login.java

主要是对于JAVA的编程的基本语言 希望能够帮得上你。

package awt;

import java.awt.*;
import java.awt.event.*;

public class Login extends Frame implements ActionListener{
	
	//声明部分
	Label lblUserName,lblPassword;
	TextField txtUserName,txtPassword;
	Button btnOK,btnCancel;	
	Panel panTop,panMiddle, panBottom;
	String strUserName, strPassword;
	Frame frmMain;
	Image imgBack;
	MainCanvas m_MainCanvas;
	
	//构造方法
	public Login(String title){
		super(title);
		initialize();
	}
	
	private void initialize(){
		//创建对象
		frmMain=new Frame("成绩管理系统V1.0");
		lblUserName=new Label("输入用户名：");
		lblPassword=new Label("请输入密码：");
		txtUserName=new TextField("",20);
		txtPassword=new TextField("",20);
		btnOK=new Button("确定");
		btnCancel=new Button("取消");
		panTop=new Panel();
		panMiddle=new Panel();
		panBottom=new Panel();
		imgBack=Toolkit.getDefaultToolkit().createImage("awt/Azul.jpg");
		m_MainCanvas=new MainCanvas();
		
		//添加组件
		panTop.add(lblUserName);
		panTop.add(txtUserName);
		panMiddle.add(lblPassword);
		panMiddle.add(txtPassword);
		panBottom.add(btnOK);
		panBottom.add(btnCancel);
		this.add(panTop);
		this.add(panMiddle);
		this.add(panBottom);	
		frmMain.add(m_MainCanvas);
		
		//设置属性		
		this.setLayout(new GridLayout(3,1));		
		//this.setSize(250, 200); //设置窗口大小
		this.setSize(new Dimension(250,200)); //设置窗口大小
		/*		 
		 this.setLocation((int)(Toolkit.getDefaultToolkit().getScreenSize().getWidth()-this.getWidth())/2,
				(int)(Toolkit.getDefaultToolkit().getScreenSize().getHeight()-this.getHeight())/2); //让窗口居中
		 */		
		this.setLocationRelativeTo(null);//让窗口居中
		this.setResizable(false);	//窗口不可调整大小		
		this.pack(); //使窗口恰好容纳组件
		this.setVisible(true);	// 让窗口可见
		txtPassword.setEchoChar('*');  //设置回显字符
		frmMain.setSize((int)Toolkit.getDefaultToolkit().getScreenSize().getWidth(),
				(int)Toolkit.getDefaultToolkit().getScreenSize().getHeight());
		
		//注册监听器，编写事件处理代码
		this.addWindowListener(new WindowAdapter(){
			@Override
			public void windowClosing(WindowEvent e) {				
				System.exit(0);
			}
		});
		
		frmMain.addWindowListener(new WindowAdapter(){
			@Override
			public void windowClosing(WindowEvent e) {				
				System.exit(0);
			}
		});
		
		btnOK.addActionListener(this);
		btnCancel.addActionListener(this);
	}	
	
	public static void main(String[] args) {
		new Login("登录");
	}

	//单击按钮事件处理代码
	public void actionPerformed(ActionEvent e) {
		strUserName=txtUserName.getText().trim();
		strPassword=txtPassword.getText().trim();
		if(e.getSource()==btnOK){
			if(strUserName.equals("admin")){
				if(strPassword.equals("12345")){
					System.out.println("欢迎使用本系统！");
					this.setVisible(false);
					frmMain.setVisible(true);
				}else{
					System.out.println("密码错误，请重新输入。");
					txtPassword.requestFocus();
					txtPassword.setText("");
				}				
			}else{
				System.out.println("用户名不存在，请重新输入。");
				txtUserName.requestFocus();
				txtUserName.setSelectionStart(0);
				txtUserName.setSelectionEnd(txtUserName.getText().length());
			}
		}else if(e.getSource()==btnCancel){
			System.exit(0);
		}			
	}	
	
	//定义内部类——自定义画布类
	class MainCanvas extends Canvas{
		public void paint(Graphics g){
			g.drawImage(imgBack,0,0,frmMain.getWidth(),frmMain.getHeight(),this);
		}
	}
}