How can I make an enemy follow a player but only up down left right? not diagonally?
dominicarrojado wrote ...
2013/9/1
Enemy Follow Player
Therefore you need to know the position of your enemy and the position of your player.
You have to get a reference to the player in your enemy object (see this greenfoot tutorial).
If you have got the reference you can use this code:
public void act() {
java.util.List<Player> playersInWorld = getWorld().getObjects(Player.class);
if (!playersInWorld.isEmpty()) {
Player player = playersInWorld.get(0);
moveToPlayer(player);
}
}
public void moveToPlayer(Player player) {
int deltaX = getX() - player.getX();
int deltaY = getY() - player.getY();
if (Math.abs(deltaX) > Math.abs(deltaY)) {
if (deltaX > 0) {
setLocation(getX() - 1, getY());
}
else if (deltaX < 0) {
setLocation(getX() + 1, getY());
}
}
else {
if (deltaY > 0) {
setLocation(getX(), getY() - 1);
}
else if (deltaY < 0) {
setLocation(getX(), getY() + 1);
}
}
}
With the code given by Gevator_Tod4711, your enemy will alternately move vertically and then horizontally when along one of the diagonals of the player. This will give the impression of moving diagonally, only a little slower and choppy.
Another way to handle it is with the following, which will probably be more along the lines of what you want:
// instance field to hold current axis to travel along
// (initial value randomly chosen)
private boolean movingVertically = Greenfoot.getRandomNumber(2) == 0;
;
// in act method, call a method to follow the player
followPlayer();
// the method to follow the player
private void followPlayer()
{
// do nothing if player not in world
if (getWorld.getObjects(Player.class).isEmpty()) return;
// get reference to Player object
Actor actor = (Actor)getWorld().getObjects(Player.class).get(0);
// give some randomness to follow direction by changing travel axis
// (the '100' can be adjusted to make changes occur slower or faster)
if (Greenfoot.getRandomNumber(100) == 0) movingVertically = Greenfoot.getRandomNumber(2) == 0;
// change axis if no movement required along current axis
if ((movingVertically && getY() == actor.getY()) || (!movingVertically && getX() == actor.getX())) movingVertically = !movingVertically;
// move along current axis
if (movingVertically) setLocation(getX(), getY()+(int)Math.signum(actor.getY()-getY()));
else setLocation(getX()+(int)Math.signum(actor.getX()-getX()), getY());
}Thanks that work!
Danpost in that code of yours, how can I make the enemy not pass if there's a wall?
I think the easyest way for doing this would be to override the setLocation method like this:
public void setLocation(int x, int y) {
if (getWorld().getObjectsAt(x, y, Wall.class).isEmpty()) {
super.setLocation(x, y);
}
}I have not tested it; but I think the following is what you want.
From line 19 above:
// determine possible movements
int dx = (int)Math.signum(actor.getX()-getX());
int dy = (int)Math.signum(actor.getY()-getY());
// do nothing if no movement
if (dx == 0 && dy == 0) return;
// check one way and if blocked check other way
int failCount = 0; // to count failures to move
while (failCount < 2)
{
// if on axis of movement, count as failure and change axis
if ((movingVertically && dy == 0) || (!movingVertically && dx == 0))
{
failCount++;
movingVertically = !movingVertically;
}
// determine axial directions to check
int x = 0, y = 0;
if (movingVertically) y = dy; else x = dx;
// make move along current axis
setLocation(getX()+x, getY()+y);
// do no more if not blocked by wall
if (getOneIntersectingObject(Wall.class) == null) break;
// move back, count as failure and change axis
setLocation(getX()-x, getY()-y);
failCount++;
movingVertically = !movingVertically;
}Just the way I wanted to. Nice! Thanks!
You need to login to post a reply.