Java example source code file (ImageObserver.java)

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abort, allbits, awt, error, framebits, height, imageobserver, properties, somebits, width

The ImageObserver.java Java example source code

/*
 * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.awt.image;

import java.awt.Image;


/**
 * An asynchronous update interface for receiving notifications about
 * Image information as the Image is constructed.
 *
 * @author      Jim Graham
 */
public interface ImageObserver {
    /**
     * This method is called when information about an image which was
     * previously requested using an asynchronous interface becomes
     * available.  Asynchronous interfaces are method calls such as
     * getWidth(ImageObserver) and drawImage(img, x, y, ImageObserver)
     * which take an ImageObserver object as an argument.  Those methods
     * register the caller as interested either in information about
     * the overall image itself (in the case of getWidth(ImageObserver))
     * or about an output version of an image (in the case of the
     * drawImage(img, x, y, [w, h,] ImageObserver) call).
     *
     * <p>This method
     * should return true if further updates are needed or false if the
     * required information has been acquired.  The image which was being
     * tracked is passed in using the img argument.  Various constants
     * are combined to form the infoflags argument which indicates what
     * information about the image is now available.  The interpretation
     * of the x, y, width, and height arguments depends on the contents
     * of the infoflags argument.
     * <p>
     * The <code>infoflags argument should be the bitwise inclusive
     * <b>OR of the following flags: WIDTH,
     * <code>HEIGHT, PROPERTIES, SOMEBITS,
     * <code>FRAMEBITS, ALLBITS, ERROR,
     * <code>ABORT.
     *
     * @param     img   the image being observed.
     * @param     infoflags   the bitwise inclusive OR of the following
     *               flags:  <code>WIDTH, HEIGHT,
     *               <code>PROPERTIES, SOMEBITS,
     *               <code>FRAMEBITS, ALLBITS,
     *               <code>ERROR, ABORT.
     * @param     x   the <i>x coordinate.
     * @param     y   the <i>y coordinate.
     * @param     width    the width.
     * @param     height   the height.
     * @return    <code>false if the infoflags indicate that the
     *            image is completely loaded; <code>true otherwise.
     *
     * @see #WIDTH
     * @see #HEIGHT
     * @see #PROPERTIES
     * @see #SOMEBITS
     * @see #FRAMEBITS
     * @see #ALLBITS
     * @see #ERROR
     * @see #ABORT
     * @see Image#getWidth
     * @see Image#getHeight
     * @see java.awt.Graphics#drawImage
     */
    public boolean imageUpdate(Image img, int infoflags,
                               int x, int y, int width, int height);

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the width of the base image is now available and can be taken
     * from the width argument to the imageUpdate callback method.
     * @see Image#getWidth
     * @see #imageUpdate
     */
    public static final int WIDTH = 1;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the height of the base image is now available and can be taken
     * from the height argument to the imageUpdate callback method.
     * @see Image#getHeight
     * @see #imageUpdate
     */
    public static final int HEIGHT = 2;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * the properties of the image are now available.
     * @see Image#getProperty
     * @see #imageUpdate
     */
    public static final int PROPERTIES = 4;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * more pixels needed for drawing a scaled variation of the image
     * are available.  The bounding box of the new pixels can be taken
     * from the x, y, width, and height arguments to the imageUpdate
     * callback method.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int SOMEBITS = 8;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * another complete frame of a multi-frame image which was previously
     * drawn is now available to be drawn again.  The x, y, width, and height
     * arguments to the imageUpdate callback method should be ignored.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int FRAMEBITS = 16;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * a static image which was previously drawn is now complete and can
     * be drawn again in its final form.  The x, y, width, and height
     * arguments to the imageUpdate callback method should be ignored.
     * @see java.awt.Graphics#drawImage
     * @see #imageUpdate
     */
    public static final int ALLBITS = 32;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * an image which was being tracked asynchronously has encountered
     * an error.  No further information will become available and
     * drawing the image will fail.
     * As a convenience, the ABORT flag will be indicated at the same
     * time to indicate that the image production was aborted.
     * @see #imageUpdate
     */
    public static final int ERROR = 64;

    /**
     * This flag in the infoflags argument to imageUpdate indicates that
     * an image which was being tracked asynchronously was aborted before
     * production was complete.  No more information will become available
     * without further action to trigger another image production sequence.
     * If the ERROR flag was not also set in this image update, then
     * accessing any of the data in the image will restart the production
     * again, probably from the beginning.
     * @see #imageUpdate
     */
    public static final int ABORT = 128;
}