menukeyeventdemo.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 MenuKeyEventDemo extends JFrame implements ActionListener
{
   private JMenuBar menuBar;
   private JMenu menu;
   private JMenuItem font10, font12, font14;
   private JLabel label;
   private int fontStyle, fontSize;

   public MenuKeyEventDemo() 
   {
      fontStyle = Font.PLAIN;
      fontSize = 12;

/*  A "Font Size" menu is created with three menu items.  The menu    */
/*  is intended to set the font size of a label. The three JMenuItem  */
/*  objects register an ActionListener.                               */

      font10 = new JMenuItem("10");
      font10.addActionListener(this);

      font12 = new JMenuItem("12");
      font12.addActionListener(this);

      font14 = new JMenuItem("14");
      font14.addActionListener(this);

/*  The three JMenuItem objects are placed inside a JMenu.  The JMenu  */
/*  registers a MenuKeyListener.                                       */

      menu = new JMenu("Font Size");
      menu.add(font10);
      menu.add(font12);
      menu.add(font14);
      menu.addMenuKeyListener(new MenuKeyHandler());

      menuBar = new JMenuBar();
      menuBar.add(menu);

      label = new JLabel("Java, Java, Java");
      label.setFont(new Font("Serif", fontStyle, fontSize));
      label.setForeground(Color.black);

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

      getContentPane().add(menuBar, BorderLayout.NORTH);
      getContentPane().add(panel, BorderLayout.CENTER);

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

/*  The MenuKeyListener is implemented as an inner class.  Whenever  */
/*  the menu display is visible and the user presses a key, the      */
/*  JMenu will generate a MenuKeyEvent and send it to the            */
/*  menuKeyPressed() method.  If the keystroke was 'b', the font     */
/*  type is set to Font.BOLD.  If the keystroke was 'p', the font    */
/*  type is set to Font.PLAIN.  The menuKeyReleased() and            */
/*  menuKeyTyped() methods are not used in this example, so they     */
/*  implemented as stub methods.                                     */

   class MenuKeyHandler implements MenuKeyListener
   {
      public void menuKeyPressed(MenuKeyEvent event) 
      {
         if ( event.getKeyCode() == KeyEvent.VK_B )
         {
            fontStyle = Font.BOLD;
         }
         if ( event.getKeyCode() == KeyEvent.VK_P )
         {
            fontStyle = Font.PLAIN;
         }
      }

      public void menuKeyReleased(MenuKeyEvent event) {}
      public void menuKeyTyped(MenuKeyEvent event) {}
   }

/*  When a menu item is selected, it generates an ActionEvent that is  */
/*  sent to the actionPerformed() method.  This method re-sets the     */
/*  font size of the label.                                            */

   public void actionPerformed(ActionEvent event)
   {
      fontSize = Integer.parseInt(event.getActionCommand());
      label.setFont(new Font("Serif", fontStyle, fontSize));
      invalidate();
      validate();
   }

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