问答题

本题的功能是用复选按钮来控制鼠标右键的弹出菜单是否弹出。窗口中有一个复选按钮“弹出菜单”，如果选中该复选按钮后，鼠标置于窗口上，单击鼠标右键会弹出一个菜单，单击菜单项中的选项后，后台会输出单击的菜单项，如果取消该复选按钮的选择，单击鼠标右键则不能弹出菜单。
import java.awt.*;
import java.awt.event.*;
class CanvasWithPopup extends Canvas
Popupmenu popup;
CanvasWithPopup(PopupMenu popup)
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
this.popup=popup;
void addPopup()
add(popup);
void removePopup()
remove(popup);
protected void processMouseEvent(MouseEvent evt)
if(popup.getParent()!=null&&evt.isPopupTrigger())
popup.show(evt.getComponent(),evt.getX(),evt.getY());
super.processMouseEvent(evt);

public class java3 extends Frame implements ItemListener,ActionListener
Checkbox cb=new Checkbox("弹出菜单",false);
CanvasWithPopup canvas;
java3()
super("java3");
addWindowListener(new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
);
add(cb,BorderLayout.NORTH);
cb.addItemListener(this);
PopupMenu popup=new PopupMenu("Button Control");
popup.add("item1");
popup.add("item2");
popup.addActionListener(this);
canvas=new CanvasWithPopup(popup);
add(canvas,BorderLayout.CENTER);
setSize(100,200);
show();
public void itemStateChanged(ItemEVent evt)
switch(evt.getState())(
case ItemEvent.SELECTED:
canvas.addPopup();
break;
case ItemEvent.DESELECTED:
canvas.removePopup();
break;

public void actionPerformed(ActionEvent evt)
System.out.printlnCgetActionCommand()+"is seIected");
static public void main(String[]args)
new java3();