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

//左鍵彈出菜單

public class JPopMenuDemo extends JFrame {
   JRadioButtonMenuItem items[]; //菜單項
   Color[] colors={Color.blue,Color.pink,Color.yellow,Color.red,Color.orange}; //顏色數組
   JPopupMenu popupMenu; //彈出菜單

   public JPopMenuDemo()
   {
      super( "右鍵彈出菜單" ); //調用父類構造函數

      ChangeColorAction action = new ChangeColorAction(); //菜單項事件處理
      String[] str = {"Blue","Pink","Yellow","Red","Orange"}; //菜單項名稱
      ButtonGroup colorGroup=new ButtonGroup(); //實例化按鈕組
      popupMenu=new JPopupMenu(); //實例化彈出菜單
      items=new JRadioButtonMenuItem[5]; //初始化數組
      for (int i=0;i<items.length;i++) { 
         items[i]=new JRadioButtonMenuItem(str[i]); //實例化菜單項
         popupMenu.add(items[i]); //增加菜單項到菜單上
         colorGroup.add(items[i]); //增加菜單項到按鈕組
        items[i].addActionListener(action); //菜單項事件處理
      }     

      addMouseListener(new MouseAdapter(){  //窗口的鼠標事件處理
        public void mousePressed( MouseEvent event ) {  //點擊鼠標
           triggerEvent(event);  //調用triggerEvent方法處理事件
        } 

        public void mouseReleased( MouseEvent event ) { //釋放鼠標
           triggerEvent(event); 
        } 

        private void triggerEvent(MouseEvent event) { //處理事件
           if (event.isPopupTrigger()) //如果是彈出菜單事件(根據平臺不同可能不同)
              popupMenu.show(event.getComponent(),event.getX(),event.getY());  //顯示菜單
        }
    }); 

	getContentPane().setBackground(Color.white); //窗口的默認背景色為白色
    setSize(230,160); //設置窗口大小
    setVisible(true); //設置窗口為可視
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE ); //關閉窗口時退出程序
   }

   class ChangeColorAction implements ActionListener { //菜單項事件處理
      public void actionPerformed(ActionEvent event)   {
         for (int i=0;i<items.length;i++)
            if (event.getSource()==items[i]) { //判斷事件來自于哪個菜單項
               getContentPane().setBackground(colors[i]); //設置窗口背景
               repaint(); //重繪窗口
               return;
         }
      }
   }  
   
   public static void main( String args[])   {
      new JPopMenuDemo();      
   }
}