mouseClicked事件的异常

Question

该程序在将凭据传递给另一个类时调用它。问题是，在调用另一个类的JFrame（setVisible = 1）时，线程中发生了异常。

程序：

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Login window = new Login();
                    window.frmLogin.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }




    /**
     * Create the application.
     */
    public Login() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    public void initialize() {
        frmLogin = new JFrame();
        frmLogin.setTitle("Login");
        frmLogin.setSize(500,300);
        frmLogin.setResizable(false);
        frmLogin.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmLogin.getContentPane().setLayout(null);

        user = new JTextField();
        user.setBounds(204, 90, 86, 20);
        frmLogin.getContentPane().add(user);
        user.setColumns(10);

        JLabel lblUsername = new JLabel("Username:");
        lblUsername.setBounds(113, 90, 81, 20);
        frmLogin.getContentPane().add(lblUsername);

        JLabel lblPassword = new JLabel("Password:");
        lblPassword.setBounds(113, 138, 81, 20);
        frmLogin.getContentPane().add(lblPassword);

        login = new JButton("Login");

        login.addMouseListener(new MouseAdapter() {
            @Override




            public void mouseClicked(MouseEvent arg0) {
                String b = new String(pass.getPassword());

                AdDAuthenticator adAuthenticator = new AdDAuthenticator();
                Map<String,Object> attrs = adAuthenticator.authenticate(user.getText(), b);

                if (attrs != null) {
                    for (String attrKey : attrs.keySet()) {
                        if (attrs.get(attrKey) instanceof String) {
                            System.out.println(attrKey +": "+attrs.get(attrKey));
                        } else {
                            System.out.println(attrKey +": (Multiple Values)");
                            for (Object o : (HashSet<?>)attrs.get(attrKey)) {
                                System.out.println("\t value: " +o);
                            }
                        }
                    }
                    updateScreen upd = new updateScreen();
                    frmLogin.dispose();   
                    upd.frm.setVisible(true);  //exception gets called.
                } else {
                    System.out.println("Attributes are null!");
                    System.out.println(b);
                    System.out.println(user.getText());
                    JOptionPane.showMessageDialog(null, "Credentials are Incorrect", "Error" , JOptionPane.WARNING_MESSAGE);
                    System.exit(0);
                }

            }
        });
        login.setBounds(165, 195, 89, 23);
        frmLogin.getContentPane().add(login);

        pass = new JPasswordField();
        pass.setBounds(204, 138, 86, 20);
        frmLogin.getContentPane().add(pass);

        lbljmawirelesscom = new JLabel("@.com");
        lbljmawirelesscom.setBounds(300, 92, 110, 17);
        frmLogin.getContentPane().add(#####);

    }







} 

例外情况如下：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Login$2.mouseClicked(Login.java:104)
at java.awt.AWTEventMulticaster.mouseClicked(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$500(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我不确定为什么会发生这种情况，也不确定如何处理异常。让我知道您是否需要更多信息。