Java 小行星球角计算

现在我正在制作经典的小行星游戏。我用箭头键让飞船360度移动。然而，当我试图以这个角度将球射出飞船时，它们只会以45度的增量离开。我想这意味着我在球类课上的数学有问题：

public Ball(double ballAngle){

    angle = ballAngle;

    xRatio = Math.cos((angle + 90) * 3.14 / 180);
    yRatio = Math.sin((angle + 90) * 3.14 / 180);

    xChange = xRatio * speed;
    yChange = yRatio * speed;

}

public void update(){

    x = (int) Math.round(x + xChange);
    y = (int) Math.round(y + yChange);

}

然而，我似乎找不到发生了什么。我试着通过打印值并一步一步地跟踪它们来调试它，但仍然无法解决它。这是我的代码的其余部分，以备您需要查看

主要游戏类别：

package Asteroids;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import java.util.ArrayList;

@SuppressWarnings("serial")
public class Asteroids extends JPanel implements KeyListener{

public final static int BOX_WIDTH = 600;
public final static int BOX_HEIGHT = 600;

public final static int UPDATE_RATE = 300;

public final static double shipSpeed = 1;

ArrayList<Ball> balls = new ArrayList<Ball>();

int i = 0;

int ballCount = 0;

boolean spawn = false;

Ship ship = new Ship(BOX_WIDTH / 2,BOX_HEIGHT / 2);

public Asteroids(){

    //Set window size
    setPreferredSize(new Dimension(BOX_WIDTH,BOX_HEIGHT));

    //Start game thread
    Thread gameThread = new Thread() {

        public void run(){

            while(true){

                ship.update();

                for (int j=0; j<ballCount; j++){

                    balls.get(j).update();

                }

                if(spawn){

                    i++;

                }

                if(i % 100 == 0){

                    balls.add(new Ball(ship.getAngle()));
                    ballCount ++;

                }

                repaint();

                try {Thread.sleep(1000 / UPDATE_RATE);} 
                catch (InterruptedException ex) {}

            }
        }

    };

    gameThread.start();

}


@Override
public void paintComponent(Graphics g) {

    g.setColor(Color.black);

    g.fillRect(0, 0, BOX_WIDTH, BOX_HEIGHT);

    for (int j=0; j<ballCount; j++){

        balls.get(j).draw(g);

    }

    ship.draw(g);

}

public void keyPressed(KeyEvent e){

    if(e.getKeyCode() == KeyEvent.VK_LEFT){

        ship.setSpeed(-shipSpeed);

    }

    if(e.getKeyCode() == KeyEvent.VK_RIGHT){

        ship.setSpeed(shipSpeed);

    }

    if(e.getKeyCode() == KeyEvent.VK_SPACE){

        spawn = true;

    }

}

public void keyReleased(KeyEvent e) {

    if(e.getKeyCode() == KeyEvent.VK_LEFT){

        ship.setSpeed(0);

    }

    if(e.getKeyCode() == KeyEvent.VK_RIGHT){

        ship.setSpeed(0);

    }

    if(e.getKeyCode() == KeyEvent.VK_SPACE){

        spawn = false;

    }

}

public void keyTyped(KeyEvent e) {}

public static void main(String[] args) {

     javax.swing.SwingUtilities.invokeLater(new Runnable() {

            public void run() {

                //Create Frame
                JFrame frame = new JFrame("ASTEROIDS");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                Asteroids asteroids = new Asteroids();
                frame.setContentPane(asteroids); 
                frame.setSize(BOX_WIDTH,BOX_HEIGHT);
                frame.pack();
                frame.addKeyListener(asteroids);
                frame.setVisible(true);

            }

        });

}

public int getBoxHeight(){

    return BOX_HEIGHT;

}

public int getBoxWidth(){

    return BOX_WIDTH;

}

}

---

我怀疑这是一个舍入错误。您将x和y存储为int原语，然后向其中添加双精度，并将其存储回int。如果您将x和y更改为双精度，然后仅在显示位置之前对其进行四舍五入，则不会出现此问题

如果必须阅读数百行代码，没有人会愿意帮助您。请仅包含相关内容或将您的程序分解为再现您的问题的尽可能小的代码。

package Asteroids;

import java.awt.Color;
import java.awt.Graphics;
import java.util.Random;

public class Ship {

Random rng = new Random();

int r = rng.nextInt(256);
int g = rng.nextInt(256);
int b = rng.nextInt(256);

Color color = new Color(r,g,b);

double speed = 0;

double angle = 0;

final static int shipLength = 20;
final static int shipAngle = 40;

static int x;
static int y;

int point1x;
int point2x;
int point3x;

int point1y;
int point2y;
int point3y;

public Ship(int xPos, int yPos){

    x = xPos;
    y = yPos;

    point1x = x;
    point2x = (int) Math.round( x - (Math.tan(shipAngle * 6.28 / 360) * shipLength));
    point3x = (int) Math.round( x + (Math.tan(shipAngle * 6.28 / 360) * shipLength));

    point1y = y - shipLength;
    point2y = y + shipLength;
    point3y = y + shipLength;

}

public void update(){

    angle  = angle + speed;

    if(angle < 0){

        angle = angle + 360;

    }

    else if(angle >= 360){

        angle = angle - 360;

    }

}

public void draw(Graphics g) {

    g.setColor(color);

    point1x = x - (int) Math.round( Math.sin(angle * 6.28 / 360) * shipLength);
    point2x = x + (int) Math.round( Math.sin((angle + shipAngle) * 6.28 / 360) * shipLength);
    point3x = x + (int) Math.round( Math.sin((angle - shipAngle) * 6.28 / 360) * shipLength);

    point1y = y + (int) Math.round( Math.cos(angle * 6.28 / 360) * shipLength);
    point2y = y + (int) Math.round( Math.cos((angle + 180 + shipAngle) * 6.28 / 360) * shipLength);
    point3y = y + (int) Math.round( Math.cos((angle - 180 - shipAngle) *    6.28 / 360) * shipLength);

    int xpoints[] = {point1x, point2x, point3x};
    int ypoints[] = {point1y, point2y, point3y};
    int npoints = 3;

    g.fillPolygon(xpoints, ypoints, npoints);

}

public void setSpeed(double s){

    speed = s;

}

public static int getX(){

    return x;

}

public static int getY(){

    return y;

}

public double getAngle(){

    return angle;

}

}

package Asteroids;

import java.awt.Color;
import java.awt.Graphics;

public class Ball {

int x = Ship.getX();
int y = Ship.getY();

double angle;

double xRatio;
double yRatio;

double xChange;
double yChange;

final static int speed = 1;

final static int diameter = 5;

public Ball(double ballAngle){

    angle = ballAngle;

    xRatio = Math.cos((angle + 90) * 3.14 / 180);
    yRatio = Math.sin((angle + 90) * 3.14 / 180);

    xChange = xRatio * speed;
    yChange = yRatio * speed;

}

public void update(){

    x = (int) Math.round(x + xChange);
    y = (int) Math.round(y + yChange);

}

public void draw(Graphics g) {

    g.setColor(Color.white);

    g.fillOval(x - diameter/2, y - diameter/2, diameter, diameter);

}

}