iconkit.java

来自「开源（Open Source）项目JHotDraw的文档和源程序」· Java 代码 · 共 141 行

/*
 * @(#)Iconkit.java 5.2
 *
 */

package CH.ifa.draw.util;

import java.awt.*;
import java.awt.image.ImageProducer;
import java.util.*;

/**
 * The Iconkit class supports the sharing of images. It maintains
 * a map of image names and their corresponding images.
 *
 * Iconkit also supports to load a collection of images in
 * synchronized way.
 * The resolution of a path name to an image is delegated to the DrawingEditor.
 * <hr>
 * <b>Design Patterns</b><P>
 * <img src="images/red-ball-small.gif" width=6 height=6 alt=" o ">
 * <b><a href=../pattlets/sld031.htm>Singleton</a></b><br>
 * The Iconkit is a singleton.
 * <hr>
 */
public class Iconkit {
    private Hashtable           fMap;
    private Vector              fRegisteredImages;
    private Component           fComponent;
    private final static int    ID = 123;
    private static Iconkit      fgIconkit = null;
    private static boolean      fgDebug = false;

    /**
     * Constructs an Iconkit that uses the given editor to
     * resolve image path names.
     */
    public Iconkit(Component component) {
        fMap = new Hashtable(53);
        fRegisteredImages = new Vector(10);
        fComponent = component;
        fgIconkit = this;
    }

    /**
     * Gets the single instance
     */
    public static Iconkit instance() {
        return fgIconkit;
    }

    /**
     * Loads all registered images.
     * @see #registerImage
     */
    public void loadRegisteredImages(Component component) {
        if (fRegisteredImages.size() == 0)
            return;

        MediaTracker tracker = new MediaTracker(component);

        // register images with MediaTracker
        Enumeration k = fRegisteredImages.elements();
        while (k.hasMoreElements()) {
            String fileName = (String) k.nextElement();
            if (basicGetImage(fileName) == null) {
                tracker.addImage(loadImage(fileName), ID);
            }
        }
        fRegisteredImages.removeAllElements();

        // block until all images are loaded
        try {
            tracker.waitForAll();
        } catch (Exception e) {  }
    }

    /**
     * Registers an image that is then loaded together with
     * the other registered images by loadRegisteredImages.
     * @see #loadRegisteredImages
     */
    public void registerImage(String fileName) {
        fRegisteredImages.addElement(fileName);
    }

    /**
     * Registers and loads an image.
     */
    public Image registerAndLoadImage(Component component, String fileName) {
        registerImage(fileName);
        loadRegisteredImages(component);
        return getImage(fileName);
    }

    /**
     * Loads an image with the given name.
     */
    public Image loadImage(String filename) {
        if (fMap.containsKey(filename))
            return (Image) fMap.get(filename);
        Image image = loadImageResource(filename);
        if (image != null)
            fMap.put(filename, image);
        return image;
    }

    public Image loadImageResource(String resourcename) {
        Toolkit toolkit = Toolkit.getDefaultToolkit();
        try {
            java.net.URL url = getClass().getResource(resourcename);
            if (fgDebug)
                System.out.println(resourcename);
            return toolkit.createImage((ImageProducer) url.getContent());
        } catch (Exception ex) {
            return null;
        }
    }

    /**
     * Gets the image with the given name. If the image
     * can't be found it tries it again after loading
     * all the registered images.
     */
    public Image getImage(String filename) {
        Image image = basicGetImage(filename);
        if (image != null)
            return image;
        // load registered images and try again
        loadRegisteredImages(fComponent);
        // try again
        return basicGetImage(filename);
    }

    private Image basicGetImage(String filename) {
        if (fMap.containsKey(filename))
            return (Image) fMap.get(filename);
        return null;
    }
}