Problem in collision between objects

[Chetans]

Hi
I am creating Game
in which i am getting problem in collision detection
and threading
Game has a spaceship and number of obstacles
i want to detect the collision between them
How can i do this?

Following is my code :

package Game;
import java.applet.Applet;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.MediaTracker;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.net.MalformedURLException;
import java.net.URL;

public class ThreadInApplet extends Applet implements KeyListener
{
    private static final long serialVersionUID = 1L;
    
    Image[] asteroidImage;
    Image spaceshipImage;
     
    int[] XPosObst,YPosObst;
    int numberOfObstacles=0,XPosOfSpaceship,YPosOfSpaceship;
    int spaceButtnCntr=0,noOfObstaclesLevel=20;
   
    boolean gameStart=false,collideUp=false,collideDown=false,collideLeft=false,collideRight=false;
    
    private Image offScreenImage;
    private Dimension offScreenSize,d;
    private Graphics offScreenGraphics;

    int speedObstacles=1;
    String spaceshipImagePath="images/spaceship.png",obstacleImagepath="images/asteroid.png";
    String buttonToStart="Press Space to start";
    
    public void init()
    { 
            try 
            {
                 asteroidImage=new Image[noOfObstaclesLevel];
                 XPosObst=new int[noOfObstaclesLevel];
                 YPosObst=new int[noOfObstaclesLevel];
                 XPosOfSpaceship=getWidth()/2-35;
                 YPosOfSpaceship=getHeight()-100;
                 spaceshipImage=getImage(new URL(getCodeBase(),spaceshipImagePath));
                 for(int i=0;i<noOfObstaclesLevel;i++)
                 {
                     asteroidImage[i]=getImage(new URL(getCodeBase(),obstacleImagepath));  
                     XPosObst[i]=(int) (Math.random()*700);
                     YPosObst[i]=0;
                 }
                 MediaTracker tracker = new MediaTracker (this);
                 for(int i=0;i<noOfObstaclesLevel;i++)
                 {
                     tracker.addImage (asteroidImage[i], 0);
                 }
            
            } 
            catch (MalformedURLException e) 
            {
                e.printStackTrace();
            }
            setBackground(Color.black);
            addKeyListener(this);
            
            
    }
    
    
    public void paint(Graphics g)
    { 
        g.setColor(Color.white);
        if(gameStart==false)
            {
                g.drawString(buttonToStart, (getWidth()/2)-60, getHeight()/2);
            }
        g.drawString("HEADfitted Solutions Pvt.Ltd.", (getWidth()/2)-80, getHeight()-20);
        
        for(int n=0;n<numberOfObstacles;n++)
        {
            if(n>0)
            	g.drawImage(asteroidImage[n],XPosObst[n],YPosObst[n],this);
        }
        g.drawImage(spaceshipImage,XPosOfSpaceship,YPosOfSpaceship,this);

    }
    
	@SuppressWarnings("deprecation")
	public void update(Graphics g)
    {
        d = size();
        if((offScreenImage == null) || (d.width != offScreenSize.width) || (d.height != offScreenSize.height))
        {
	        offScreenImage = createImage(d.width, d.height);
	        offScreenSize = d;
	        offScreenGraphics = offScreenImage.getGraphics();
        }

	    offScreenGraphics.clearRect(0, 0, d.width, d.height);
	    paint(offScreenGraphics);
	    g.drawImage(offScreenImage, 0, 0, null);
    }

    
    public void keyReleased(KeyEvent arg0){}
    public void keyTyped(KeyEvent arg0) {}
    
    Thread mainThread=new Thread()
    {
        
		synchronized public void run () 
        {
              try     
                    {
            	  		
            	  		
                      //System.out.println("in main thread");
                      if (gameStart==true)
                      {
                    	  moveObstacles.start();
                    	  if(collide()==false)
	          	  			{
	          	  				createObsThread.start();
	          	  			}
	                   } 
                      
                    }
                    catch (Exception e) 
                    {
                        e.printStackTrace();
                    }
		                       
        }
    };
    
    Thread createObsThread=new Thread()
    {
        synchronized public void run () 
        {
        	 if (spaceButtnCntr==1)
             {
        		 if (collide()==false)
        		 {
        		    for(int g=0;g<noOfObstaclesLevel;g++)
                   {
		                        try     
		                        {
		                            sleep(1000);
		                        } 
		                        catch (InterruptedException e) 
		                        {
		                            e.printStackTrace();
		                        }
		                       numberOfObstacles++;
                   	 }
                   
                 }
        		
        		 }
        }
    };
    
   Thread moveObstacles=new Thread() // Moving Obstacle images downwards after every 10 ms
           {
				synchronized public void run () 
               {
                   while(YPosObst[19]!=600)
                   {
                	   if (collide()==false)
                	   {
                   		 	//createObsThread.start();
		                        for(int l=0;l<numberOfObstacles;l++)
		                        {
		                            YPosObst[l]+=speedObstacles;
		                           
		                        }
		                        repaint();
		                        try 
		                        {
		                            sleep(10);
		                        } 
		                        catch (InterruptedException e)
		                        {
		                            e.printStackTrace();
		                        }
                   	 } 
					
                	   
                   }
               }
               
           };
    
      
	public void keyPressed(KeyEvent e)
    {
		
        if(e.getKeyCode()==32)
        {
            gameStart=true;
            spaceButtnCntr++;
          
            if (spaceButtnCntr==1)
            {
            	 mainThread.start();
            	 
	        }
        }
        
        if(gameStart==true) 
        {
        	

            if(e.getKeyCode()==37 && collideLeft==false)//Spaceship movement left
            {
                new Thread () 
                {
                    synchronized public void run () 
                    {
                       XPosOfSpaceship-=10;
                        repaint();
                    }
                }.start();
            }
            if(e.getKeyCode()==38 && collideUp==false)//Spaceship movement up
            {
                new Thread () 
                {
                    synchronized public void run () 
                    {
                        YPosOfSpaceship-=10;
                        repaint();
                    }
                }.start();
            }
            if(e.getKeyCode()==39 && collideRight==false)//Spaceship movement right
            {
                new Thread () 
                {
                    synchronized public void run () 
                    {
                       XPosOfSpaceship+=10;
                        repaint();
                    }
                }.start();
            }
            if(e.getKeyCode()==40 && collideDown==false)//Spaceship movement down
            {
                new Thread () 
                {
                    synchronized public void run () 
                    {
                        YPosOfSpaceship+=10;
                        repaint();
                    }
                }.start();
            }
        }  
    }
	/*public boolean collide() 
    { 
		int x0, y0, w0, h0, x2, y2, w2, h2;
		x0=XPosOfSpaceship;
		y0=YPosOfSpaceship;
		h0=spaceshipImage.getHeight(null);
		w0=spaceshipImage.getWidth(null);
		 
		 for(int i=0;i<20;i++)
         {
             x2=XPosObst[i];
             y2=YPosObst[i];
             h2=asteroidImage[i].getHeight(null);
             w2=asteroidImage[i].getWidth(null);
             
             if ((x0 > (x2 + w2)) || ((x0 + w0) < x2)) return false;
             System.out.println(x2+" "+y2+" "+h2+" "+w2);
         	 if ((y0 > (y2 + h2)) || ((y0 + h0) < y2)) return false;        
                 
         }
		 return true;
	
    }*/
	public boolean collide()
    {
        int x1,y1,x2,y2,x3,y3,x4,y4;    //coordinates of obstacles 
        int a1,b1,a2,b2,a3,b3,a4,b4;    //coordinates of spaceship
        a1 =XPosOfSpaceship;
        b1=YPosOfSpaceship;
        a2=a1+spaceshipImage.getWidth(this);
        b2=b1;
        a3=a1;
        b3=b1+spaceshipImage.getHeight(this);
        a4=a2;
        b4=b3;
        for(int a=0;a<numberOfObstacles;a++)
        {
            x1 =XPosObst[a];
            y1=YPosObst[a];
            x2=x1+asteroidImage[a].getWidth(this);
            y2=y1;
            x3=x1;
            y3=y1+asteroidImage[a].getHeight(this);
            x4=x2;
            y4=y3;
            
            if(x1>=a1 && x1<=a2 && x1<=b3 && x1>=b1)
            	return (true);
            if(x2>=a1 && x2<=a2 && x2<=b3 && x2>=b1)
            	return(true);
            
            //********checking asteroid touch spaceship from up direction******** 
            if(y3==b1 && x4>=a1 && x4<=a2)
            {
                collideUp = true;
                return(true);
                
                
            }
            if(y3==b1 && x3>=a1 && x3<=a2)
            {
                collideUp = true;
                return(true);
                
            }
            
            //********checking asteroid touch spaceship from left direction******
            if(x2==a1 && y4>=b1 && y4<=b3)
            {
                collideLeft=true;
                return(true);
                
            }
            if(x2==a1 && y2>=b1 && y2<=b3)
            {
                collideLeft=true;
                return(true);
            }
            
            //********checking asteroid touch spaceship from right direction*****
            if(x1==a2 && y3>=b2 && y3<=b4)
            {
                collideRight=true;
                return(true);
            }
            if(x1==a2 && y1>=b2 && y1<=b4)
            {
                collideRight=true;
                return(true);
            }
            
            //********checking asteroid touch spaceship from down direction*****
            if(y1==b3 && x2>=a3 && x2<=a4)
            {
                collideDown=true;
                return(true);
            }
            if(y1==b3 && x1>=a3 && x1<=a4)
            {    
                collideDown=true;
                return(true);
            }
            else
            {
                collideUp=false;
                collideDown=false;
                collideLeft=false;
                collideRight=false;
            }
            
            

        }
         return(false);
    }
}

[programmer_007]

try and try until u succedd!

[Chetans]

try and try until u succedd!

Plz help me to solve this problem
i hve tried so much

[j2me64]

Hi Chetans

i can't help you because i have just begun with programming java games. but if you enter java collision detect in google you will get a lot of hits. believe me, you are not the first programmer having this problem ...