下拉菜单、右键菜单、底部按钮实现背景颜色的改变_jpopupmenu设置选中的背景样式-优快云博客

本文介绍了一个使用Java Swing实现的示例程序，通过按钮和弹出菜单选择不同颜色来改变面板背景色。程序包括JPopupMenu和JMenu的使用，以及鼠标事件监听。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class TestJPopupMenu extends JFrame implements ActionListener,MouseListener{
     JMenuBar jmb;
     JMenu ColorMenu;
     JPopupMenu pop;
     JButton b1,b2,b3,b4;
     JMenuItem j1,j2,j3,j4;
     Container cp=null;
     JPanel p1,p2;
     public TestJPopupMenu(){
           super("改变背景颜色");
           jmb=new JMenuBar();
           setJMenuBar(jmb);
           ColorMenu=new JMenu("Color");
           jmb.add(ColorMenu);
           j1=new JMenuItem("red");
           j2=new JMenuItem("green");
           j3=new JMenuItem("blue");
           j4=new JMenuItem("gray");
           ColorMenu.add(j1);
           ColorMenu.add(j2);
           ColorMenu.add(j3);
           ColorMenu.add(j4);
           pop=new JPopupMenu();
           JMenuItem i1=new JMenuItem("red");
           JMenuItem i2=new JMenuItem("green");
           JMenuItem i3=new JMenuItem("blue");
           JMenuItem i4=new JMenuItem("gray");
            ColorMenu.add(j1);ColorMenu.addSeparator();
            ColorMenu.add(j2);ColorMenu.addSeparator();
            ColorMenu.add(j3);ColorMenu.addSeparator();
            ColorMenu.add(j4);
            pop.add(i1);   pop.add(i2); pop.add(i3);   pop.add(i4);
            i1.addActionListener(this);
            i2.addActionListener(this);
            i3.addActionListener(this);
            i4.addActionListener(this);
            b1=new JButton("red");
            b2=new JButton("green");
            b3=new JButton("blue");
            b4=new JButton("gray");
            p1=new JPanel();p1 . setBackground(Color.CYAN);
            p2=new JPanel();
            p2.setLayout(new FlowLayout(FlowLayout.CENTER,20,10));
            cp=getContentPane();
            p2.add(b1);p2.add(b2);p2.add(b3);p2.add(b4);
            cp.add(p1,BorderLayout.CENTER);
            cp.add(p2,BorderLayout.SOUTH);
            b1.addActionListener(this);
            b2.addActionListener(this);
            b3.addActionListener(this);
            b4.addActionListener(this);
            j1.addActionListener(this);
            j2.addActionListener(this);
            j3.addActionListener(this);
            j4.addActionListener(this);
            cp.addMouseListener(this);
            setSize(200,300);
            setVisible(true);
    }
     public void actionPerformed(ActionEvent e){
           if(e.getSource()==b1)
              p1.setBackground(Color.red);
           if(e.getSource()==b2)
              p1.setBackground(Color.green);
           if(e.getSource()==b3)
              p1.setBackground(Color.blue);
           if(e.getSource()==b4)
              p1.setBackground(Color.gray);
           String m=e.getActionCommand();
    if(m=="red")
    p1.setBackground(Color.red);
    if(m=="green")
    p1.setBackground(Color.green);
    if(m=="blue")
    p1.setBackground(Color.blue);
    if(m=="gray")
    p1.setBackground(Color.gray);
           }
    public void mouseReleased(MouseEvent e){
        if (e.isPopupTrigger())
            pop.show((Component)e.getSource(),e.getX(),e.getY());
    }
    public void mousePressed(MouseEvent e){}
    public void mouseEntered(MouseEvent e){}
    public void mouseClicked(MouseEvent e){}
    public void mouseExited(MouseEvent e){}
    public static void main(String args[]){
              TestJPopupMenu frame = new TestJPopupMenu ();
              frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
              frame.setSize(400,400);
               frame.setVisible(true);
    }

}