org.vectomatic.svg.edit.client.utils.ImageLoader.java Source code

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Here is the source code for org.vectomatic.svg.edit.client.utils.ImageLoader.java

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/**********************************************
 * Copyright (C) 2011 Lukas Laag
 * This file is part of svgreal.
 * 
 * svgreal is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * svgreal is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with svgreal.  If not, see http://www.gnu.org/licenses/
 **********************************************/
package org.vectomatic.svg.edit.client.utils;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.vectomatic.svg.edit.client.SvgrealApp;

import com.google.gwt.event.dom.client.LoadEvent;
import com.google.gwt.event.dom.client.LoadHandler;
import com.google.gwt.event.logical.shared.HasInitializeHandlers;
import com.google.gwt.event.logical.shared.InitializeEvent;
import com.google.gwt.event.logical.shared.InitializeHandler;
import com.google.gwt.event.shared.GwtEvent;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.resources.client.ImageResource;

/**
 * Class to preload a list of images
 * @author laaglu
 */
public class ImageLoader implements HasInitializeHandlers {
    protected List<SimpleImage> images;
    protected ImageResource[] resources;

    /**
     * Constructor
     */
    public ImageLoader() {
        images = new ArrayList<SimpleImage>();
        resources = new ImageResource[0];
    }

    /**
     * Preloads the specified images, asynchronously. Once loaded, a
     * {@link com.google.gwt.event.dom.client.LoadEvent} is fired.
     * @param resources
     * The images to preload.
     */
    public void loadImages(ImageResource[] resources) {
        images.clear();
        this.resources = resources;
        readNext();
    }

    private void readNext() {
        if (images.size() < resources.length) {
            final SimpleImage image = new SimpleImage();
            images.add(image);
            image.addLoadHandler(new LoadHandler() {
                @Override
                public void onLoad(LoadEvent event) {
                    readNext();
                }
            });
            image.setSrc(resources[images.size() - 1].getSafeUri().asString());
        } else {
            InitializeEvent.fire(this);
        }
    }

    /**
     * Returns the preloaded images.
     * @return the preloaded images.
     * @throws IllegalStateException if this method is
     * invoked synchronously before the 
     * {@link com.google.gwt.event.dom.client.LoadEvent} has been fired.
     */
    public Map<ImageResource, SimpleImage> getImages() {
        if (resources.length != images.size()) {
            throw new IllegalStateException();
        }
        Map<ImageResource, SimpleImage> resourceToImage = new HashMap<ImageResource, SimpleImage>();
        for (int i = 0; i < resources.length; i++) {
            resourceToImage.put(resources[i], images.get(i));
        }
        return resourceToImage;
    }

    @Override
    public void fireEvent(GwtEvent<?> event) {
        SvgrealApp.getApp().getEventBus().fireEventFromSource(event, this);

    }

    @Override
    public HandlerRegistration addInitializeHandler(InitializeHandler handler) {
        return SvgrealApp.getApp().getEventBus().addHandlerToSource(InitializeEvent.getType(), this, handler);
    }
}