imageiconproxy.java

《Java与模式》一书的源代码

package com.javapatterns.proxy.imageloader;

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

public class ImageIconProxy implements Icon
{
    private ImageIcon realIcon = null;
    private String imageName;
    private int width;
    private int height;
    private 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();
                        }
                    });
            }
        }
    }
}