Special Effects and Game Development in Java(TM) - The Applet SlideShow

import java.applet.*;

import java.awt.*;



public class slideshow extends Applet implements Runnable {



public Thread animationthread = null;

int maxitems=0;

int sleeptime=0;

Image images[];

int currentimage=0;



//The "next"-variables specifies what image

//that will be displayed and it's position.

int nextimage = 0;

int nextimagexposition = 0;

int nextimageyposition = 0;



public void init()

{

    maxitems=getIntegerParameter("maxitems",10);

    sleeptime=getIntegerParameter("sleeptime",10);

    images=new Image[maxitems];

    MediaTracker tracker=new MediaTracker(this);

    for (int i=0; i<maxitems; i++)
    {
        images[i]=getImage(getDocumentBase()
            ,getParameter("image"+i));
        tracker.addImage(images[i],i);
    }
    try {tracker.waitForAll();}
    catch(InterruptedException e)
    {
        System.out.println("Something happened while reading images...");
    }
}

public int getIntegerParameter(String name, int base)

{

    String value=getParameter(name);

    int intvalue;

    try {intvalue=Integer.parseInt(value,base);}

    catch (NumberFormatException e) {return 0;}

    return intvalue;

}



public void start()

{

    if (animationthread == null)

    {

         animationthread = new Thread(this,"animationthread");

         animationthread.start();

    }

}



public void stop()

{

    if ((animationthread != null) && animationthread.isAlive())

        animationthread.stop();

    animationthread = null;

}



public synchronized void paint(Graphics g)

{

    g.drawImage(images[currentimage],0,0,this);



    //The following image is drawn on top of the last

    //image.

    g.drawImage(images[nextimage]

         ,nextimagexposition,nextimageyposition,this);

}



public void update(Graphics g)

{

    paint(g);

}



public void run()

{

    //We must find out the applet's dimension and save it

    //in the "d" variable. We can now get the applet

    //width and height by writing d.width and d.height.

    Dimension d=size();



    //The "displacement" variables specify the

    //starting coordinates for the image.

    int displacementx=0;

    int displacementy=0;



    //"pathsize" will be used to know what distance

    //that the new image will be moved.

    int pathsize=0;



    //"currentimage" is initialized to the first image,

    //followed by the next image, who becomes image

    //number 2, and so on.

    currentimage=0;

    nextimage=1;

    while (true)

    {

        //We calculate from which direction that

        //the new image should be moved from.

        int directionx=(int) (Math.random()*3.0)-1;

        int directiony=(int) (Math.random()*3.0)-1;



        //"directionx" and "directiony" may have

        //three values: -1, 0 and 1. It is not

        //interesting if both variables get the value 0

        //at the same time so therefore we change

        //"directiony" so that the effect becomes

        //more interesting.

        if (directionx==0 && directiony==0) directiony=1;



        //The variable "pathsize" is set to the applet
        //width or height depending on what side is the
        //shortest.
        if (d.width<d.height) pathsize=d.width;
        else pathsize=d.height;
        displacementx=directionx*d.width;
        displacementy=directiony*d.height;



        //The following line is the protection to the
        //problem if the user should onlyu specify one
        //image.
        if (nextimage>maxitems-1) nextimage=0;



        //The following loop handles the screen update
        //during the animation. It will move the image
        //the number of times specifies by "pathsize",
        //which is the short side of the applet screen.
        for (int i=0; i<=pathsize; i++)
        {
            //The image positions are moved
            //with the fraction (i/pathsize).
            nextimagexposition=displacementx
                -directionx*(i*d.width)/pathsize;
            nextimageyposition=displacementy
                -directiony*(i*d.height)/pathsize;
            update(getGraphics());
            try {Thread.sleep(sleeptime);}
            catch(InterruptedException e) {}
        }
        //When the translation is finished,
        //then "currentimage" is set to the new
        //image.
        currentimage=nextimage;



        //We increase "nextimage" so that it points to the

        //next image. At the same time we make sure that

        //"nextimage" extends above the array index but

        //that it is forced to start over from 0 if it does.

        nextimage++;

        if (nextimage>maxitems-1) nextimage=0;

    }

}