我正在研究一个采用船舶对象并移动它的程序。我遇到的麻烦是，如果它越过一侧，那么它应该在另一侧回绕。
任何帮助都会很棒：）
这是我的船类：移动方法是我需要帮助的。我的代码不起作用：/
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import junit.framework.TestCase;
public class Ship {
private BufferedImage _image;
private static final int WIDTH = 50;
private Point location;
private Vector speed = new Vector();
private double facing;
/**
* Generate ship at the given starting location and currently stopped
*
* @param starting
* location to copy for this ship
*/
public Ship(Point starting) {
try {
// Use the RunConfigurations >> Arguments > Working Directory tab so
// that this works. Don't just place the nave.png file in the bin
// directory!
_image = ImageIO.read(new File("nave.png"));
} catch (IOException e) {
System.err.println("Cannot find ship _image: " + e.getMessage());
}
location = starting.clone();
facing = Math.PI;
}
public void accelerate(double force) {
// TODO change the speed (velocity, really) by force in the direction
// the ship is facing.
// add a vector of appropriate magnitude by the facing direction
Vector acc = new Vector(facing);
acc = acc.scale(force);
speed = speed.add(acc);
}
public void rotate(double angle) {
// TODO change the direction the ship is facing. Can accept any angle
// as a parameter but should store it as in [0,2*pi)
while (angle <= 0.0f) {
angle += (Math.PI * 2);
}
while (angle >= Math.PI) {
angle -= (Math.PI * 2);
}
facing += angle;
}
public void move(Dimension bounds) {
// TODO Move the ship its speed. The ship should wrap around
// within its box. (Hint: move the ship by the size of the
// bounding area to wrap it around; you may need to do this
// more than once if the ship is moving fast enough.)
location = speed.move(location);
while (location.getX() > bounds.width) {
Vector v = new Vector(location.getX() - WIDTH);
location = v.move(location);
}
while (location.getX() < -WIDTH) {
Vector v = new Vector(location.getX() + WIDTH);
location = v.move(location);
}
while (location.getY() > bounds.height) {
Vector v = new Vector(location.getY() - WIDTH);
location = v.move(location);
}
while (location.getY() < -WIDTH) {
Vector v = new Vector(location.y() + WIDTH);
location = v.move(location);
}
}
public void draw(Graphics g2d) {
double locationX = _image.getWidth() / 2;
double locationY = _image.getHeight() / 2;
AffineTransform tx = AffineTransform.getRotateInstance(facing,
locationX, locationY);
AffineTransformOp op = new AffineTransformOp(tx,
AffineTransformOp.TYPE_BILINEAR);
// Drawing the rotated image at the required drawing locations
// Code for rotating adapted from StackOverflow.
g2d.drawImage(op.filter(_image, null), location.getX(),
location.getY(), null);
}
这是我的矢量类：所有这些代码都有效：）
public class Vector {
private final double _dx, _dy;
public Vector() {
_dy = 0.0;
_dx = 0.0;
}
public Vector(double x, double y) {
_dx = x;
_dy = y;
}
public Vector(Point a, Point b) {
_dx = b.x() - a.x();
_dy = b.y() - a.y();
}
public Vector(double angle) {
_dx = Math.cos(angle);
_dy = Math.sin(angle);
}
public double dx() {
return _dx;
}
public double dy() {
return _dy;
}
public Point move(Point b) {
double x = b.x();
double y = b.y();
x += _dx;
y += _dy;
return new Point(x, y);
}
public Vector add(Vector a) {
double x = (a._dx + _dx);
double y = (a._dy + _dy);
return new Vector(x, y);
}
public Vector scale(double s) {
double x = _dx * s;
double y = _dy * s;
return new Vector(x, y);
}
public double magnitude() {
double x = Math.pow(_dx, 2);
double y = Math.pow(_dy, 2);
return Math.sqrt(x + y);
}
public Vector normalize() {
double x = _dx / magnitude();
double y = _dy / magnitude();
return new Vector(x, y);
}
public Vector rotate(double rads) {
double theta = angle();
theta += rads;
return new Vector(theta);
}
public double angle() {
double alpha = Math.acos(dx() / magnitude());
if (dy() < 0)
alpha = Math.PI - alpha;
return alpha;
}
@Override
public String toString() {
String vector = "[" + _dx + "," + _dy + "]";
return vector;
}
@Override
public boolean equals(Object obj) {
if (obj instanceof Vector) {
Vector vector = (Vector) obj;
if ((Math.abs(_dx - vector._dx) <= (1 / 10000000000f))
&& (Math.abs(_dy - vector._dy) <= (1 / 10000000000f)))
return true;
else
return false;
} else
return false;
}
@Override
public int hashCode() {
return (int) Math.round((angle() * 180) / Math.PI);
}
}
答案 0 :(得分：2)
扩展使用modulo的建议，你可以按照以下方式使用它来轻松环绕而不用循环：
// Assuming move is called for each time frame
// We can update the location of ship using modulo when it exceeds the bounds
public void move(Dimension bounds) {
// TODO Move the ship its speed. The ship should wrap around
// within its box. (Hint: move the ship by the size of the
// bounding area to wrap it around; you may need to do this
// more than once if the ship is moving fast enough.)
location = speed.move(location);
if (location.getX() > bounds.width) {
location.setLocation(location.getX() % bounds.width), location.getY());
}
else if (location.getX() < 0) {
location.setLocation(bounds.width - location.getX(), location.getY());
}
if (location.getY() > bounds.height) {
location.setLocation(location.getX(), location.getY() % bounds.height);
}
else if (location.getY() < 0) {
location.setLocation(location.getX(), bounds.height - location.getY());
}
}
你已经提供了很多代码，所以我可能已经错过了你为什么需要这样做，而不是创建一个新的delta Vector来移动位置，你也可以确定船应该是新的包裹位置按照setLocation方法设置它。
我希望这会有所帮助。