Stopping image movement

Question

okay, so i have my image move straight down along the y axis whenever i click the mouse, my only problem is i don't know how to get it to stop when it hits the bottom of the screen, can someone please help?

    import java.awt.Point;
import org.newdawn.slick.GameContainer;
import org.newdawn.slick.Graphics;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.state.BasicGameState;
import org.newdawn.slick.state.StateBasedGame;

public class Control extends BasicGameState {
    public static final int ID = 1;

    public Methods m = new Methods();
    public Point[] point = new Point[(800 * 600)];

    int pressedX;
    int pressedY;
    int num = 0;
    String Build = "1.1";

    public void init(GameContainer container, StateBasedGame game) throws SlickException{
    }

    public void render(GameContainer container, StateBasedGame game, Graphics g) throws SlickException {
        for (Point p : point) {
            if (p != null) {
                m.drawParticle(p.x, p.y += 1);
            }
        }
        g.drawString("Particle Test", 680, 0);
        g.drawString("Build: " + Build, 680, 15);
        g.drawString("Pixels: " + num, 10, 25);
    }

    public void update(GameContainer container, StateBasedGame game, int delta) {
    }

    public void mousePressed(int button, int x, int y) {
        pressedX = x;
        pressedY = y;
        num = num + 1;
        point[num] = new Point(pressedX, pressedY);
        }

    public int getID() {
        return ID;
    }

}

score 0 · Accepted Answer · answered Oct 08 '12 at 04:57

I'd imagine somewhere you will want to check the x/y pos of the particle before you renderer it and remove it from the array when it's out of bounds...

public void render(GameContainer container, StateBasedGame game, Graphics g) throws SlickException {
    for (int index = 0; index < point.length; index++) {
        Point p = point[index];
        if (p != null) {
            p.y++;
            if (p.y > height) { // You'll need to define height...
                point[index] = null; // Or do something else with it??
            } else {
                m.drawParticle(p.x, p.y);
            }
        }
    }
    g.drawString("Particle Test", 680, 0);
    g.drawString("Build: " + Build, 680, 15);
    g.drawString("Pixels: " + num, 10, 25);
}

You could also do a preemptive check, which would allow you to know what points are at the bottom of the screen...

        if (p != null) {
            if (p.y >= height) { // You'll need to define height...
                // Do something here
            } else {
                p.y++;
                m.drawParticle(p.x, p.y);
            }
        }

thanks, now do you have any idea how i would get it to stop moving down? — user1610541, Oct 08 '12 at 05:35
In second example, if the `p.y` is equal to or greater then the available height, it's y position should never be updated again...Obviously if you remove it from the array (set the array position to null), it not only will never move again, it won't be painted ;) — MadProgrammer, Oct 08 '12 at 05:38
Yes. The second sample will stop updating the y position once p.y >= the available height... — MadProgrammer, Oct 08 '12 at 05:45

Stopping image movement

1 Answers1