imageiconproxy.java

《JAVA与模式》附书中源代码

package com.javapatterns.proxy.imageloader;

import java.awt.Graphics;
import java.awt.Component;
import javax.swing.ImageIcon;
import javax.swing.Icon;
import javax.swing.SwingUtilities;

public class ImageIconProxy implements Icon
{
   private ImageIcon realIcon = null;
   private String imageName;
   private int width;
   private int height;
   boolean isIconCreated = false;

   public ImageIconProxy(String imageName, int width, int height)
   {
      this.imageName = imageName;
      this.width = width;
      this.height = height;
   }

   public int getIconHeight()
   {
		return realIcon.getIconHeight();
   }

   public int getIconWidth()
   {
      	return realIcon.getIconWidth();
   }

   // The proxy's paint() method is overloaded to draw a border
   // and a message "Loading author's photo.." while the image
   // loads. After the image has loaded, it is drawn. Notice
   // that the proxy does not load the image until it is
   // actually needed.
   public void paintIcon(final Component c, Graphics g, int x, int y)
   {
      if(isIconCreated)
      {
         realIcon.paintIcon(c, g, x, y);
         g.drawString("Java and Patterns by Jeff Yan, Ph.D", x+20, y+370);
      }
      else
      {
         g.drawRect(x, y, width-1, height-1);
         g.drawString("Loading author's photo...", x+20, y+20);

         // The image is being loaded on another thread.
         synchronized(this)
         {
            SwingUtilities.invokeLater(new Runnable()
            {
                 public void run()
                 {
	                 try
                     {
	                    // Slow down the image-loading process.
	                    Thread.currentThread().sleep(2000);
	
	                    // ImageIcon constructor creates the image.
	                    realIcon = new ImageIcon(imageName);
	                    isIconCreated = true;
	                 }
	                 catch(InterruptedException ex)
	                 {
	                      ex.printStackTrace();
	                 }
	                 // Repaint the icon's component after the
	                 // icon has been created.
	                 c.repaint();
                }
            });
         }
      }
   }
}