关于java：JavaFX登录隐藏按钮

//Login for employee
@FXML
private TextField textUsername;

@FXML
private PasswordField textPassword;

@FXML
private ChoiceBox<String> EmpSelect;

Stage dialogStage = new Stage();
Scene scene;

Connection connection = null;
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;

public LoginController() {
    connection = sqlDatabaseConnection.connectdb();
}

//Login for employee
@FXML
private void handleButtonAction(ActionEvent event) {
    String username = textUsername.getText().toString();
    String password = textPassword.getText().toString();
    String function = EmpSelect.getValue().toString();
    String sql ="SELECT * FROM Employee WHERE username = ? and password = ? and function = ?";

    try {
        preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setString(1, username);
        preparedStatement.setString(2, password);
        preparedStatement.setString(3, function);
        resultSet = preparedStatement.executeQuery();

        if (!resultSet.next()) {
            infoBox("Enter Correct Username and Password","Failed", null);
        } else {

            if ("Employee".equals(function)) {
                infoBox("Login Successfull","Success", null);
                FXMLDocumentController controller = new FXMLDocumentController();
                controller.newAnchorpane("WorkerHomescreen", paneLogin);
            } else if ("Manager".equals(function)) {
                infoBox("Login Successfull","Success", null);
                FXMLDocumentController controller = new FXMLDocumentController();
                controller.newAnchorpane("WorkerHomescreen", paneLogin);
            }
        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static void infoBox(String infoMessage, String titleBar, String headerMessage) {
    Alert alert = new Alert(AlertType.INFORMATION);
    alert.setTitle(titleBar);
    alert.setHeaderText(headerMessage);
    alert.setContentText(infoMessage);
    alert.showAndWait();
}

Connection connection = null;
public WorkerHomescreenController() {
    connection = sqlDatabaseConnection.connectdb();
}

@Override
public void initialize(URL url, ResourceBundle rb) {
    String Check ="SELECT * FROM Employee WHERE function = 'employee'";
    but4.setVisible(false);
}

<VBox xmlns="http://javafx.com/javafx" xmlns:fx="http://javafx.com/fxml" fx:controller="sample.WorkerController">
    <children>
        <Label text="Worker"/>
        <Button text="Different Action Button" onAction="#handleDifferentActionButton"/>
        <Button text="General Action Button" onAction="#handleGeneralActionButton"/>
    </children>
</VBox>

<VBox xmlns="http://javafx.com/javafx" xmlns:fx="http://javafx.com/fxml" fx:controller="sample.ManagerController">
    <children>
        <Label text="Manager"/>
        <Button text="Manager Only Button" onAction="#handleManagerButton"/>
        <Button text="Different Action Button" onAction="#handleDifferentActionButton"/>
        <Button text="General Action Button" onAction="#handleGeneralActionButton"/>
    </children>
</VBox>

public class WorkerController {

    @FXML
    protected void initialize() {

    }

    @FXML
    protected void handleDifferentActionButton(ActionEvent event) {

    }

    @FXML
    protected void handleGeneralActionButton(ActionEvent event) {

    }
}

public class ManagerController extends WorkerController {

    @FXML
    @Override
    protected void initialize() {
        super.initialize();
    }

    @FXML
    protected void handleManagerButton(ActionEvent event) {

    }

    @FXML
    @Override
    protected void handleDifferentActionButton(ActionEvent event) {

    }
}

public class Controller {
    private static final String WORKER ="/sample/worker_homescreen.fxml";
    private static final String MANAGER ="/sample/manager_homescreen.fxml";

    @FXML
    private void handleLoginButton() {
        ...

        if (!resultSet.next()) {
            infoBox("Enter Correct Username and Password","Failed", null);
        } else {
            if ("Employee".equals(function)) {
                infoBox("Login Successfull","Success", null);
                showMainView(getClass().getResource(WORKER));

            } else if ("Manager".equals(function)) {
                infoBox("Login Successfull","Success", null);
                showMainView(getClass().getResource(MANAGER));
            }
        }
    }

    private void showMainView(URL url) {
        try {
            Parent parent = FXMLLoader.load(url);

            Stage stage = new Stage();
            stage.setScene(new Scene(parent, 800, 600));
            stage.show();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}