Question

OK so I have this applet which lets a player move his 32×32 character between tiles … and anytime he is on the edge of the map then MOVES anywhere else… I get an ArrayIndexOutOfBounds exception. Also, when this happens, the character can walk through blocked tiles! However, this only happens on the east and south edges but on the south edge, the character CANNOT walk through blocked tiles upon moving away from the edge.

I don’t know how to fix this and maybe you could help me?

Here is an image of me explaining my problem:

Here is the code:

/** Tile Generator Programmer: Dan J.
Thanks to: g00se, pbl, Manny. Started
May 23, 2010
**/

import java.awt.; import
java.awt.event.; import
java.applet.Applet; import java.io.;
import java.util.;

public class tileGen extends Applet
implements KeyListener {

Image[] tiles; // tile arrays Image
player; // player image int x, y, px,
py, tx, ty; // x tile – y tile //
player x – player y // tile x – tile y
boolean left, right, down, up,
canMove, respawn; // is true? int[][]
board; // row tiles for ultimate
mapping experience! final int
NUM_TILES = 33; // how many tiles are
we implementing? Label lx, ly; // to
see where we are! int r1, r2,
u1,u2,l1,l2,d1,d2;

int lastX, lastY, row, col; Label
lbl1, lbl2, p1, p2;

public void init() {

board = loadBoard();

tiles = new Image[NUM_TILES];     for(int i = 0;i < NUM_TILES;i++) {
  tiles[i] = getImage(getClass().getResource(String.format("tiles/t%d.png",

i))); }

    player = getImage(getClass().getResource("player.png"));

// our player
addKeyListener(this);
canMove = true;
int spawnX = 4;
int spawnY = 4;
px =0;
py =0;
lastX = 0;
lastY= 0;
lbl1 = new Label(“LastX”, Label.LEFT);
lbl2 = new Label(“LastY”, Label.LEFT);

      p1 = new Label("X", Label.LEFT);
      p2 = new Label("Y", Label.LEFT);
       add(lbl1);
       add(lbl2);

       add(p1);
       add(p2);
       this.setFocusable( true );
}

private static final HashSet<Integer> BLOCKED_TILES = new

HashSet(); static {
BLOCKED_TILES.add(24);
BLOCKED_TILES.add(0);
BLOCKED_TILES.add(6);
BLOCKED_TILES.add(25);
BLOCKED_TILES.add(3); //add more
tiles here }

public void keyPressed(KeyEvent e) {

if (isInBound(lastX,lastY) == true) {
System.out.println(“\nYOU WENT OFF
THE GRID.\n”); }

  if (lastX > 0) {        r1 = lastX + 1;
  }else{      r1 = 0;         }       r2 = lastY;

  u1 = lastX;         if (lastY > 0) {         u2 = lastY - 1;         }else{
   u2 = 0;
   }



  if (lastX > 0) {        l1 = lastX - 1;
  }else{      l1 = 0;         }       l2 = lastY;

  d1 = lastX;         if (lastY > 0) {            d2

= lastY + 1; }else{ d2 = 0; }

  right = true;       left = true;        up =

true; down = true;

try { if (blocked(r1,r2) == true)
right = false; // we cannot go right
if (blocked(u1,u2) == true) up =
false; // we cannot go up if
(blocked(l1,l2) == true) left = false;
// we cannot go left if
(blocked(d1,d2) == true) down = false;
// we cannot go down

  }catch(ArrayIndexOutOfBoundsException

dap) { System.out.println(“Array Index
is Out of Bounds…:(\n” +
dap.getCause()); }

if (left == true) { if
(e.getKeyCode() == KeyEvent.VK_LEFT) {
left = true;
px = px – 32;
lastX = lastX – 1; } }

if (right == true) { if
(e.getKeyCode() == KeyEvent.VK_RIGHT)
{
right = true;
px = px + 32;
lastX = lastX + 1; } }

if (down == true) { if
(e.getKeyCode() == KeyEvent.VK_DOWN) {
down = true;
py = py + 32;
lastY = lastY + 1; } }

if (up == true) {

      if (e.getKeyCode() ==

KeyEvent.VK_UP) {
up = true;
py = py – 32;
lastY = lastY – 1; } }

String txtLastX =
Integer.toString(px);
lbl1.setText(txtLastX);

String txtLastY =
Integer.toString(py);
lbl2.setText(txtLastY);

String txtLastX1 =
Integer.toString(lastX);
p1.setText(txtLastX1);

String txtLastX2 =
Integer.toString(lastY);
p2.setText(txtLastX2); repaint();

} public void keyReleased(KeyEvent
e){

} // ignore public void
keyTyped(KeyEvent e){} // ignore

public void paint(Graphics g) {

    for (row = 0; row < board.length; row++) {
        for (col = 0; col < board[row].length; col++) {
            int index = board[row][col];
            g.drawImage(tiles[index], 32 * col, 32

* row, this);

        }
    }
    if (respawn == false) {
    g.drawImage(player, px, py, this);    }   if (respawn == true) {      

g.drawImage(player, 0,0, this);
System.out.println(“Respawned!”);
respawn = false; }
} // end paint method

 public void update(Graphics g)
 {
      paint(g);
 }

public int[][] loadBoard() {
    int[][] board = {
            { 2,2,24,24,24,24,24,1,3,0,0,0 },
            { 2,2,24,23,23,23,24,1,3,0,0,0 },
            { 1,1,24,23,23,23,24,1,3,3,3,1 },
            { 1,1,24,24,23,24,24,1,1,1,1,1 },
            { 1,1,1,1,7,1,1,1,1,1,1,1 },
            { 5,1,1,1,7,7,7,7,7,1,1,1 },
            { 6,1,3,1,1,1,3,1,7,7,7,1 },
            { 6,1,3,1,3,1,1,1,1,1,7,3 }
        };    return board;
}

public boolean blocked(int tx, int ty)
{ return
BLOCKED_TILES.contains(board[ty][tx]);
}

public boolean isInBound(int r, int
c) {
return (r >= 0) && (r < 8) && (c >= 12) && (c < 1); }

} // end whole thing

If this was solved, this would make me extremely not sad. 😀 I’m sure the problem lies within the map board tile… :\ My guess…

Thanks,
Dan

Answer 1

I quote:

if (lastX > 0) {        r1 = lastX + 1;
  }else{      r1 = 0;         }       r2 = lastY;

  u1 = lastX;         if (lastY > 0) {         u2 = lastY - 1;         }else{
   u2 = 0;
   }

You only increment X if it’s already greater than 0? I think you want to make sure it’s less than the biggest allowed value for x!

EDIT: In more detail:

Here’s your check for going right:

if (lastX > 0) {        r1 = lastX + 1;
  }else{      r1 = 0;         }       r2 = lastY;

  u1 = lastX;         if (lastY > 0) {         u2 = lastY - 1;         }else{
   u2 = 0;
   }

…and here’s your check for going left:

  if (lastX > 0) {        l1 = lastX - 1;
  }else{      l1 = 0;         }       l2 = lastY;

You’re checking the same thing in both cases! That’s got to be logically wrong. The first check is, in fact, the reason you get the exception going right: You ask if it’s safe to go left, then you go right!