A Slideshow Bean

Chapter 1 included a simple applet named Slideshow, which implemented the timed sequential display of several images. In this section, I convert Slideshow into a Java Bean, first changing its design to make it more generic:

Slideshow is now a subclass of Canvas, since it is no longer an independent applet. (A Canvas object represents a rectangular region on which you can print graphics and text.)
As an applet, the original class allowed the timer delay to be set as a parameter in the APPLET tag. Now that Slideshow is a Bean, the timing is managed as a property via the setDelay and getDelay methods.
Whereas the Slideshow applet loaded a predetermined set of images, SlideshowBean has an indexed property that can assign a set of Images for display, either through a constructor or via the setImages property method.
SlideshowBean has a new read-only property that retrieves the number of Images.
A SlideshowBean fires a SlideshowEvent object to designated Slideshow-
Listeners whenever the image changes (either because of a mouse click or a timer tick).

The SlideshowEvent class is defined by the following code.

package coyote.bean;

import java.util.*;
import java.awt.*;

//
//
// SlideshowEvent
//
//
public class SlideshowEvent extends EventObject
{

    //-------------------------
    // Fields
    //-------------------------
    private Image m_image;

    //-------------------------
    // Constructors
    //-------------------------
    public SlideshowEvent(Object obj, Image img)
    {
        super(obj);
        m_image = img;
    }

    //-------------------------
    // Properties
    //-------------------------
    public Image getEventImage()
    {
        return m_image;
    }

}

And a SlideshowListener class will implement this interface.

package coyote.bean;

//
//
// SlideshowListener
//
//
public interface SlideshowListener 
{

    void handleSlideshowEvent(SlideshowEvent event);

}

The new class, SlideshowBean, follows.

package coyote.bean;

// Import class packages
import java.applet.*;
import java.awt.*;
import java.beans.*;
import java.util.*;

public class SlideshowBean
    extends Canvas
    implements Runnable
{
    //-------------------------
    // Fields
    //-------------------------

    // Properties
    private long     m_delay = 5000;
    private int      m_nImages;
    private Image    m_Images[];  
    private int      m_nCurImage;
    private int      m_nImgWidth;
    private int      m_nImgHeight;
    private Vector   m_listeners;

    // Thread support
    Thread m_Slideshow = null;

    //-------------------------
    // Constructors
    //-------------------------
    public SlideshowBean()
    {
        m_nImages    = 0;
        m_nImgWidth  = 0;
        m_nImgHeight = 0;
        m_nCurImage  = 0;
        m_listeners  = new Vector();

        start();
    }

    public SlideshowBean(Image [] imgs)
    {
        m_listeners  = new Vector();
        setImages(imgs);

        start();
    }

    protected void finalize()
    {
        stop();
    }

    //-------------------------
    // Thread methods
    //-------------------------
    private void start()
    {
        m_Slideshow = new Thread(this);
        m_Slideshow.start();
    }

    public void stop()
    {
        if (m_Slideshow != null)
        {
            m_Slideshow.stop();
            m_Slideshow = null;
        }
    }

    //-------------------------
    // Properties
    //-------------------------
    public long getDelay()
    {
        return m_delay / 1000L;
    }

    public void setDelay(long sec)
    {
        m_delay = sec * 1000L; 
    }
    
    public Image [] getImages()
    {
        return m_Images;
    }

    public void setImages(Image [] imgs)
    {
        m_Images     = imgs;
        m_nImages    = imgs.length;
        m_nImgWidth  = m_Images[0].getWidth(this);
        m_nImgHeight = m_Images[0].getHeight(this);
        m_nCurImage  = 0;