如何用java图形化界面实现一个登录窗口

登录窗口一般很常见，现在让我们自己也来写一个吧！

PS：很多import是重复的，是因为我是分了几个类写的，必须单独导入

//模拟qq登录窗口import java.awt.*;import java.io.*;import java.awt.event.*;import javax.swing.*;public class QQGUI extends JFrame implements ActionListener{    private JLabel userLa;    private JLabel pwdLa;    private JLabel verCodeLa;//验证码    private JTextField userTxt;    private JPasswordField pwdTxt;    private JTextField verCodeTxt;//验证码    private JButton sureBt;    private JButton quitBt;    private Mypanel mp;    //构造方法    public QQGUI()    {        Init();    }    public void Init()    {        Frame frame = new Frame("QQ登录");        //创建出控件对象（因为上面只是声明出来，并没有给出实际的空间)        //用户文本        userLa = new JLabel();        userLa.setText("用户名：");        userLa.setSize(60, 50);        userLa.setLocation(100, 80);        //密码文本        pwdLa = new JLabel();        pwdLa.setText("密码：");        pwdLa.setSize(50, 50);        pwdLa.setLocation(100, 120);        //用户输入框        userTxt = new JTextField();        userTxt.setSize(100, 20);        //this.setSize(width, height)        userTxt.setLocation(170, 95);        //密码输入框        pwdTxt = new JPasswordField();        pwdTxt.setSize(100, 20);        pwdTxt.setLocation(170, 135);        //确认按钮        sureBt = new JButton("登录");        sureBt.setSize(60, 25);        sureBt.setLocation(135, 260);        //退出按钮        quitBt = new JButton("退出");        quitBt.setSize(60, 25);        quitBt.setLocation(240, 260);        //验证码文本        verCodeLa = new JLabel();        verCodeLa.setText("验证码：");        verCodeLa.setSize(60, 50);        verCodeLa.setLocation(100,165);        //验证码文本框        verCodeTxt = new JTextField();        verCodeTxt.setSize(100, 20);        verCodeTxt.setLocation(170, 180);        //验证码        mp = new Mypanel();        mp.setSize(100, 30);        mp.setLocation(280, 175);        //登录方式选择框        JComboBox xlk=new JComboBox();        xlk.setSize(60, 20);        xlk.setLocation(250, 220);        xlk.addItem("在线");        xlk.addItem("隐身");        xlk.addItem("离开");        this.setLayout(null);        this.setSize(500, 400);        this.add(userLa);        this.add(pwdLa);        this.add(userTxt);        this.add(pwdTxt);        this.add(sureBt);        this.add(quitBt);        this.add(verCodeLa);        this.add(verCodeTxt);        this.add(mp);        this.add(xlk);        sureBt.addActionListener(this);        quitBt.addActionListener(this);        this.setVisible(true);    }    //具体事件的处理     public void actionPerformed(ActionEvent e)     {         //获取产生事件的事件源强制转换         JButton bt = (JButton)e.getSource();         //获取按钮上显示的文本         String str = bt.getText();         if(str.equals("登录"))         {             if(!CheckIsNull())             {                 //获取用户所输入的用户名                 String user = userTxt.getText().trim();                 //获取用户所输入的密码                 String pwd = pwdTxt.getText().trim();                 if(checkUserAndPwd(user,pwd))                 {                     //隐藏当前登录窗口                     this.setVisible(false);                     //验证成功创建一个主窗口                     MainFrame frame = new MainFrame();                 }                 else                 {                     //如果错误则弹出一个显示框                     JOptionPane pane = new JOptionPane("用户或密码错误");                     JDialog dialog  = pane.createDialog(this,"警告");                     dialog.show();                 }             }         }         else         {             //调用系统类中的一个正常退出             System.exit(0);         }     }     private boolean CheckIsNull()     {         boolean flag = false;         if(userTxt.getText().trim().equals(" "))         {             flag = true;         }         else         {             if(pwdTxt.getText().trim().equals(" "))             {                 flag = true;             }         }         return flag;     }     private boolean checkUserAndPwd(String user,String pwd)     {         boolean result = false;         try         {             FileReader  file = new FileReader("D:\\Workspaces\\MyEclipse 8.5\\testGUI.txt");              BufferedReader bre =  new BufferedReader(file);             String str = bre.readLine();            while(str!=null)            {                 String[] strs = str.split(",");                 if(strs[0].equals(user))                 {                     if(strs[1].equals(pwd))                     result = true;                 }                 str = bre.readLine();            }            file.close();         }catch(Exception ex)         {             System.out.print("");         }         return result;     }}//MainFrame类import javax.swing.*;public class MainFrame extends JFrame {    public MainFrame()    {        this.setSize(300, 300);        this.setVisible(true);    }}//验证码的生成import java.awt.*;import java.util.*;public class Mypanel extends Panel {    public void paint(Graphics g)    {        int height = 50;        int width = 90;        //验证码框背景颜色        g.setColor(Color.LIGHT_GRAY);        //填充验证码背景        g.fillRect(0, 0, width, height);        g.setColor(Color.BLACK);        g.drawRect(0, 0, width-1, height-1);        Random r = new Random();        //设置干扰点        for(int i = 0;i<100;i++)        {            int x = r.nextInt(width)-1;            int y = r.nextInt(height)-1;            g.drawOval(x, y, 2, 2);        }        g.setFont(new Font("黑体",Font.BOLD,20));//设置验证码字体以及大小        g.setColor(Color.RED);//设置验证码字体颜色        //生成随机验证码        char[] tmp = ("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();        StringBuilder sb = new StringBuilder();        for(int i = 0;i<4;i++)        {            int pos = r.nextInt(tmp.length);            char c = tmp[pos];            sb.append(c + " ");        }        g.drawString(sb.toString(), 10, 15);//写入验证码    }}//下拉框的实现import java.awt.*;import java.awt.event.*;import javax.swing.*;public class xialakuang extends JFrame {    private JComboBox comboBox;//定义一个组合框    public void xia ()    {        //JPanel panel = new JPanel();//创建一个JPanel面板        comboBox = new JComboBox();        comboBox.addItem("在线");        comboBox.addItem("隐身");        comboBox.addItem("离开");        this.add(comboBox);        //this.add(panel);        this.setSize(200, 100);        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        this.setVisible(true);    }}//测试public class testQQGUI {    /**     * @param args     */    public static void main(String[] args) {        // TODO Auto-generated method stub        QQGUI frame = new QQGUI();    }}