I am attempting to add directional gravity to object by using the left and right arrow keys. can some one explain what i need to add or if im doing anything wrong?
public class Body extends SmoothMover
{
private static final double GRAVITY = 7.8;
private static final Color defaultColor = new Color(255, 216, 0);
private double mass;
private int size;
/**
* Construct a Body with default size, mass, movement and color.
*/
public Body()
{
this (20, 300, new Vector(0, 0.0), defaultColor);
}
/**
* Construct a Body with a specified size, mass, movement and color.
*/
public Body(int size, double mass, Vector movement, Color color)
{
this.mass = mass;
this.size = size;
addForce(movement);
GreenfootImage image = new GreenfootImage (size, size);
image.setColor (color);
image.fillOval (0, 0, size-1, size-1);
setImage (image);
}
/**
* Act. That is: apply the gravitation forces from
* all other bodies around, and then move.
*/
public void act()
{
applyForces();
move();
bounceAtEdge();
control();
}
/**
* Check whether we have hit the edge of the universe. If so, bounce off it.
*/
private void bounceAtEdge()
{
if (getX() == 0 || getX() == getWorld().getWidth()-1) {
setLocation((double)getX(), (double)getY());
getMovement().revertHorizontal();
accelerate(0.9);
changeColor();
}
else if (getY() == 0 || getY() == getWorld().getHeight()-1) {
setLocation((double)getX(), (double)getY());
getMovement().revertVertical();
accelerate(0.9);
changeColor();
}
}
/**
* Apply the forces of gravity from all other celestial bodies in this universe.
*/
private void applyForces()
{
List<Body> bodies = (List<Body>) getWorld().getObjects(Body.class);
for (Body body : bodies)
{
if (body != this)
{
applyGravity (body);
}
}
// ensure that we don't get too fast: If the current speed is very fast, decelerate a bit.
if (getSpeed() > 5)
{
accelerate (0.9); // acceleration with factor < 1 is actually slowing down.
}
}
/**
* Apply the gravity force of a given body to this one.
*/
private void applyGravity(Body other)
{
double dx = other.getExactX() - this.getExactX();
double dy = other.getExactY() - this.getExactY();
Vector force = new Vector (dx, dy);
double distance = Math.sqrt (dx*dx + dy*dy);
double strength = GRAVITY * this.mass * other.mass / (distance * distance);
double acceleration = strength / this.mass;
force.setLength (acceleration);
addForce (force);
}
/**
* Return the mass of this body.
*/
public double getMass()
{
return mass;
}
public void control()
{
Actor obstacle = getOneIntersectingObject(Obstacle.class);
List<Body> bodies = (List<Body>) getWorld().getObjects(Body.class);
if (Greenfoot.isKeyDown("left"))
{
for (Body body : bodies)
{
if (body != this)
{
applyGravity (body);
}
}
}
if (Greenfoot.isKeyDown("right"))
{
for (Body body : bodies)
{
if (body != this)
{
applyGravity (body);
}
}
}
if (obstacle != null)
{
changeColor();
}
}
private void changeColor()
{
int x = Greenfoot.getRandomNumber(255);
int y = Greenfoot.getRandomNumber(255);
int z = Greenfoot.getRandomNumber(255);
GreenfootImage image = new GreenfootImage (size, size);
image.setColor (new Color(x,y,z));
image.fillOval (0, 0, size-1, size-1);
setImage (image);
}
}
