创建登录界面

import javax.swing.*; import java.awt.*; import java.awt.event.*;public class dljm extends JFrame implements ActionListener {      JPanel loginPan;      JButton btnLogin,btnExit;    JLabel lblUser,lblPassword,lblLogo;    Dimension dsSize;    Toolkit toolkit = Toolkit.getDefaultToolkit();    JTextField txtUser;    JPasswordField pwdPassword;    public dljm()      {        super("登陆界面");        loginPan=new JPanel();        this.getContentPane().add(loginPan);        lblUser=new JLabel("用户名：");        lblPassword=new JLabel("密码：");        txtUser=new JTextField(20);        pwdPassword =new JPasswordField(20);        btnLogin=new JButton("确定");        btnExit=new JButton("取消");        btnLogin.addActionListener(this);        btnExit.addActionListener(this);        Font fontstr=new Font("宋体",Font.PLAIN,13);          lblUser.setFont(fontstr);        txtUser.setFont(fontstr);        lblPassword.setFont(fontstr);        pwdPassword.setFont(fontstr);        btnLogin.setFont(fontstr);        lblUser.setForeground(Color.BLACK);        lblPassword.setForeground(Color.BLACK);        btnLogin.setBackground(Color.LIGHT_GRAY);        btnExit.setBackground(Color.LIGHT_GRAY);        loginPan.add(lblUser);        loginPan.add(txtUser);        loginPan.add(lblPassword);        loginPan.add(pwdPassword);        loginPan.add(btnLogin);        loginPan.add(btnExit);        loginPan.setLayout(null);          lblUser.setBounds(30,10,60,25);        lblPassword.setBounds(30,40,60,25);        txtUser.setBounds(80,10,150,35);        pwdPassword.setBounds(80,40,150,25);        btnLogin.setBounds(40,80,80,25);        btnExit.setBounds(140,80,80,35);        setResizable(false);        setSize(280,150);        setVisible(true);    }public void actionPerformed( ActionEvent ae){    if(ae.getSource() == btnLogin){        if((txtUser.getText().equals("user")) && (pwdPassword.equals("user")))            JOptionPane.showMessageDialog(null,"登陆成功!");        else            JOptionPane.showMessageDialog(null,"用户名 或者密码错误！");    }    if(ae.getSource() == btnExit)        System.exit(0);}    public static void main(String[] args) {        // TODO 自动生成的方法存根        dljm load = new dljm();    }}

知识要点:事件处理概述;
WindowEvent事件处理；
KeyEvent事件处理；
MouseEvent事件处理；
添加Swing,AWT和Event库；
定义构造方法‘
设置界面标题；
采用NULL布局；