//LoginDialogDemo.java import java.awt.*; import javax.swing.*; import java.awt.event.*;

public class LoginDialogDemo extends JFrame { JButton button = new JButton("Click Me"); JPanel panel = new JPanel(new FlowLayout());

public LoginDialogDemo() { final JFrame frame = this; this.getContentPane().add(panel,BorderLayout.SOUTH); panel.add(button); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { showLoginDialog(frame); } }); this.setSize(300,200); this.setTitle("显示登陆对话框"); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.show(); }

void showLoginDialog(JFrame frame){ JPanel p = new JPanel(new GridLayout(0,1)); JTextField tfUserName = new JTextField(); JPasswordField tfPassword = new JPasswordField(); p.add(new JLabel("Username: ")); p.add(tfUserName); p.add(new JLabel("Password: ")); p.add(tfPassword); if (JOptionPane.showConfirmDialog(frame // may want to pass your application frame here ,p ,"Login" ,JOptionPane.OK_CANCEL_OPTION ,JOptionPane.PLAIN_MESSAGE ) == JOptionPane.OK_OPTION) { System.out.println("User Name:"+tfUserName.getText()); System.out.println("Password:" + new String(tfPassword.getPassword())); } }

public static void main(String[] args) { LoginDialogDemo frame = new LoginDialogDemo(); } }

看看这里的this 是什么意思?