com.rcpcompany.utils.extensionpoints.CEResourceHolder.java Source code

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Here is the source code for com.rcpcompany.utils.extensionpoints.CEResourceHolder.java

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/*******************************************************************************
 * Copyright (c) 2006-2013 The RCP Company and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     The RCP Company - initial API and implementation
 *******************************************************************************/
package com.rcpcompany.utils.extensionpoints;

import java.net.MalformedURLException;
import java.net.URL;

import org.eclipse.core.runtime.FileLocator;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.Platform;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.swt.graphics.Image;
import org.osgi.framework.Bundle;

/**
 * Simple holder pattern for images in the extension registry.
 * <p>
 * Used to hold a reference to a resource that is created via the extension registry.
 * 
 * @author Tonny Madsen, The RCP Company
 */
public class CEResourceHolder {
    private final IConfigurationElement myCE;
    private ImageDescriptor myImageDescriptor = null;
    private Image myImage = null;
    private final String myAttrName;

    /**
     * Constructs and returns a new holder object for the specified configuration element.
     * <p>
     * Short for <code>CEObjectHolder(ce, "image")</code>
     * 
     * @param ce
     *            the configuration element
     */
    public CEResourceHolder(IConfigurationElement ce) {
        this(ce, "image");
    }

    /**
     * Constructs and returns a new holder object for the specified configuration element.
     * 
     * @param ce
     *            the configuration element
     * @param attrName
     *            the attribute name
     */
    public CEResourceHolder(IConfigurationElement ce, String attrName) {
        myCE = ce;
        myAttrName = attrName;
    }

    /**
     * Returns the image for the holder object.
     * 
     * @return the image or <code>null</code>
     */
    public Image getImage() {
        if (myImage == null) {
            final ImageDescriptor descriptor = getImageDescriptor();
            if (descriptor != null) {
                myImage = descriptor.createImage();
            }
        }
        return myImage;
    }

    /**
     * Returns the image descriptor for the holder object.
     * 
     * @return the image or <code>null</code>
     */
    public ImageDescriptor getImageDescriptor() {
        if (myImageDescriptor == null) {
            final String imageName = myCE.getAttribute(myAttrName);
            if (imageName == null)
                return null;
            final Bundle bundle = Platform.getBundle(myCE.getContributor().getName());
            URL url = FileLocator.find(bundle, new Path(imageName), null);
            if (url == null) {
                try {
                    url = new URL(imageName);
                } catch (final MalformedURLException e) {
                    return null;
                }

            }
            if (url == null)
                return null;

            myImageDescriptor = ImageDescriptor.createFromURL(url);
            ;

        }
        return myImageDescriptor;
    }
}