关于JInternalFrame的问题

Question

import java.beans.*;
import javax.swing.*;
import java.awt.*;public class ClosingListener implements VetoableChangeListener{
        public void vetoableChange(PropertyChangeEvent e) throws PropertyVetoException{
                String name=e.getPropertyName();
                if(name.equals(JInternalFrame.IS_CLOSED_PROPERTY)){
                        Component c=(Component)e.getSource();
                        Boolean oldValue=(Boolean)e.getOldValue();
                        Boolean newValue=(Boolean)e.getNewValue();
                        if(oldValue==Boolean.FALSE&&newValue==Boolean.TRUE){
                                c.setVisible(true);
                                int select=JOptionPane.showConfirmDialog(c,"真的要退出吗？","系统消息",JOptionPane.YES_NO_OPTION,JOptionPane.QUESTION_MESSAGE);
                                if(select==JOptionPane.YES_OPTION){
                                        System.out.println("内部窗体已经关闭！");
                                }
                                else{
                                        throw new PropertyVetoException("close cancleled",e);
                                }
                        }
                }
        }
}
在你的内部窗体类中加入
this.addVetoableChangeListener(new ClosingListener());