【java】事件监听——通过点击不同的按钮，让面板的背景色发生相应的变化

/* * 作者：筱筱 * 功能：通过点击不同的按钮，让面板的背景色发生相应的变化 */import java.awt.*;import java.awt.event.*;import javax.swing.*;public class Fourbutton extends JFrame implements ActionListener{    JPanel jp = null;    JButton jb1 = null;    JButton jb2 = null;    JButton jb3 = null;    JButton jb4 = null;    public static void main(String[] args) {        Fourbutton tb = new Fourbutton();    }    //构造器    public Fourbutton(){        jp = new JPanel();        jb1 = new JButton("Black");             jb2 = new JButton("Red");        jb3 = new JButton("Blue");        jb4 = new JButton("Yellow");        this.add(jp);        this.add(jb1,BorderLayout.NORTH);        this.add(jb2, BorderLayout.SOUTH);        this.add(jb3,BorderLayout.WEST);            this.add(jb4,BorderLayout.EAST);                    //注册监听        jb1.addActionListener(this);        jb1.setActionCommand("Black");        jb2.addActionListener(this);        jb2.setActionCommand("Red");        jb3.addActionListener(this);        jb3.setActionCommand("Blue");        jb4.addActionListener(this);        jb4.setActionCommand("Yellow");        this.setTitle("点击按钮");        this.setSize(300, 200);        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        this.setVisible(true);    }    //对事件处理的方法    public void actionPerformed(ActionEvent e) {        // TODO Auto-generated method stub        if(e.getActionCommand().equals("Black")){            System.out.println("你点击的黑色按钮");            jp.setBackground(Color.BLACK);          }else if(e.getActionCommand().equals("Red")){            System.out.println("你点击的红色按钮");            jp.setBackground(Color.RED);        }else if(e.getActionCommand().equals("Blue")){            System.out.println("你点击的蓝色按钮");            jp.setBackground(Color.BLUE);        }else if(e.getActionCommand().equals("Yellow")){            System.out.println("你点击的黄色按钮");            jp.setBackground(Color.YELLOW);        }else{            System.out.println("不知道");        }    }}

程序结果：