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I am working on a basic AI system to get an entity to follow a player. I created both the player and the ghost entity, but it seems as if the ghost only wants to increment both x and y, it never wants to do the opposite, or choose only x or y to use. Here is where I implemented the ghost and player in my constructor:

public MansionAzazel() {
    TileCoordinate ghostSpawn = new TileCoordinate(52, 50);
    TileCoordinate playerSpawn = new TileCoordinate(54, 52);
    player = new Player(playerSpawn.x(), playerSpawn.y(), key);
    ghost = new Ghost(ghostSpawn.x(), ghostSpawn.y(), player);

Here is the update() function for the ghost:

public void update() {
    int xa = 0, ya = 0;
    if (anim < 1000000)
        anim = 0;

    if (player.getX() > xa)
    if (player.getX() < xa)
    if (player.getY() > ya)
    if (player.getY() < ya)

    if (xa != 0 || ya != 0) {
        move(xa, ya);
        walking = true;
    } else
        walking = false;

In which to sum it all up, the ghost entity will only and always move in one direction because the coordinates are 0 and I don't know why.

share|improve this question
What is your question? – wes Aug 12 '13 at 18:50
It looks like your ghost update function uses player.getX() when checking for Y coordinates. You might want to fix that. Also, you should output what player.getX() and player.getY() returns in your ghost update function to see what you get. – UnderscoreZero Aug 12 '13 at 22:01
@UnderscoreZero I said that it returns -1 for both of them. I – Shzylo Aug 12 '13 at 22:04
What I meant was change the line System.out.println(xa + ", " + ya); to System.out.println(xa + ", " + ya + " " + player.getX() + ", " + player.getY()); – UnderscoreZero Aug 12 '13 at 22:14
@UnderscoreZero after I changed getX to getY from checking y coordinate they both print out positive 1 Also, I divided the player.getX() and player.getY() by 16 (tile size) it prints out the actual location, just not ghost. – Shzylo Aug 12 '13 at 22:14
up vote 1 down vote accepted

If the intent is the move the ghost toward the player and if the move() method moves the ghost (you haven't given us enough info to be sure), then perhaps the update() method should initialize xa and ya to ghost.getX() and ghost.getY(). It seems to reset xa and ya to 0 every time update() is called.

share|improve this answer
Based on how his player uses the move() function, that is most likely not going to do what you expect it to do. I am assuming his move function takes the current position and offsets it by xa and ya. This same update function was used for his player and it worked fine. – UnderscoreZero Aug 13 '13 at 15:46
Okay, @JMB you were quite right about that. It does reset the variables each time. Instead of using the my variables xa and ya I used this.getX() and this.getY() which worked perfectly! – Shzylo Aug 13 '13 at 16:16

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