如何返回到我的登錄屏幕？

Question

我的程序是使用Eclipse編寫的Java程序，我的程序首先必須將您的用戶名和密碼登錄到服務器，一旦驗證完畢，然後轉到一個新頁面（框架），在該頁面中有一個JMenuBar， JMenu和JMenuItem。我正在使用的JMenuItem在JMenu Exit下稱爲「註銷」，當您點擊註銷時，它將關閉屏幕。我想要發生的事情是將我重定向回登錄頁面。我嘗試了很多功能，但都沒有工作。我將不勝感激。

這裏是我的程序：

public class ScanTest2 extends JFrame { 

/** 
* 
*/ 
private static final long serialVersionUID = 1L; 
private static LoginDialog loginDialog; 

public ScanTest2() { 
    loginDialog = new LoginDialog(this, true); 
    loginDialog.setVisible(true); 
} 

public static void main(String[] args) 
{ 
    SwingUtilities.invokeLater(new Runnable() 
    { 

     public void run() 
     { 
      // create new frame for new page 
      JFrame frame = new ScanTest2(); 

      //create a Menu bar 
      JMenuBar menuBar = new JMenuBar(); 

      frame.getContentPane().setBackground(Color.BLUE); 
      try { 
       frame.setContentPane(new JLabel(new ImageIcon(ImageIO.read(new File("/home/a002384/logo2.bmp"))))); 

      } catch (IOException e) { 

       e.printStackTrace(); 
      } 
      frame.setTitle("Scan Gun Information"); 
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
      frame.setLocationRelativeTo(null); 
      frame.setExtendedState(JFrame.MAXIMIZED_BOTH); 

      // create Menus 
      JMenu databaseMenu = new JMenu("Database"); 
      JMenu ticketMenu = new JMenu("Tickets"); 
      JMenu inquiriesMenu = new JMenu("Inquiries"); 
      JMenu reportsMenu = new JMenu("Reports"); 
      JMenu exitMenu = new JMenu("Exit"); 

      // create Menu Items 
      JMenuItem lotMenuItem = new JMenuItem("Lots"); 
       lotMenuItem.setMnemonic(KeyEvent.VK_L); 
       lotMenuItem.setActionCommand("Lots"); 
      JMenuItem gunMenuItem = new JMenuItem("Guns"); 
       gunMenuItem.setMnemonic(KeyEvent.VK_G); 
       gunMenuItem.setActionCommand("Guns"); 
      JMenuItem batteryMenuItem = new JMenuItem("Batteries"); 
       batteryMenuItem.setMnemonic(KeyEvent.VK_B); 
       batteryMenuItem.setActionCommand("Batteries"); 
      JMenuItem logoutMenuItem = new JMenuItem("Logout"); 
       logoutMenuItem.setMnemonic(KeyEvent.VK_L); 
       logoutMenuItem.setActionCommand("Logout"); 


      MenuItemListener menuItemListener = new MenuItemListener(); 
      lotMenuItem.addActionListener(menuItemListener); 
      gunMenuItem.addActionListener(menuItemListener); 
      batteryMenuItem.addActionListener(menuItemListener); 
      logoutMenuItem.addActionListener(menuItemListener); 

      // add Menu Items to Menus 
      databaseMenu.add(lotMenuItem); 
      databaseMenu.add(gunMenuItem); 
      databaseMenu.add(batteryMenuItem); 
      exitMenu.add(logoutMenuItem); 

      // add menu to MenuBar 
      menuBar.add(databaseMenu); 
      menuBar.add(ticketMenu); 
      menuBar.add(inquiriesMenu); 
      menuBar.add(reportsMenu); 
      menuBar.add(exitMenu); 

      frame.setJMenuBar(menuBar); 
      frame.setVisible(true); 

     } // end of run method 

     class MenuItemListener implements ActionListener { 

      public void actionPerformed(ActionEvent e) { 
       String command = e.getActionCommand(); 
       if (command.equals("Logout")) 
        System.exit(0); 
        // go back to login screen 

      } 
     } 
    }); // end of Runnable 
}// end of Main 
} 

class LoginDialog extends JDialog { 

/** 
* 
*/ 
private static final long serialVersionUID = 1L; 

private final JLabel loginlbl = new JLabel("Username"); 
private final JLabel Passwordlbl = new JLabel("Password"); 

private final JTextField loginName = new JTextField(15); 
private final JPasswordField loginPassword = new JPasswordField(); 

private final JButton loginButton = new JButton("Login"); 
private final JButton cancelButton = new JButton("Cancel"); 

private final JLabel Status = new JLabel(" "); 

private String username; 
private String password; 

private int m_errCounter = 0; 

public static final int MAX_LOGIN_ATTEMPTS = 3; 

public LoginDialog() { 
    this(null, true); 
} 

public LoginDialog(final JFrame parent, boolean modal) { 
    super(parent, modal); 

    JPanel p3 = new JPanel(new GridLayout(2, 1)); 
    p3.add(loginlbl); 
    p3.add(Passwordlbl); 

    JPanel p4 = new JPanel(new GridLayout(2, 1)); 
    p4.add(loginName); 
    p4.add(loginPassword); 

    JPanel p1 = new JPanel(); 
    p1.add(p3); 
    p1.add(p4); 

    JPanel p2 = new JPanel(); 
    p2.add(loginButton); 
    p2.add(cancelButton); 

    JPanel p5 = new JPanel(new BorderLayout()); 
    p5.add(p2, BorderLayout.CENTER); 
    p5.add(Status, BorderLayout.NORTH); 
    Status.setForeground(Color.RED); 
    Status.setHorizontalAlignment(SwingConstants.CENTER); 

    setLayout(new BorderLayout()); 
    add(p1, BorderLayout.CENTER); 
    add(p5, BorderLayout.SOUTH); 
    pack(); 
    setLocationRelativeTo(null); 
    setDefaultCloseOperation(DISPOSE_ON_CLOSE); 

    loginPassword.enableInputMethods(true); 

    addWindowListener(new WindowAdapter() { 

     public void windowClosing(WindowEvent e) { 
      System.exit(0); 
     } 
    }); 

    loginButton.addActionListener(new ActionListener() { 

     public void actionPerformed(ActionEvent e) { 

      UniJava uJava = new UniJava(); 
      try { 
        username = loginName.getText(); 
        password = new String (loginPassword.getPassword()); 
        if (username == " " && password == " ") 
        { 
         Status.setText("Invalid username or password!"); 
        } 
        else 
        { 
         UniSession session = uJava.openSession(); 
         session.setHostName("docdbtst.starcalif.com"); 
         session.setUserName(username); 
         session.setPassword(password); 
         session.setAccountPath("/mnt/data1/DD"); 
         session.connect(); 
         parent.setVisible(true); 
         setVisible(false); 
        } 

      } catch (UniSessionException e1) { 

       if (++m_errCounter > MAX_LOGIN_ATTEMPTS) 
       { 
        JOptionPane.showMessageDialog(LoginDialog.this, 
          "All Login attempts failed!", 
          "Error", JOptionPane.ERROR_MESSAGE); 
        System.exit(1); 
       } 
       else 
       { 
        Status.setText("Invalid Login! Cannot Connect!"); 
        loginName.setText(""); 
        loginPassword.setText(""); 
       } 

       e1.printStackTrace(); 
      } 

     } 
    }); 
    cancelButton.addActionListener(new ActionListener() { 

     public void actionPerformed(ActionEvent e) { 
      setVisible(false); 
      parent.dispose(); 
      System.exit(0); 
     } 
    }); 
    } 
} 

Answer 1

System.exit()一切都將被清理 JFrame.dispose() vs System.exit()

logoutItem.addActionListener(new ActionListener() { 
     public void actionPerformed(ActionEvent arg0) { 
      f.dispose(); 
      // northInformation.removeAll(); 
      // init(); 
      LoginWindow login = new LoginWindow(); 
     } 
    });