menudragdemo.java

来自「《java事件处理指南》一书的代码,好东西」· Java 代码 · 共 84 行

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

public class MenuDragDemo extends JFrame
{
   private JMenuBar menuBar;
   private JMenu menu;
   private JMenuItem font10, font12, font14;
   private JLabel label;

   public MenuDragDemo() 
   {
/*  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 a MenuDragMouseListener.                         */

      font10 = new JMenuItem("10");
      font10.addMenuDragMouseListener(new MenuDragHandler());

      font12 = new JMenuItem("12");
      font12.addMenuDragMouseListener(new MenuDragHandler());

      font14 = new JMenuItem("14");
      font14.addMenuDragMouseListener(new MenuDragHandler());

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

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

      label = new JLabel("The Rain in Spain");
      label.setFont(new Font("Serif", Font.PLAIN, 12));
      label.setForeground(Color.black);
      label.setVerticalAlignment(SwingConstants.CENTER);
      label.setHorizontalAlignment(SwingConstants.CENTER);

      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 MenuDragMouseListener is implemented as an inner class.   */
/*  When the user drags the mouse through the items in the        */
/*  "Font Size" menu, MenuDragMouseEvents are generated and       */
/*  sent to the menuDragMouseEntered() method.  The font size     */
/*  of the label is updated to correspond with the menu item      */
/*  that generated the event.  The other three methods declared   */
/*  in the MenuDragMouseListener interface aren't used in this    */
/*  program, so they are implemented as stub methods.             */

   class MenuDragHandler implements MenuDragMouseListener
   {
      public void menuDragMouseEntered(MenuDragMouseEvent event) 
      {
         JMenuItem item = (JMenuItem)event.getComponent();
         label.setFont(new Font("Serif", Font.PLAIN, 
                       Integer.parseInt(item.getActionCommand())));
         invalidate();
         validate();
      }

      public void menuDragMouseDragged(MenuDragMouseEvent event) {}
      public void menuDragMouseExited(MenuDragMouseEvent event) {}
      public void menuDragMouseReleased(MenuDragMouseEvent event) {}
   }

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