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smcgee
smcgee wrote ...

2016/11/30

Remove Objects add Objects

smcgee smcgee

2016/11/30

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import greenfoot.*;  // (World, Actor, GreenfootImage, and Greenfoot)
import java.util.List;
 
/**
 * A rocket that can be controlled by the arrowkeys: up, left, right.
 * The gun is fired by hitting the 'space' key.
 *
 * @author Poul Henriksen
 * @author Michael Kölling
 *
 * @version 2.0
 */
public class Rocket extends Mover
{
    private int gunReloadTime;              // The minimum delay between firing the gun.
    private int reloadDelayCount;           // How long ago we fired the gun the last time.
    private Vector acceleration;            // A vector used to accelerate when using booster.
    private int shotsFired;                 // Number of shots fired.
 
    private GreenfootImage rocket = new GreenfootImage("rocket.png");
    private GreenfootImage rocketWithThrust = new GreenfootImage("rocketWithThrust.png");
 
    /**
     * Initialise this rocket.
     */
    public Rocket()
    {
        gunReloadTime = 20;
        reloadDelayCount = 0;
        acceleration = new Vector(0, 0.3);    // used to accelerate when thrust is on
        increaseSpeed(new Vector(13, 0.3));   // initially slowly drifting
        shotsFired = 0;
    }
 
    /**
     * Do what a rocket's gotta do. (Which is: mostly flying about, and turning,
     * accelerating and shooting when the right keys are pressed.)
     */
    public void act()
    {
        move();
        checkKeys();
        checkCollision();
        reloadDelayCount++;
    }
 
    /**
     * Return the number of shots fired from this rocket.
     */
    public int getShotsFired()
    {
        return shotsFired;
    }
 
    /**
     * Set the time needed for re-loading the rocket's gun. The shorter this time is,
     * the faster the rocket can fire. The (initial) standard time is 20.
     */
    public void setGunReloadTime(int reloadTime)
    {
        gunReloadTime = reloadTime;
    }
 
    /**
     * Check whether we are colliding with an asteroid.
     */
    private void checkCollision()
    {
 
        Asteroid a = (Asteroid) getOneIntersectingObject(Asteroid.class);
        if (a != null)
        {
            getWorld().addObject(new Explosion(), getX(), getY());
            getWorld().removeObject(this);
            getWorld().removeObjects(getWorld().getObjects(Asteroid.class));
        }
    }
 
    /**
     * Check whether there are any key pressed and react to them.
     */
    private void checkKeys()
    {
        ignite(Greenfoot.isKeyDown("up"));
 
        if(Greenfoot.isKeyDown("left")) {
            turn(-5);
        }       
        if(Greenfoot.isKeyDown("right")) {
            turn(5);
        }
        if(Greenfoot.isKeyDown("space")) {
            fire();
        }       
    }
 
    /**
     * Should the rocket be ignited?
     */
    private void ignite(boolean boosterOn)
    {
        if (boosterOn) {
            setImage(rocketWithThrust);
            acceleration.setDirection(getRotation());
            increaseSpeed(acceleration);
        }
        else {
            setImage(rocket);       
        }
    }
 
    /**
     * Fire a bullet if the gun is ready.
     */
    private void fire()
    {
        if (reloadDelayCount >= gunReloadTime) {
            Bullet b = new Bullet(getMovement().copy(), getRotation());
            getWorld().addObject(b, getX(), getY());
            b.move();
            shotsFired++;
            reloadDelayCount = 0;   // time since last shot fired
        }
    }
}
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I am attempting to remove all of the Asteroids from the world once the rocket has been removed. But I keep getting a run time error on my code: getWorld().removeObjects(getWorld().getObjects(Asteroid.class));
 
In addition, I want an image to appear after the World is clear.
smcgee smcgee

2016/11/30

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I am attempting to remove all of the Asteroids from the world once the rocket has been removed. But I keep getting a run time error on my code: getWorld().removeObjects(getWorld().getObjects(Asteroid.class)); In addition, I want an image to appear after the World is clear.
Super_Hippo Super_Hippo

2016/11/30

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Once you remove the object from the world, 'getWorld' will return 'null' and you can't remove objects from 'null'. So you have to remove the asteroids first, then change the background of the world (for example) and then remove the rocket. As an alternative, you can save the reference to the world and then do it in any order you want.
danpost danpost

2016/11/30

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This sounds like a game control issue which should be dealt with by your world (not by a rocket). You could just place the following lines in your World subclass act method:
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if (getObjects(Rocket.class).isEmpty())
{
    removeObjects(getObjects(Asteroid.class));
    setBackground("background2.jpg"); // adjust filename as needed
}
smcgee smcgee

2016/11/30

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dan - excellent - this worked for everyone! smcgee
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