Thread: Help With Moving A 2D Array Of Rectangles

Hi, I am working on a basic space invaders app for an into to java class I'm taking. Here is my issue:

I have a main class called SpaceInvaders. This controls all of the objects in the program(missiles, space invaders, your ship) while the other classes create those objects. Currently I have all of the alien ships stored in a class called Aliens. They are created by using a basic 2D rectangle array. Back in SpaceInvaders I have a method called animateAliens which is supposed to make them move. To create the squadron of aliens I have an instance variable in my SpaceInvaders class:

private Aliens squadron.

I cannot, for the life of me, figure out how to get the aliens to move. I cant set the location of the pieces of the array directly from SpaceInvaders because the array is actually made in Aliens. I have posted the code for SpaceInvaders, Aliens, and my Missile class so you can compile it. Please help! I am very stuck!

/**
 * SpaceInvaders.java 
 * 
 * @author William
 * @class CS
 * @assignment prog12
 * @due 4/24/2012
 * 
 */
 
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Imports
import wheelsunh.users.*;
import java.awt.event.*;
import java.util.*;
import java.awt.Color;
 
public class SpaceInvaders implements Animator, KeyListener
{  
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Static Class Variables  
 public static final int FRAME_WIDTH=652;
 public static final int FRAME_HEIGHT=650;
 private static int cols=11;
 private static int rows=5;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Instance Variables
 private AnimationTimer timer;
 private Aliens squadron = null;
 private Vector<Missile> missiles;
 private Rectangle defender;
 private static final int LEFT=37, UP=38, RIGHT=39;
 private int playerScore=0, deltaX=5, alienMoveCount=0, deltaY=0;
 private Color defenderColor=Color.blue;
 private boolean tempvar=true;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Default Constructor
 public SpaceInvaders() 
 {  
  squadron=new Aliens(); 
  defender=new Rectangle(250,550);     
 
  defender.setColor(defenderColor);
  defender.setSize( 50, 30);
 
  // initialize the Vector of missiles to an empty Vector    
  missiles=new Vector<Missile>();
 
  // create the timer and have it call animate on this animator
  timer=new AnimationTimer(10,this);
 
  // start the animation
  timer.start();
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Animation Method
 // For every missile in the Vector
 // call its "step" method and call the method
 // this.checkMissile( Missile )
 public void animate()
 {  
  while(tempvar==true);
   animateAliens();
  for(int i=0;i<missiles.size();i++)
   animateMissile(missiles.get(i));
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Animates the aliens
 public void animateAliens()
 {
  System.out.println("Animating");
  for(int r=0;r<rows;r++)
  {
    System.out.println("Row Loop");
   for(int c=0;c<cols;c++)
   {
     System.out.println("Column Loop");
    if(alienMoveCount%8==0)
    {
     System.out.println("moving y axis");     
     squadron[r][c].setLocation(squadron[r][c].getXLocation(), squadron[r][c].getYLocation()+deltaY);
     deltaX=-deltaX;
     alienMoveCount=0;
    }
    else
    {
      System.out.println("Moving x axis");
     squadron[r][c].setLocation(squadron[r][c].getXLocation()+deltaX, squadron[r][c].getYLocation());
     alienMoveCount+=1;
    }
   }
  }
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Animates the Missile
 // First call missile.step() to move the missile then 
 // Check to see if the missile hit an enemy ship 
 // if it has then hide, set, and remove it from the vector
 public void animateMissile(  Missile missile )
 {
  missile.step();
  if(squadron.checkMissileStrike(missile.getLocation()))
  {
   playerScore+=10;
   missile.hide();
   missiles.remove(missile);
  }  
 
  else if(missile.getYLocation()<0)
  {
   missile.hide();
   missiles.remove(missile);
  }
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Handles the movement of the defender
 public void keyPressed(KeyEvent e) 
 {
  int code = e.getKeyCode( );
 
  if(code==LEFT)
  {        
   if(defender.getXLocation()<0)
    {}
   else
    defender.setLocation(defender.getXLocation()-10,
                         defender.getYLocation());
  }
 
  else if(code==RIGHT)
  {
   if((defender.getXLocation()+defender.getWidth())>=FRAME_WIDTH)
    {}
   else
    defender.setLocation(defender.getXLocation()+
                         10,defender.getYLocation());
  }
 
  else if(code==UP)
  {
   if(missiles.size()!=0)
   {
    System.out.println("Only 1 missle can be shot at a time!");
   }
   else
   {
    Missile attackmissile = new Missile(defender.getXLocation()+
               defender.getWidth()/2, defender.getYLocation());
    missiles.add(attackmissile);
   }
  }
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Handles the keys hit
 public void keyTyped(KeyEvent e) 
 {
  // System.out.println( "XXKEY TYPED: " + e.getKeyCode( ) );
  // Not Used But Must Be Kept For KeyListener To Work
 }
 
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Handles the keys release
 public void keyReleased(KeyEvent e) 
 {
  // System.out.println("XXKEY RELEASED: " + e.getKeyCode( ) );
  // Not Used But Must Be Kept For KeyListener To Work
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 //Main
 public static void main( String args[ ] )
 {
  Frame f = new Frame( FRAME_WIDTH, FRAME_HEIGHT );
  SpaceInvaders app = new SpaceInvaders(  ); 
  f.addKeyListener( app );  
 }
}
//End Of SpaceInvaders.java

/**
 * Aliens.java 
 * 
 * @author William
 * @class CS
 * @assignment prog12
 * @due 4/24/2012
 * 
 */
 
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
//Imports
import wheelsunh.users.*;
import java.awt.Color;
import java.awt.Point;
 
public class Aliens 
{
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Class Variables
 private static int cols=11;
 private static int rows=5;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Instance Variables
 protected Rectangle[][] squadron; 
 private int alienWidth=36,alienHeight=24,hSpace=6,vSpace=20;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Default ConstructorCreates The Aliens Based Off Of The 
 // Instance Variables
 public Aliens(  )
 {
  squadron=new Rectangle[rows][cols];     
  for(int r=0;r<rows;r++)
  {
   for(int c=0;c<cols;c++)
   {
    Rectangle ship = new Rectangle();
    ship.setSize(alienWidth,alienHeight);
    ship.setLocation(c*(alienWidth+hSpace),
                     r*(alienHeight+vSpace));
    ship.setColor(Color.RED);
    squadron[r][c]=ship; 
   }
  }
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 //Checks For Missile Strikes With Aliens
 public boolean checkMissileStrike( Point p )
 {
  for(int r=0;r<5;r++)
  {
   for(int c=0;c<11;c++)
   {
    if(squadron[r][c].contains(p))
    {
     System.out.println("Row: "+r+", Column: "+c);
     squadron[r][c].setLocation(-100,-100);
     return true;
    }
   }      
  }
  return false;
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 //Main
 public static void main(String[] args) 
 {
  new Frame();
  new Aliens();
 }  
}
//End Of Aliens.java

/**
 * Missile.java 
 * 
 * @author William 
 * @class CS
 * @assignment prog12
 * @due 4/24/2012
 * 
 */
 
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// Imports
import wheelsunh.users.*;
import java.awt.Color;
 
public class Missile extends ShapeGroup
{
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Static Class Variables  
 public static final int FRAME_WIDTH=652;
 public static final int FRAME_HEIGHT=650;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Instance Variables
 private RoundedRectangle body;
 private int deltaY=-5, bodyX=4, bodyY=25;
 private Color bodyColor=Color.green, frameColor=Color.orange;
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Default Constructor
 public Missile(int x, int y)
 {
  body=new RoundedRectangle(0, 0);
  body.setFillColor(bodyColor);
  body.setFrameColor(frameColor);
  body.setSize(bodyX,bodyY); 
  add(body);     
  setLocation(x,y);
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Moves The Missile
 public void step()
 {
  setLocation(getXLocation(), getYLocation() + deltaY);
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Hides The Missile
 public void hide( )
 {
  body.hide();
 }
 
 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 // Main
 public static void main(String[] args)
 {
  Frame f = new Frame(FRAME_WIDTH, FRAME_HEIGHT);
  SpaceInvaders app = new SpaceInvaders(); 
  f.addKeyListener(app);  
 }   
}
//End Of Missile.java

*Edited to remove my name

The usual way for one class to access methods or data in another class is by getting a reference to the class with the data and using that to call accessor methods to get/set the data.

In the class with method where you want to get to the data, is there a way that the class can have a reference to the class with the data? For example the reference to the class with the data could be passed in the constructor of the class where you need the reference and the constructor could save it in a class variable so all its methods could use it.