Home E-Books Special Effects and Game Development in Java The Applet SlideShow

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()




    images=new Image[maxitems];

    MediaTracker tracker=new MediaTracker(this);

    for (int i=0; i<maxitems; 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
if (d.width<d.height) pathsize=d.width;
else pathsize=d.height;
displacementy=directiony*d.height; //The following line is the protection to the
//problem if the user should onlyu specify one
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).
try {Thread.sleep(sleeptime);}
catch(InterruptedException e) {}
//When the translation is finished,
//then "currentimage" is set to the new
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; } }