popupmenudemo.java

《java事件处理指南》一书的代码,好东西

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

public class PopupMenuDemo extends JFrame 
{
   private JLabel label;
   private JPopupMenu menu;
   private JTextField jtf;

   public PopupMenuDemo() 
   {
/*  A JPopupMenu is created with two menu items.  The JPopupMenu   */
/*  registers a PopupMenuListener.                                 */

      menu = new JPopupMenu("menu");
      menu.add(new JMenuItem("open"));
      menu.add(new JMenuItem("quit"));
      menu.addPopupMenuListener(new PopupMenuHandler());

      label = new JLabel("Menu");
      label.setFont(new Font("Serif", Font.BOLD, 12));
      label.setForeground(Color.black);
      label.setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
      label.addMouseListener(new MouseHandler());

      jtf = new JTextField(15);
      jtf.setEditable(true);

      JPanel centerPanel = new JPanel();
      centerPanel.add(label);

      getContentPane().add(centerPanel, BorderLayout.CENTER);
      getContentPane().add(jtf, BorderLayout.SOUTH);

      setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      setBounds(100, 100, 300, 200);
      setVisible(true);
   }

/*  The PopupMenuListener is implemented as an inner class.   */
/*  When a PopupMenuEvent is generated, it is sent to one     */
/*  of the three listener methods.  The type of event is      */
/*  printed inside a textfield at the bottom of the frame.    */

   class PopupMenuHandler implements PopupMenuListener
   {
      public void popupMenuCanceled(PopupMenuEvent event)
      {
         jtf.setText("menu canceled");
      }

      public void popupMenuWillBecomeInvisible(PopupMenuEvent event)
      {
         jtf.setText("menu becoming invisible");
      }

      public void popupMenuWillBecomeVisible(PopupMenuEvent event)
      {
         jtf.setText("menu becoming visible");
      }
   }

/*  The MouseListener is used to detect the popup menu trigger  */
/*  When that happens, the popup menu is made visible.  All     */
/*  three types of non-motion oriented MouseEvents are tested   */
/*  because the popup menu trigger may be platform dependent.   */

   class MouseHandler extends MouseAdapter
   {
      public void mousePressed(MouseEvent event) 
      {
         testEvent(event);
      }

      public void mouseReleased(MouseEvent event) 
      {
         testEvent(event);
      }

      public void mouseTyped(MouseEvent event) 
      {
         testEvent(event);
      }

      private void testEvent(MouseEvent event)
      {
         if ( event.isPopupTrigger() )
         {
            menu.show(label, event.getX(), event.getY());
         }
      }
   }

   public static void main(String args[]) 
   {
      PopupMenuDemo demo = new PopupMenuDemo();
   }
}