Category: Java

RTL support on android

Hola everyone,
Long time no see 😀 I was making an app based on hebrew language. Its true that hebrew is not fully supported on all android phones. On some device it may work RTL and on some hebrew won’t be supported at all. Anyway here i am again to share something that i learned. On devices that supported hebrew(rendering) had a minor issue, lets say there is a number 52 on a hebrew sentence and when u try to display this sentence then 52 number is displayed reverse i.e 25. Now just imagine how messed up will whole sentence be because of this reverse number. Thus i found loophole in new android RTL support. So i had to do something about it as this was full hebrew language based app. I was using textview to display this hebrew sentence and this sentence was coming from xml web service. So i came up with my awesome solution. I chose to use webview to render/display hebrew sentence with html formatting. SO my code looked like this to prepare html:

public static String BuildHtml(String hebrewText)
StringBuilder sb = new StringBuilder();
return sb.toString();

Now i load my html on a webview by calling my method that returns my hebrew string encoded in html format.

webView.loadData(BuildHtml(myHebrewText), "text/html", "utf-8");

This code worked flawlessly. The number 56 was getting displayed as 56 in a hebrew sentence.
I hope this helps those who faced simillar problem.


I have been doing game development on android very recently (2 weeks) :D. And i bought samsung galaxy having android 2.1 to test my games and demos. I am pretty happy with the results and enjoying very much. Before this i had made games for j2me mobile devices and still making. Well anyway i am not discussing android game development here so i am coming to the primary focus of this post.

Physics. Yeah physics is phun and if decent physics is added to your game then it makes game more enjoyable, of course if gameplay design is good and fun. I have been playing with my own very very basic physics code(collision detection, collision response) that i have written for j2me. It is working fine in android after tweaking my code here and there. But i wanted more features so i thought to look for any decent free opensource physics engine for android. Unfortunately i didn’t get much success. There were some forums and tutorials where using Box2d with android was discussed. This site has shown the tutorial using JBox2d on android and is been discussed by the people there.

I am a big fan of Box2d. I have been using JBox2d and Box2d flash for my respective platform based game. Library had fulfilled my satisfaction and need. I have not tested JBox2d on android yet. I wanted to do few research on it before doing that. In few forums people complained that if using more than 5 bodies, it brings the FPS rate down and makes simulation very slow. I haven’t checked that but is going to write code to see if its true. I think it may depend on hardware device specification and capability because i have played Angry Birds on my samsung galaxy s and physics of game works just fine and smooth. I came across one site where they showed the graph on how much number of bodies/elements effect the FPS(frame rate) using Box2d and Chipmunk. Here it is.

So now i am going to write a simple code of falling polygons using Box2d on android and see the FPS and performance. I will post the results and my experience on next post ASAP.

Merry Christmas & Happy New Year

2D Rain Effect

Hola Everyone.
I am working on a level for 2d game where i needed to add a rain effects. I am using Slick 2D library for making my 2d game. Before i started working on making 2D rain effect , i discussed this topic on slick 2d forum for how to get started ? Here is the forum thread. You can check it out.
So i wrote a simple code to create a rain effect:
1) Make a Rain Drop, i wrote a class for Rain Drop that extends Polygon class. Yes i m creating rain drops with polygons.
2) Create number of drops at random coordinates and simulate it across the screen i.e make them fall. You can use wind factor also for providing bit more interesting.

So this is the way i started.

Here is the Rain Drop class:

import org.newdawn.slick.geom.Polygon;

public class RainDrop extends Polygon{
public RainDrop(int size){

/** coordinates of vertices of polygon(rain drop) */
this.addPoint(0, 0);
this.addPoint(0, size);

This is the main class where we are using rain drops and simulating it to create a simple rain effect, nothing fancy.

import java.util.logging.Level;
import java.util.logging.Logger;
import org.newdawn.slick.AppGameContainer;
import org.newdawn.slick.BasicGame;
import org.newdawn.slick.Color;
import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.Image;
import org.newdawn.slick.SlickException;

public class Rainy extends BasicGame{

private RainDrop[] drops;
private Image background;

public Rainy(){

public static void main(String[] args){
try {
AppGameContainer app = new AppGameContainer(new Rainy());
app.setDisplayMode(1024, 768, true);
} catch (SlickException ex) {
Logger.getLogger(Rainy.class.getName()).log(Level.SEVERE, null, ex);

public void init(GameContainer gc) throws SlickException {
background=new Image("data/jungle.jpg");

/** creating 700 rain drops and placing it on random location across the screen */

public void update(GameContainer gc, int delta) throws SlickException {

for(int i=0;i768){

drops[i].setX((float) ((Math.random() * 2000)+30));

drops[i].setY((float) ((Math.random() * 5)));




public void render(GameContainer gc, Graphics g) throws SlickException {
g.drawImage(background, 0, 0);
g.setColor(new Color(188.0f,227.0f,229.0f,0.3f));
for(int i=0;i

So what i am doing :
1) initializeRain(int num_of_drops) takes an int parameter which denotes the number of rain drops. This function creates a number of rain drops(instance of raindrop class) and assigns the random x and y position to each rain drops.
2) Then we simply iterate the array of rain drops and translate them across the screen. When drops reaches the bottom of screen then we simply restore back to random initial starting postion. This keeps going on and gives the impression of rainy effect.

This is very simple 2d effect that i started with. You can write your own optimized version and can add more feature to give fancy impression like adding alpha values for each rain drop etc.


Hola EveryOne.

There are various methods/ways to detect a collision between two objects. Each having its own advantage and disadvantage and based on our requirement we implement one of the collsion detection algorithm.

Here i am not going to talk about collision algorithm. I am going to talk about determining the nearest object with which collision will take place. Suppose there are many objects across the screen and u have to detect the collision between your game character and those objects. And you run the algorithm to detect collision with each of every object in every frame. So it decreases the efficiency of your program. Its better to detremine the nearest object to your game character and detect collision with that determined nearest object.

Here i m using bounding rectangle concept for collision detection.

Code Example:

public static Sprite getNearestGroundSprite(ArrayList sprites,Sprite hero){
Sprite sprite=null;
float minDistance=9999;
for(int i=0;iscreenWidth || (sprites.get(i).getSX()+sprites.get(i).getWidth()<0)){ continue; } else /* ignore all those objects which are located above the game character */ if(hero.getSY()>sprites.get(i).getSY()){
/* ignore all those objects that are located at the left side of game character */
/* ignore all those objects that are located at right side of game character */

Sprite is just a class representing characters of game. getSX() and getSY() returns the x and y coordinate location of that sprite. getWidth() simply returns the width of the sprite image.

In above code i am ignoring all those sprites that are located at left, right and top of my game character because i need bottom sprite to check collision with i.e when character falls down. This way the number of sprites decreases for checking collisions. You can write function for finding nearest left and right sprites also. You need to call this function at right place and when needed.

This is very simple and basic way i started and it gets the job done. You can write your own optimized code. This is how i started. I have written my optimized code for finding nearest sprite but right now i won't be posting it but i'l share it soon in near future.



Hola everyone.

I am currently working on my own two game projects: one project is of mobile phone game and other is 2.5 or side-scrolling 3d game, not much sure. So for second project i am making an small engine that will be used to make 2.5D game or side scrolling 3d game, Just simple and fun game. I have chosen LWJGL, which is a java binding for Opengl to make my game. So first thing i need to work on loading images.texture mapping in lwjgl. I found some pretty much useful tutorials and great help from lwjgl forums. But atlast i got something that i was looking for from the forum.

I came to know about slick-util which is free and open source lib to load images and play sounds. Its very easy to pick up and implement it. Its just worked flawlessly and smoothly for me. You can download the slick-util from here. PNG, GIF, JPG, TGA are supported and WAV, OGG, XM sounds are supported by slick-util.

So here i’l show u how easily i loaded images and mapped to a 3D BOX. First u have to setup lwjgl and slick-util with netbeans. Yeah i am using netbeans to write my program. You can see my post to setup lwjgl with netbeans. Now we will set up slick-util, its a continuation to the steps that we did to setup lwjgl.


Step 1: We just have to configure the project properties so that project can find the lib to compile and run.



Ok that was it. Now slick-util lib has been set up.Now first i’l show u how to load image and bind it , full source will be at the end.

Texture texture;

Texture is an interface having description of texture which will be loaded.

texture = TextureLoader.getTexture(“PNG”, new FileInputStream(“Data/Crate.png”));

now we are loading the texture using TextureLoader utility class. Just smooth and simple.


Now we are binding the texture.

So thats what u need to load the image and map them to objects. Download this image to use it in this program.


Full Code:

* To change this template, choose Tools | Templates
* and open the template in the editor.

package com.gaanza.engine.test2;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.lwjgl.util.glu.GLU;
import org.newdawn.slick.opengl.Texture;
import org.newdawn.slick.opengl.TextureLoader;

* @author Java Guy
public class EngineTest {

private static boolean gameRunning=true;
private static int targetWidth = 800;
private static int targetHeight = 600;

private float xrot=0.1f;
private float yrot=0.1f;
private float zrot=0.1f;

/** The texture that's been loaded */
private Texture texture;

public static void main(String[] args){
EngineTest app=new EngineTest();

private static void initDisplay(boolean fullscreen){

DisplayMode chosenMode = null;

try {
DisplayMode[] modes = Display.getAvailableDisplayModes();

for (int i=0;i


On Forums, people keeps asking about setting up lwjgl library with netbeans. So here i am going to show the steps to do that.

STEP 1: Go to Tools-> Libariries.Now create new library. Give it a name say “lwjgl21”.


STEP 2: Now we have to configure the library. Click the classpath tab, then click add jars, and add all the jars shown below:


STEP 3: If u want to add java doc than click the javadoc tab, and then add the javadoc folder. Then finally click oK and lwjgl21 library that we have just created is done.

STEP 4: Now create a empty java project.


STEP 5: Now we have to set the properties so that our newly created project can find the lwjgl library and jar files. So Right-Click the project-> Properties. Now check the image carefully and configure accordingly. So first select libraries on the categories section and then click compile tab, and then add jar file for compilation step. This step is very important so check image properly below.


STEP 6: Okie now click run tab, and add the library that we had just created. Check the image very properly.


STEP 7: Now the final step. We have to provide the argument so that project cud find the necessary dll files. So first select the Run at caregories section then go to vm-options. Check the image properly and follow.


Okie thats it. Now click ok. So you have just set up lwjgl with your netbeans ide. So now you can compile and run your lwjgl app. I am using netbeans ide 6.7.



Here are the detailed steps to set up or install JOGL on your ubuntu. First of all you have to download the jogl library(according to your machine) from here . I am using Ubuntu 8.04 on intel board so i downloaded jogl-1.1.1-linux-i586.zip.

So extract the zip file. Now open the folder that you have just now extracted. Go to lib folder.

STEP 1: Now you have to copy four .so files i.e libjogl.so, libjogl_awt.so, libjogl_cg.so, libgluegen-rt.so to [javainstalation directory]/jre/lib/i386

Open the terminal window and type: sudo cp libjogl.so /usr/lib/java/jdk1.6.0_13/jre/lib/i386

similarly you have to copy other three .so files.

*you have to provide you java installation path*


Now you can check the destination if files has been copied.


STEP 2: Now copy jogl.jar and gluegen-rt.jar to [java installation di]/jre/lib/ext

run this command to copy: sudo cp jogl.jar /usr/lib/java/jdk1.6.0_13/jre/lib/ext

simillarly copy gluegen-rt.jar

*you have to provide your java installation path*


You can check:


STEP 3: SO thats it. Now lets test the simple jogl code.

import javax.media.opengl.GLCapabilities;

public class Hello{
public static void main (String args[]) {
try {
“Hello World! (The native libraries are installed.)”
GLCapabilities caps = new GLCapabilities();
“Hello JOGL! (The jar appears to be available.)”
} catch (Exception e) {

Now compile this Hello.java and the run it. Here is the output:


So thats it. Now your are off to fly and write your jogl apps.



When u install sun’s jdk manually on ubuntu, java classpath doesn’t get set automatically unlike in windows. So when you enter command javac in terminal window, it says “javac  command not found”. So here is the very simple way to set up the classpath for java on ubuntu.

STEP 1 : Open the terminal window.

STEP 2: Type sudo gedit /etc/bash.bash.rc. Press enter.

STEP 3: Now gedit editor will open up. Now at the end of file just write:


export PATH

**You have to provide the path of bin folder in java installation deirectory.**


STEP 4: Now save the file and close the editor and terminal. Open new terminal window and type javac and press enter, all the java options and flags will come up.

Thats it.