java - Action 监听器错误

Question

当我实现 ActionListener 时，我不断收到错误消息。我真的不明白如何解决它。我执行了 actionPerformed (ActionEvent ev) {} 并放置登录按钮以使用 lg.addActionListener(this); 调用它；

import java.awt.*;
import javax.swing.*;
import java.awt.Event.*;
import java.applet.Applet;

public class LoginScreen extends JApplet implements ActionListener   {
    JTextField un;
    JPasswordField pw;
    JButton lg;
    JLabel user,pass;

    public LoginScreen () {
        un = new JTextField ();
        pw = new JPasswordField ();
        lg = new JButton ("login");
        user = new JLabel ("username");
        pass = new JLabel ("password");

        lg.addActionListener(this);

        this.setLayout(null);

        user.setBounds(10, 10, 120, 20);
        pass.setBounds(10, 30, 120, 20);
        un.setBounds(140, 10, 200, 20);
        pw.setBounds(140, 30, 200, 20);

        lg.setBounds(140, 55, 100, 20);

        this.add(user);
        this.add(pass);
        this.add(un);
        this.add(pw);
        this.add(lg);

        this.setSize(500, 300);
        this.setVisible(true);
        }       
    public void actionPerformed(ActionEvent ev) {

    }
}

Answer 1

将 import java.awt.Event.*; 更改为 import java.awt.event.*;

Java 区分大小写。

同时更改import java.applet.Applet; -> import javax.swing.JApplet;