java 的简单应用--设计一个简单的变色登录界面

package zuoye0517;import java.awt.*;import javax.swing.*;import java.awt.event.*;import javax.swing.JFrame;import javax.swing.JPanel;import javax.swing.JButton;import javax.swing.JLabel;import javax.swing.JMenu;import javax.swing.JMenuBar;import javax.swing.JMenuItem;import javax.swing.JTextField;import java.awt.Font;import java.awt.Color;import javax.swing.JPasswordField;import java.awt.event.ActionListener;import java.awt.event.ActionEvent;import javax.swing.JOptionPane;public class DENGLU extends JFrame{ public JPanel pnluser; public JLabel lbluserLogIn;public JLabel lbluserName; public JLabel lbluserPWD; public JTextField txtName; public JPasswordField pwdPwd;public JButton btnSub; public JButton btnReset; private JMenuBar mb;private JMenu col,ext;private JMenuItem gre,yel,blu,clo;public DENGLU(){ pnluser = new JPanel(); lbluserLogIn = new JLabel();  lbluserName = new JLabel(); lbluserPWD = new JLabel(); txtName = new JTextField();pwdPwd = new JPasswordField(); btnSub = new JButton();btnReset = new JButton();  userInit(); } public void userInit(){this.setSize(500,320);this.setTitle("简易变色登陆界面");mb=new JMenuBar();col=new JMenu("颜色选择");ext=new JMenu("退出");gre=new JMenuItem("绿色");yel=new JMenuItem("黄色");blu=new JMenuItem("蓝色");clo=new JMenuItem("退出系统");gre.addActionListener(new Handler1());yel.addActionListener(new Handler1());blu.addActionListener(new Handler1());clo.addActionListener(new Handler1());mb.add(col);mb.add(ext);col.add(gre);col.add(yel);col.add(blu);ext.add(clo);setJMenuBar(mb);this.pnluser.setLayout(null);this.pnluser.setBackground(null);this.lbluserLogIn.setText("用户登录");this.lbluserLogIn.setFont(new Font("宋体",Font.BOLD | Font.ITALIC,14));this.lbluserLogIn.setForeground(Color.RED);this.lbluserName.setText("用户名:"); this.lbluserPWD.setText("密    码:"); this.btnSub.setText("登录"); this.btnReset.setText("重置"); this.lbluserLogIn.setBounds(120,15,60,20); this.lbluserName.setBounds(50,55,60,20); this.lbluserPWD.setBounds(50,85,60,25);     this.txtName.setBounds(110,55,120,20);  this.pwdPwd.setBounds(110,85,120,20); this.btnSub.setBounds(85,120,60,20);this.btnSub.addActionListener(new ActionListener(){    public void actionPerformed(ActionEvent e){ btnsub_ActionEvent(e);    }       }  ); this.btnReset.setBounds(155,120,60,20);  this.pnluser.add(lbluserLogIn); this.pnluser.add(lbluserName); this.pnluser.add(lbluserPWD); this.pnluser.add(txtName); this.pnluser.add(pwdPwd);  this.pnluser.add(btnSub);  this.pnluser.add(btnReset);  this.add(pnluser);this.setVisible(true);}  public void btnsub_ActionEvent(ActionEvent e){String name = txtName.getText();String pwd = String.valueOf(pwdPwd.getPassword());if(name.equals("")){ JOptionPane.showMessageDialog(null,"账号不能为空","错误",JOptionPane.ERROR_MESSAGE); return;  }else if (pwd.equals("")){   JOptionPane.showMessageDialog(null,"密码不能为空","错误",JOptionPane.ERROR_MESSAGE);  return; }else if(true){ this.dispose(); }else{ JOptionPane.showMessageDialog(null,"账号或密码错误","错误",JOptionPane.ERROR_MESSAGE);return; }}   public class Handler1 implements ActionListener{public void actionPerformed(ActionEvent e){JMenuItem mi=(JMenuItem) e.getSource();if(mi==gre)  pnluser.setBackground(Color.green);if(mi==yel)  pnluser.setBackground(Color.yellow);if(mi==blu)  pnluser.setBackground(Color.blue);if(mi==clo)  System.exit(0);} }public void btnreset_ActionEvent(ActionEvent e){txtName.setText(""); pwdPwd.setText("");} public static void main(String[] args){  new DENGLU();} }

将两个单独的程序写成一个程序，可能麻烦一点  不过简单易懂。首先是编辑选项栏，定义变量，然后是一个简单登录界面的编写， 需要注意的是对部分区域的监听