statement = con.createStatement();

            statement.execute("CREATE TABLE IF NOT EXISTS login"
                    + "(username TEXT,password text)");
            //  statement.execute("INSERT INTO login(username,password)" + "VALUES('mahdi','123456')");


            ResultSet results = statement.executeQuery("SELECT * FROM  login");

            while (results.next()) {
                System.out.println(results.getString("username") + " "
                        + results.getString("password"));

            }
            results.close();
            statement.close();
            con.close();
        } catch (SQLException e) {
            System.out.println("something went wrong" + e.getMessage());
            e.printStackTrace();
        }
    }
}

, и у меня эта ошибка

Caused by: java.lang.NullPointerException