使用JFrame创建登录窗口(可参考下图或自行设计布局) 当点击登录按钮时,对输入的用户名为和密码进行验证:  当输入的用户为admin,密码为1234时,弹出消息对话框,提示信息为:“用户名和密码正确”,否则,提

示错误消息对话框,提示信息为:“用户名或密码错误”。以下是 Java 代码实现：

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

public class LoginFrame extends JFrame implements ActionListener {
    private JTextField usernameField;
    private JPasswordField passwordField;
    private JButton loginButton;
    
    public LoginFrame() {
        setTitle("Login");
        setSize(300, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setLayout(new GridLayout(3, 2));

        JLabel usernameLabel = new JLabel("Username:");
        panel.add(usernameLabel);
        usernameField = new JTextField();
        panel.add(usernameField);

        JLabel passwordLabel = new JLabel("Password:");
        panel.add(passwordLabel);
        passwordField = new JPasswordField();
        panel.add(passwordField);

        loginButton = new JButton("Login");
        loginButton.addActionListener(this);
        panel.add(loginButton);

        add(panel);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        String username = usernameField.getText();
        String password = new String(passwordField.getPassword());
        if (username.equals("admin") && password.equals("1234")) {
            JOptionPane.showMessageDialog(this, "Username and password are correct.");
        } else {
            JOptionPane.showMessageDialog(this, "Username or password is incorrect.");
        }
    }

    public static void main(String[] args) {
        LoginFrame loginFrame = new LoginFrame();
    }
}

这段代码创建了一个登录窗口，包含用户名输入框、密码输入框和登录按钮。当用户点击登录按钮时，程序会读取输入框中的用户名和密码，并判断是否正确。如果用户名为 "admin" 且密码为 "1234"，则弹出提示框显示"Username and password are correct."，否则弹出提示框显示"Username or password is incorrect."。