Developer CD Series 2000 November: Tool Chest/Dev.CD Nov 00 TC Disk 2.toast/pc/sample code/quicktime/quicktime for java/zoo tutorial/module10- qtzoo/completed source/buffereddrawer.java

Java Source | 2000-09-28 | 5.4 KB | 139 lines

import java.awt.Container;
import java.awt.Image;
import java.awt.Graphics;
import java.awt.Dimension;

/**
 * A component which does all its drawing in an offscreen image
 * the size of the component.
 *
 * @author Levi Brown
 * @author Apple Worldwide Developer Technical Support
 * @author Apple Computer Inc.
 * @version 1.0 11/4/1998
 * Copyright:     © Copyright 1999 Apple Computer, Inc. All rights reserved.
 *
 * Disclaimer:    IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.
 *                ("Apple") in consideration of your agreement to the following terms, and your
 *                use, installation, modification or redistribution of this Apple software
 *                constitutes acceptance of these terms.  If you do not agree with these terms,
 *                please do not use, install, modify or redistribute this Apple software.
 *
 *                In consideration of your agreement to abide by the following terms, and subject
 *                to these terms, Apple grants you a personal, non-exclusive license, under Apple’s
 *                copyrights in this original Apple software (the "Apple Software"), to use,
 *                reproduce, modify and redistribute the Apple Software, with or without
 *                modifications, in source and/or binary forms; provided that if you redistribute
 *                the Apple Software in its entirety and without modifications, you must retain
 *                this notice and the following text and disclaimers in all such redistributions of
 *                the Apple Software.  Neither the name, trademarks, service marks or logos of
 *                Apple Computer, Inc. may be used to endorse or promote products derived from the
 *                Apple Software without specific prior written permission from Apple.  Except as
 *                expressly stated in this notice, no other rights or licenses, express or implied,
 *                are granted by Apple herein, including but not limited to any patent rights that
 *                may be infringed by your derivative works or by other works in which the Apple
 *                Software may be incorporated.
 *
 *                The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO
 *                WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED
 *                WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 *                PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN
 *                COMBINATION WITH YOUR PRODUCTS.
 *
 *                IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR
 *                CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 *                GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *                ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION
 *                OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF CONTRACT, TORT
 *                (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN
 *                ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
public class BufferedDrawer extends Container
{
    /**
     * Creates a new BufferedDrawer.
     */
    public BufferedDrawer()
    {
        //Initialize our data members
        workingGraphics     = null;
        workingImage        = null;
    }

    /**
     * Handles drawing the desired content into the offscreen buffer.
     * Override this to do your own drawing (be sure to call super.draw()).
     * @see #paint
     */
    protected void draw()
    {
        //Make sure the offscreen image is ready to be drawn into.
        ensureValidWorkingImage();

        //Do drawing here (use workingGraphics)
        //Don't forget to erase the buffer if you don't draw over the entire area
        //or else you will end up with tracers.
        //To erase the entire area, uncomment out the following code:
    }

    /**
     * Makes sure the offscreen image exists.
     */
    protected void ensureValidWorkingImage()
    {
        //If the size changed and we need to create a new pane image, then create one
        Dimension size = getSize();
        if ((size != null && size.width > 0 && size.height > 0) && (workingImage == null || size.width != workingImage.getWidth(this) || size.height != workingImage.getHeight(this)))
        {
            if (workingImage != null)
            {
                workingImage.flush();
                workingImage = null;
            }
            workingImage = createImage(size.width, size.height);
            if (workingGraphics != null)
            {
                workingGraphics.dispose();
                workingGraphics = null;
            }
            workingGraphics = workingImage == null ? null : workingImage.getGraphics();
        }
    }

    /**
     * Updates the component. This method is called in
     * response to a call to repaint. You can assume that
     * the background is not cleared.
     * Overriden here to prevent unwanted background erasing.
     * @param g the specified Graphics window
     * @see #paint
     * @see java.awt.Component#repaint
     */
    public void update(Graphics g)
    {
        paint(g);
    }

    /**
     * Paints the component.  This method is called when the contents
     * of the component should be painted in response to the component
     * first being shown or damage needing repair.  The clip rectangle
     * in the Graphics parameter will be set to the area which needs
     * to be painted.
     * @param g the specified Graphics object
     * @see #update
     */
    public void paint(Graphics g)
    {
        draw();
        g.drawImage(workingImage, 0, 0, this);
        super.paint(g);
    }

    //The offscreen image buffer to render the progress bar into.
    protected Image workingImage;
    //The Graphics object associated with the offscreen image buffer.
    protected Graphics workingGraphics;
}