fileimagedescriptor.java

jfa2ce 源码帮助开发人员更好的理解运用

/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.resource;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.graphics.ImageData;

/**
 * An image descriptor that loads its image information
 * from a file.
 */
class FileImageDescriptor extends ImageDescriptor {

    /**
     * The class whose resource directory contain the file, 
     * or <code>null</code> if none.
     */
    private Class location;

    /**
     * The name of the file.
     */
    private String name;

    /**
     * Creates a new file image descriptor.
     * The file has the given file name and is located
     * in the given class's resource directory. If the given
     * class is <code>null</code>, the file name must be absolute.
     * <p>
     * Note that the file is not accessed until its
     * <code>getImageDate</code> method is called.
     * </p>
     *
     * @param clazz class for resource directory, or
     *   <code>null</code>
     * @param filename the name of the file
     */
    FileImageDescriptor(Class clazz, String filename) {
        this.location = clazz;
        this.name = filename;
    }

    /* (non-Javadoc)
     * Method declared on Object.
     */
    public boolean equals(Object o) {
        if (!(o instanceof FileImageDescriptor)) {
            return false;
        }
        FileImageDescriptor other = (FileImageDescriptor) o;
        if (location != null) {
            if (!location.equals(other.location)) {
                return false;
            }
        } else {
            if (other.location != null) {
                return false;
            }
        }
        return name.equals(other.name);
    }

    /* (non-Javadoc)
     * Method declared on ImageDesciptor.
     * Returns null if the image data cannot be read.
     */
    public ImageData getImageData() {
        InputStream in = getStream();
        ImageData result = null;
        if (in != null) {
            try {
                result = new ImageData(in);
            } catch (SWTException e) {
                if (e.code != SWT.ERROR_INVALID_IMAGE) {
					throw e;
                // fall through otherwise
				}
            } finally {
                try {
                    in.close();
                } catch (IOException e) {
                    //System.err.println(getClass().getName()+".getImageData(): "+
                    //  "Exception while closing InputStream : "+e);
                }
            }
        }
        return result;
    }

    /**
     * Returns a stream on the image contents.  Returns
     * null if a stream could not be opened.
     * 
     * @return the buffered stream on the file or <code>null</code>
     * if the file cannot be found
     */
    private InputStream getStream() {
        InputStream is = null;

        if (location != null) {
            is = location.getResourceAsStream(name);

        } else {
            try {
                is = new FileInputStream(name);
            } catch (FileNotFoundException e) {
                return null;
            }
        }
        if (is == null) {
			return null;
		} else {
			return new BufferedInputStream(is);
		}
    }

    /* (non-Javadoc)
     * Method declared on Object.
     */
    public int hashCode() {
        int code = name.hashCode();
        if (location != null) {
            code += location.hashCode();
        }
        return code;
    }

    /* (non-Javadoc)
     * Method declared on Object.
     */
    /**
     * The <code>FileImageDescriptor</code> implementation of this <code>Object</code> method 
     * returns a string representation of this object which is suitable only for debugging.
     */
    public String toString() {
        return "FileImageDescriptor(location=" + location + ", name=" + name + ")";//$NON-NLS-3$//$NON-NLS-2$//$NON-NLS-1$
    }
}