我想访问JTextField，但我不能，因为它在另一个类中。我的GUI和我的ActionListener类是分开的，但我想从另一个类访问JTextField，我有问题这样做。很抱歉，代码非常长，当我运行它时，它给了我nullpointer异常。我应该如何从BusinessLogic类访问JTextField？这是我的代码： BankApp课程：
import java.awt.CardLayout;
import static java.awt.Component.CENTER_ALIGNMENT;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class BankApp {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
BankGUI object1;
object1 = new BankGUI();
object1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
object1.setSize(600, 400);
object1.setLocationRelativeTo(null);
object1.setVisible(true);
}
});
}
}
BankGUI：
import java.awt.*;
import javax.swing.*;
import javax.swing.GroupLayout.Alignment;
public class BankGUI extends JFrame {
private static CardLayoutBankNavigationController controller;
public static JTextField NameField;
public BankGUI() {
super("Banking App");
CardLayout layout = new CardLayout();
setLayout(layout);
controller = new CardLayoutBankNavigationController(getContentPane(), layout);
add("Main Menu", createMainMenu());
add("Register", RegisterView("Register"));
add("Login", LoginView("Login"));
add("About", About("About"));
add("Exit", otherView("Exit"));
controller.setView("Main Menu");
}
public static JPanel About(String named) {
JPanel About= new JPanel(new GridBagLayout());
JTextArea AboutTextArea = new JTextArea(8,35);
JButton MainMenuButton = new JButton("Back");
GridBagConstraints gbc = new GridBagConstraints();
gbc.insets = new Insets(10,10,10,10);
gbc.anchor = GridBagConstraints.CENTER;
AboutTextArea.setWrapStyleWord(true);
AboutTextArea.setEditable(false);
AboutTextArea.setLineWrap(true);
AboutTextArea.setFont(new Font("Serif", Font.PLAIN, 22));
AboutTextArea.setText("This is a banking app made by Velizar Mitrev. "
+ "\nIts created only for learning purposes and its my first GUI application. "
+ "Its application that simulates online banking applications where you create account "
+ "and in the account you have your money. "
+ "\nHave Fun with it!");
gbc.gridx = 0;
gbc.gridy = 0;
About.add(AboutTextArea, gbc);
MainMenuButton.setFocusable(false);
MainMenuButton.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 1;
About.add(MainMenuButton, gbc);
////////////////
ButtonListener actionListener = new ButtonListener(controller, null);
MainMenuButton.addActionListener(actionListener);
return About;
}
///////////////////////////////////////////////////////
public static JPanel RegisterView(String named) {
JPanel Register = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.insets = new Insets(10,15,10,15);
gbc.anchor = GridBagConstraints.WEST;
JLabel Name;
JLabel Surname;
JTextField SurnameField;
JLabel Password;
JPasswordField PasswordField;
JLabel ConfirmPassword;
JPasswordField ConfirmPasswordField;
JLabel Email;
JTextField EmailField;
JButton RegisterButton;
JButton MainMenuButton;
Name= new JLabel("Name:");
Name.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 0;
gbc.weightx = 0;
gbc.weighty = 1;
Register.add((Name), gbc);
gbc.gridx = 1;
gbc.gridy = 0;
NameField = new JTextField(15);
NameField.setFont(new Font("Serif",Font.PLAIN,20));
Register.add(NameField, gbc);
Surname = new JLabel("Surname:");
Surname.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 1;
Register.add((Surname), gbc);
SurnameField = new JTextField(15);
SurnameField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 1;
Register.add(SurnameField, gbc);
Password = new JLabel("Password:");
Password.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 2;
Register.add((Password), gbc);
PasswordField = new JPasswordField(15);
PasswordField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 2;
Register.add(PasswordField, gbc);
ConfirmPassword = new JLabel("Confirm password:");
ConfirmPassword.setFont(new Font("Serif", Font.PLAIN, 22));
gbc.gridx = 0;
gbc.gridy = 3;
Register.add((ConfirmPassword), gbc);
ConfirmPasswordField = new JPasswordField(15);
ConfirmPasswordField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 3;
Register.add(ConfirmPasswordField, gbc);
Email = new JLabel("Email:");
Email.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 4;
Register.add((Email), gbc);
EmailField = new JTextField(15);
EmailField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 4;
Register.add(EmailField, gbc);
MainMenuButton = new JButton("Back");
MainMenuButton.setFont(new Font("Serif", Font.PLAIN, 24));
MainMenuButton.setPreferredSize(new Dimension(120, 40));
MainMenuButton.setFocusable(false);
gbc.gridx = 0;
gbc.gridy = 5;
Register.add((MainMenuButton), gbc);
RegisterButton = new JButton("Register");
RegisterButton.setFont(new Font("Serif", Font.PLAIN, 24));
RegisterButton.setPreferredSize(new Dimension(150, 40));
RegisterButton.setFocusable(false);
gbc.gridx = 1;
gbc.gridy = 5;
Register.add(RegisterButton, gbc);
////////////////
ButtonListener actionListener = new ButtonListener(controller, null);
MainMenuButton.addActionListener(actionListener);
RegisterButton.addActionListener(actionListener);
return Register;
}
public static JPanel LoginView(String named) {
JPanel Login= new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.insets = new Insets(10,15,20,15);
gbc.anchor = GridBagConstraints.NORTH;
JLabel Name;
JLabel Password;
JTextField NameField;
JPasswordField PasswordField;
JButton LoginButton;
JButton MainMenuButton;
Name = new JLabel("Name:");
Name.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 0;
Login.add(Name, gbc);
NameField = new JTextField(15);
NameField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 0;
Login.add(NameField, gbc);
Password = new JLabel("Password:");
Password.setFont(new Font("Serif", Font.PLAIN, 24));
gbc.gridx = 0;
gbc.gridy = 1;
Login.add(Password, gbc);
PasswordField = new JPasswordField(15);
PasswordField.setFont(new Font("Serif",Font.PLAIN,20));
gbc.gridx = 1;
gbc.gridy = 1;
Login.add(PasswordField, gbc);
MainMenuButton = new JButton("Back");
MainMenuButton.setFont(new Font("Serif", Font.PLAIN, 24));
MainMenuButton.setPreferredSize(new Dimension(120, 40));
MainMenuButton.setFocusable(false);
gbc.gridx = 0;
gbc.gridy = 2;
Login.add(MainMenuButton, gbc);
LoginButton = new JButton("Login");
LoginButton.setFont(new Font("Serif", Font.PLAIN, 24));
LoginButton.setPreferredSize(new Dimension(120, 40));
LoginButton.setFocusable(false);
gbc.gridx = 1;
gbc.gridy = 2;
Login.add(LoginButton, gbc);
ButtonListener actionListener = new ButtonListener(controller, null);
MainMenuButton.addActionListener(actionListener);
LoginButton.addActionListener(actionListener);
return Login;
}
////////////////////////////////////////////////////////
public static JPanel otherView(String named) {
JPanel view = new JPanel();
view.setLayout(new BoxLayout(view, BoxLayout.PAGE_AXIS));
JButton mainMenu = new JButton("Main Menu");
view.add(mainMenu);
ButtonListener actionListener = new ButtonListener(controller, null);
mainMenu.addActionListener(actionListener);
return view;
}
public static JPanel createMainMenu() {
JPanel menu = new JPanel();
menu.setLayout(new BoxLayout(menu, BoxLayout.PAGE_AXIS));
menu.add(Box.createRigidArea(new Dimension(0, 10)));
JLabel IntroText = new JLabel("Banking Application");
IntroText.setMaximumSize(new Dimension(280, 60));
IntroText.setFont(new Font("Serif", Font.PLAIN, 34));
IntroText.setAlignmentX(CENTER_ALIGNMENT);
menu.add(IntroText);
menu.add(Box.createRigidArea(new Dimension(0, 20)));
JButton CreateAccount = new JButton("Register");
CreateAccount.setMaximumSize(new Dimension(200, 50));
CreateAccount.setFont(new Font("Serif", Font.PLAIN, 24));
CreateAccount.setAlignmentX(CENTER_ALIGNMENT);
CreateAccount.setFocusable(false);
CreateAccount.setActionCommand("CreateAccount");
menu.add(CreateAccount);
menu.add(Box.createRigidArea(new Dimension(0, 20)));
JButton LoginAccount = new JButton("Login");
LoginAccount.setMaximumSize(new Dimension(200, 50));
LoginAccount.setFont(new Font("Serif", Font.PLAIN, 24));
LoginAccount.setAlignmentX(CENTER_ALIGNMENT);
LoginAccount.setFocusable(false);
LoginAccount.setActionCommand("LoginAccount");
menu.add(LoginAccount);
menu.add(Box.createRigidArea(new Dimension(0, 20)));
JButton AboutButton = new JButton("About");
AboutButton.setMaximumSize(new Dimension(200, 50));
AboutButton.setFont(new Font("Serif", Font.PLAIN, 24));
AboutButton.setAlignmentX(CENTER_ALIGNMENT);
AboutButton.setFocusable(false);
menu.add(AboutButton);
menu.add(Box.createRigidArea(new Dimension(0, 20)));
JButton ExitButton = new JButton("Exit");
ExitButton.setMaximumSize(new Dimension(200, 50));
ExitButton.setFont(new Font("Serif", Font.PLAIN, 24));
ExitButton.setAlignmentX(CENTER_ALIGNMENT);
ExitButton.setFocusable(false);
menu.add(ExitButton);
ButtonListener actionListener = new ButtonListener(controller, null);
CreateAccount.addActionListener(actionListener);
LoginAccount.addActionListener(actionListener);
AboutButton.addActionListener(actionListener);
ExitButton.addActionListener(actionListener);
return menu;
}
public JTextField getTextField() {
return NameField;
}
}
这是我的ActionListener类：
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ButtonListener implements ActionListener {
private BankNavigationController controller;
BankGUI gui;
BusinessLogic BL;
public ButtonListener(BankNavigationController controller, BankGUI gui) {
this.gui = gui;
this.controller = controller;
}
public void actionPerformed(ActionEvent e) {
if(e.getActionCommand() == "CreateAccount"){
controller.setView("Register");
}
if(e.getActionCommand() == "LoginAccount"){
controller.setView("Login");
}
if(e.getActionCommand() == "Back"){
controller.setView("Main Menu");
}
if(e.getActionCommand() == "About"){
controller.setView("About");
}
if(e.getActionCommand() == "Exit"){
System.exit(0);
}
if(e.getActionCommand() == "Exit"){
System.exit(0);
}
if(e.getActionCommand() == "Register")
{
BL.registerAccount(gui);
}
}
}
这是我的CardLayout：
import java.awt.*;
public class CardLayoutBankNavigationController implements
BankNavigationController {
private Container parent;
private CardLayout layout;
public CardLayoutBankNavigationController(Container parent, CardLayout layout) {
this.parent = parent;
this.layout = layout;
}
@Override
public void setView(String command) {
layout.show(parent, command);
}
}
这是BankNavigationInterface
public interface BankNavigationController {
public void setView(String command);
}
这是BusinessLogic类：
import java.util.HashMap;
import java.util.Map;
public class BusinessLogic {
Map<String, UserAccount> UserAccounts = new HashMap<String, UserAccount>();
public BusinessLogic(BankGUI gui){
}
public void registerAccount(BankGUI gui){
System.out.println(gui.getTextField());
}
}
我的问题是如何从BusinessLogic访问BankGUI中的JTextField？