loginsystem.java

一个简单的学生信息查询系统

//LoginSystem.java 


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

public class LoginSystem extends JFrame implements ActionListener { 
    private JLabel label_u; 

    private JLabel label_p; 

    private JButton button_ok; 

    private JButton button_cancel; 

    private JPasswordField passwordField; 

    private JTextField textField; 

    private Container con; 
 
    // 产生登录界面 
    public LoginSystem() { 
        super("登录界面"); 
        setSize(214, 143); 
        // setAlwaysOnTop(true); 
        con = getContentPane(); 
        con.setBackground(new Color(129, 249, 252)); 
        con.setLayout(null); 
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

        label_u = new JLabel(); 
        label_u.setFont(new Font("", Font.PLAIN, 14)); 
        label_u.setText("用户名"); 
        label_u.setBounds(10, 10, 60, 20); 
        con.add(label_u); 

        label_p = new JLabel(); 
        label_p.setFont(new Font("", Font.PLAIN, 14)); 
        label_p.setText("密码"); 
        label_p.setBounds(10, 46, 60, 20); 
        con.add(label_p); 

        textField = new JTextField(); 
        textField.setBounds(76, 10, 120, 20); 
        con.add(textField); 

        passwordField = new JPasswordField(); 
        passwordField.setBounds(76, 46, 120, 20); 
        passwordField.setEchoChar('*'); 
        con.add(passwordField); 

        button_ok = new JButton(); 
        button_ok.setText("确定"); 
        button_ok.setBounds(29, 77, 60, 23); 
        con.add(button_ok); 

        button_cancel = new JButton(); 
        button_cancel.setText("取消"); 
        button_cancel.setBounds(119, 77, 60, 23); 
        con.add(button_cancel); 

        passwordField.addActionListener(this); 
        button_ok.addActionListener(this); 

        button_cancel.addActionListener(this); 

        // 将窗口置于屏幕中央 
        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); 
        Dimension frameSize = this.getSize(); 
        if (frameSize.height > screenSize.height) { 
            frameSize.height = screenSize.height; 
        } 
        if (frameSize.width > screenSize.width) { 
            frameSize.width = screenSize.width; 
        } 
        setLocation((screenSize.width - frameSize.width) / 2, 
        (screenSize.height - frameSize.height) / 2); 
        setResizable(false); 
        setVisible(true); 
    } 

    public void actionPerformed(ActionEvent e) { 
        if (e.getSource() == button_ok || e.getSource() == passwordField) { 
            // 取得用户输入的用户名 
            String tempUser = textField.getText(); 
            // 取得用户输入的密码 
            char temp[] = passwordField.getPassword(); 
            String tempPass = new String(temp); 
            CheckUser checkUser = new CheckUser(); 
        if (checkUser.isValidUser(tempUser, tempPass) == false) { 
            passwordField.setText(""); 
            // 弹出警告对话框 
            JOptionPane.showMessageDialog(null, "用户名或密码不正确", "错误", 
            JOptionPane.ERROR_MESSAGE); 
        } else { 
   
            // 初始化主界面 
            setVisible(false); 
            int flag = checkUser.getUserType(tempUser); 
            new MainFrame(tempUser, flag); 
        } 
        } else if (e.getSource() == button_cancel) {
 
            System.exit(0); 
        } 
    } 
}