JavaFX控制器FXMLLoader.load（getClass（）。getResource（））;

Question

我有一个适用于FXML文件的应用程序。每次我想加载另一个FXML文件，我得到一个我的Controller类的新实例。但我不想那样。我该如何防止这种情况？

例如：我刚刚登录了我的login.fxml文件，现在需要关闭login.fxml文件并需要显示manageBanks.fxml文件。我编程的是它查看当前不是NULL的AnchorPane并从该窗格中获取窗口，因此我可以关闭该阶段。然后我加载我的控制器中的新.fxml文件。但每次我加载一个新的.fxml文件时，应用程序都会创建一个新的控制器实例。但是我在Controller类中有一个Client类的实例（在构造函数中设置），我不希望每次都更新该实例。我只想要一个控制器可以与之交谈的Client类的实例。

这是我的Controller类。在这个类的底部是我初始化新阶段的方法：

public class Controller {
public TextField tbIban;
public TextField tbFirstName;
public TextField tbLastName;
public TextField tbPostalCode;
public TextField tbHouseNumber;
public TextField tbEmail;
public TextField tbBankName;
public TextField tbShortcut;
public TextField tbEuroIn;
public TextField tbCentIn;
public TextField tbCentOut;
public TextField tbEuroOut;
public TextField tbEuroAmount;
public TextField tbCentAmount;
public TextField tbNameReceiver;
public TextField tbIbanReceiver;
public TextArea tbDescription;
public PasswordField tbPassword;
public PasswordField tbRepeatPassword;
public Label lbName;
public Label lbIban;
public Label lbAmount;
public TableView tabelTransactions;
public TableView tabelAddresses;
public TableView tabelBanks;
public DatePicker dtpDateOfBirth;
public CheckBox cbAddToAddressBook;
public ComboBox cmbbank;
public AnchorPane screenEditAccount;
public AnchorPane screenAddressBook;
public AnchorPane screenAddressBookTransaction;
public AnchorPane screenBankAccount;
public AnchorPane screenCreateBank;
public AnchorPane screenCreateBankAccount;
public AnchorPane screenLimits;
public AnchorPane screenLogin;
public AnchorPane screenManageBanks;
public AnchorPane screenNewTransaction;

private Client client;

public Controller() {
    try {
        client = new Client();
        System.out.println("Client: Client created");
    } catch (RemoteException e) {
        System.out.println("Client: Cannot create Client");
        System.out.println("Client: RemoteException: " + e.getMessage());
        System.exit(0);
    }
}

public void login() {
    String iban = tbIban.getText();
    String password = tbPassword.getText();
    try {
        if (client.login(iban, password)){
            if (iban.equals("admin")) {
                changeScreenTo(Screens.MANAGEBANKS);
            } else {
                changeScreenTo(Screens.BANKACCOUNT);
            }
        } else {
            showErrorMessage("Wrong username or password.");
        }
    } catch (RemoteException e) {
        showErrorMessage(e.getMessage());
    }
}

public void logoutClient() {
    try {
        client.logout();
        changeScreenTo(Screens.LOGIN);
    } catch (RemoteException e) {
        showErrorMessage(e.getMessage());
    }
}

public void logoutAdmin() {
    try {
        client.logout();
        changeScreenTo(Screens.LOGIN);
    } catch (RemoteException e) {
        showErrorMessage(e.getMessage());
    }
}

public void cancelToLogin() {
    changeScreenTo(Screens.LOGIN);
}

public void createBank() {
    String name = tbBankName.getText();
    String shortcut = tbShortcut.getText();
    try {
        if (client.createBank(name, shortcut)){
            changeScreenTo(Screens.MANAGEBANKS);
        } else {
            showErrorMessage("Bank name or shortcut already excist.");
        }
    } catch (RemoteException e) {
        showErrorMessage(e.getMessage());
    }
}

public void deleteBank() {
    String bank = String.valueOf(tabelBanks.getSelectionModel().getSelectedItem());
    String[] bankParts = bank.split(";");
    String bankName = bankParts[0];
    client.deleteBank(bankName);
}

public void createBankAccount() {
    String password = tbPassword.getText();
    String passwordRepeat = tbRepeatPassword.getText();
    String firstName = tbFirstName.getText();
    String lastName = tbLastName.getText();
    String postalCode = tbPostalCode.getText();
    int houseNumber = Integer.parseInt(tbHouseNumber.getText());
    Date dateOfBirth = Date.from(dtpDateOfBirth.getValue().atStartOfDay().atZone(ZoneId.systemDefault()).toInstant());
    String email = tbEmail.getText();
    String bankName = cmbbank.getValue().toString();
    if (password.equals(passwordRepeat) && !password.equals("")){
        if (!firstName.equals("") && !lastName.equals("") && !postalCode.equals("") && houseNumber != 0 && dateOfBirth.before(new Date()) && !email.equals("") && !bankName.equals("")){
            try {
                if (client.createBankAccount(bankName, password, firstName, lastName, postalCode, houseNumber, dateOfBirth, email)){
                    changeScreenTo(Screens.BANKACCOUNT);
                } else {
                    showErrorMessage("Something went wrong with creating your account.");
                }
            } catch (RemoteException e) {
                showErrorMessage(e.getMessage());
            }
        } else {
            showErrorMessage("Personal details are not valid or there is no bank selected.");
        }
    } else {
        showErrorMessage("Password can not be empty or is not the same as repeated password.");
    }
}

public void editBankAccount() {
    String password = tbPassword.getText();
    String passwordRepeat = tbRepeatPassword.getText();
    String firstName = tbFirstName.getText();
    String lastName = tbLastName.getText();
    String postalCode = tbPostalCode.getText();
    int houseNumber = Integer.parseInt(tbHouseNumber.getText());
    Date dateOfBirth = Date.from(dtpDateOfBirth.getValue().atStartOfDay().atZone(ZoneId.systemDefault()).toInstant());
    String email = tbEmail.getText();
    if (password.equals(passwordRepeat) && !password.equals("")){
        if (!firstName.equals("") && !lastName.equals("") && !postalCode.equals("") && houseNumber != 0 && dateOfBirth.before(new Date()) && !email.equals("")){
            try {
                client.editBankAccount(password, firstName, lastName, postalCode, houseNumber, dateOfBirth, email);
                changeScreenTo(Screens.BANKACCOUNT);
            } catch (RemoteException e) {
                showErrorMessage(e.getMessage());
            }
        } else {
            showErrorMessage("Personal details are not valid.");
        }
    } else {
        showErrorMessage("Password can not be empty or is not the same as repeated password.");
    }
}

public void deleteBankAccount() {
    try {
        client.deleteBankAccount();
        changeScreenTo(Screens.LOGIN);
    } catch (RemoteException e) {
        showErrorMessage(e.getMessage());
    }
}

public void cancelToBankAccount() {
    changeScreenTo(Screens.BANKACCOUNT);
}

public void editBankAccountsLimits() {
    double limitIn = Double.parseDouble(tbEuroIn.getText() + "," + tbCentIn.getText());
    double limitOut = Double.parseDouble(tbEuroOut.getText() + "," + tbCentOut.getText());
    if (limitIn > 0 && limitOut > 0){
        client.editBankAccountsLimits(limitIn, limitOut);
        changeScreenTo(Screens.BANKACCOUNT);
    } else {
        showErrorMessage("Limits can not be 0.");
    }
}

public void deleteBankAccountsAddress() {
    Address address = (Address) tabelAddresses.getSelectionModel().getSelectedItem();
    client.deleteBankAccountsAddress(address);
}

public void makeBankAccountsTransaction() {
    double amount = Double.parseDouble(tbEuroAmount.getText() + "," + tbCentAmount.getText());
    String nameReceiver = tbNameReceiver.getText();
    String ibanReceiver = tbIbanReceiver.getText();
    String description = tbDescription.getText();
    boolean addToAddress = cbAddToAddressBook.isSelected();
    if (amount > 0 && !nameReceiver.equals("") && !ibanReceiver.equals("")){
        client.makeBankAccountsTransaction(amount, nameReceiver, ibanReceiver, description, addToAddress);
        changeScreenTo(Screens.BANKACCOUNT);
    } else {
        showErrorMessage("Amount and receiver details can not be empty.");
    }
}

public void chooseAddress() {
    Address address = (Address) tabelAddresses.getSelectionModel().getSelectedItem();
    tbNameReceiver.setText(address.getName());
    tbIbanReceiver.setText(address.getIban());
    changeScreenTo(Screens.NEWTRANSACTION);
}

public void makeBankAccountsRequest() {
    double amount = Double.parseDouble(tbEuroAmount.getText() + "," + tbCentAmount.getText());
    String nameReceiver = tbNameReceiver.getText();
    String ibanReceiver = tbIbanReceiver.getText();
    String description = tbDescription.getText();
    boolean addToAddress = cbAddToAddressBook.isSelected();
    if (amount > 0 && !nameReceiver.equals("") && !ibanReceiver.equals("")){
        client.makeBankAccountsRequest(amount, nameReceiver, ibanReceiver, description, addToAddress);
        changeScreenTo(Screens.BANKACCOUNT);
    } else {
        showErrorMessage("Amount and receiver details can not be empty.");
    }
}

public void openCreateAccount() {
    changeScreenTo(Screens.CREATEBANKACCOUNT);
}

public void openAccount() {
    changeScreenTo(Screens.ACCOUNT);
}

public void openLimits() {
    changeScreenTo(Screens.LIMITS);
}

public void openAddressBook() {
    changeScreenTo(Screens.ADDRESSBOOK);
}

public void openAddressBookTransaction() {
    changeScreenTo(Screens.ADDRESSBOOKTRANSACTION);
}

public void openTransaction() {
    changeScreenTo(Screens.NEWTRANSACTION);
}

public void openCreateBank() {
    changeScreenTo(Screens.CREATEBANK);
}

private void initAccountScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/account.fxml"));
    stage.setTitle("Account");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.BANKACCOUNT));
    stage.show();
}

private void initAddressBookScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/addressBook.fxml"));
    stage.setTitle("Address Book");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.BANKACCOUNT));
    stage.show();
}

private void initAddressBookTransactionScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/addressBookTransaction.fxml"));
    stage.setTitle("Address Book");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.NEWTRANSACTION));
    stage.show();
}

private void initBankAccountScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/bankAccount.fxml"));
    stage.setTitle("Bank Account");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> logoutClient());
    stage.show();
}

private void initCreateBankScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/createBank.fxml"));
    stage.setTitle("Create Bank");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.MANAGEBANKS));
    stage.show();
}

private void initCreateBankAccountScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/createBankAccount.fxml"));
    stage.setTitle("Create Bank Account");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.LOGIN));
    stage.show();
}

private void initLimitsScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/limits.fxml"));
    stage.setTitle("Limits");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.BANKACCOUNT));
    stage.show();
}

private void initLoginScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/login.fxml"));
    stage.setTitle("Login");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> System.exit(0));
    stage.show();
}

private void initManageBanksScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/manageBanks.fxml"));
    stage.setTitle("Manage Banks");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> logoutAdmin());
    stage.show();
}

private void initnewTransactionScreen() throws IOException {
    Stage stage = new Stage();
    Parent root = FXMLLoader.load(getClass().getResource("Screens/newTransaction.fxml"));
    stage.setTitle("New Transaction");
    stage.setResizable(false);
    stage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    stage.setScene(new Scene(root));
    stage.setOnCloseRequest(event -> changeScreenTo(Screens.BANKACCOUNT));
    stage.show();
}

private void showErrorMessage(String message){
    Alert alert = new Alert(Alert.AlertType.INFORMATION);
    alert.setTitle("ERROR!");
    alert.setHeaderText(null);
    alert.setContentText(message);
    alert.showAndWait();
}

private void changeScreenTo(Screens screen) {
    if (screenEditAccount != null) {
        Stage currentStage = (Stage) screenEditAccount.getScene().getWindow();
        currentStage.close();
    } else if (screenAddressBook != null) {
        Stage currentStage = (Stage) screenAddressBook.getScene().getWindow();
        currentStage.close();
    } else if (screenAddressBookTransaction != null) {
        Stage currentStage = (Stage) screenAddressBookTransaction.getScene().getWindow();
        currentStage.close();
    } else if (screenBankAccount != null) {
        Stage currentStage = (Stage) screenBankAccount.getScene().getWindow();
        currentStage.close();
    } else if (screenCreateBank != null) {
        Stage currentStage = (Stage) screenCreateBank.getScene().getWindow();
        currentStage.close();
    } else if (screenCreateBankAccount != null) {
        Stage currentStage = (Stage) screenCreateBankAccount.getScene().getWindow();
        currentStage.close();
    } else if (screenLimits != null) {
        Stage currentStage = (Stage) screenLimits.getScene().getWindow();
        currentStage.close();
    } else if (screenLogin != null) {
        Stage currentStage = (Stage) screenLogin.getScene().getWindow();
        currentStage.close();
    } else if (screenManageBanks != null) {
        Stage currentStage = (Stage) screenManageBanks.getScene().getWindow();
        currentStage.close();
    } else if (screenNewTransaction != null) {
        Stage currentStage = (Stage) screenNewTransaction.getScene().getWindow();
        currentStage.close();
    }

    try {
        switch (screen) {
            case ACCOUNT:
                initAccountScreen();
                break;
            case ADDRESSBOOK:
                initAddressBookScreen();
                break;
            case ADDRESSBOOKTRANSACTION:
                initAddressBookTransactionScreen();
                break;
            case BANKACCOUNT:
                initBankAccountScreen();
                break;
            case CREATEBANK:
                initCreateBankScreen();
                break;
            case CREATEBANKACCOUNT:
                initCreateBankAccountScreen();
                break;
            case LIMITS:
                initLimitsScreen();
                break;
            case LOGIN:
                initLoginScreen();
                break;
            case MANAGEBANKS:
                initManageBanksScreen();
                break;
            case NEWTRANSACTION:
                initnewTransactionScreen();
                break;
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

这是我的主要课程：

public class ClientMain extends Application {

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

@Override
public void start(Stage primaryStage) throws Exception {
    Parent root = FXMLLoader.load(getClass().getResource("Screens/login.fxml"));
    primaryStage.setTitle("Login");
    primaryStage.setResizable(false);
    primaryStage.getIcons().add(new Image("file:assets/ideal_logo.jpg"));
    primaryStage.setScene(new Scene(root));
    primaryStage.setOnCloseRequest(event -> System.exit(0));
    primaryStage.show();
}
}

Answer 1

每次加载FXML文件时，都会获得FXML文件中定义的UI元素的新实例。例如，您的FXML文件显然有大量<TextField>个元素;对于每个<TextField>元素，每次加载FXML时都会创建一个新的TextField实例。

由于控制器通常具有对FXML文件中定义的UI元素的引用，和/或具有特定于这些元素的事件处理程序，因此控制器实例特定于实例FXMLLoader.load()的特定调用加载的UI的em>。

因此，在从多个FXMLLoader.load()调用加载的多个UI之间共享单个控制器实例完全没有意义。每个应该有一个不同的控制器实例，这是默认行为。