Java 2D 旋转和全局坐标？

Question

我正在制作一个简单的游戏，其中有一个物体(带有矩形桶的正方形)朝向鼠标。旋转部分工作得很好，但我希望当沿 y 轴按下按钮时对象会移动，但直接向上，而不是相对于其旋转。现在，当按下按钮时，对象会沿其面向的方向向前移动。无论对象处于哪个方向，如何将其直接沿 y 轴移动？代码如下:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class RotationTestMain extends JFrame implements MouseMotionListener, KeyListener{

    public static final long serialVersionUID = 666L;

    public static final int SIZE = 50;

    double xComponent;
    double yComponent;

    Image dbImage;
    Graphics dbg;

    int x;
    int y;
    int centerX;
    int centerY;

    JPanel area;

    public RotationTestMain(){
        area = new JPanel();
        area.addMouseMotionListener(this);
        addKeyListener(this);

        x = 487;
        y = 359;

        centerX = x + SIZE/2;
        centerY = y + SIZE/2;

        add(area);

        setSize(1024,768);
        setLocationRelativeTo(null);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    @Override
    public void paint(Graphics g){
        dbImage = createImage(getWidth(), getHeight());
        dbg = dbImage.getGraphics();
        Graphics2D g2d = (Graphics2D) dbg;
        draw(g2d);
        g.drawImage(dbImage, 0, 0, this);
    }

    public void draw(Graphics2D g2d){
        g2d.setColor(Color.BLACK);
        g2d.rotate(calculateRotation(), centerX, centerY);
        g2d.fillRect(x, y, SIZE, SIZE);
        g2d.fillRect(centerX-5,y-20,10,25);
        repaint();
    }

    public double calculateRotation(){
        double rot;
        if(yComponent >= 0){
            rot = 3 * Math.PI - Math.atan(xComponent/yComponent);
        }else {
            rot = 2 * Math.PI - Math.atan(xComponent/yComponent);
        }
        return rot;
    }

    public static void main(String[] args) {
        new RotationTestMain();
    }

    @Override
    public void mouseDragged(MouseEvent m) {
        centerX = x + SIZE/2;
        centerY = y + SIZE/2;
        xComponent = m.getX() - centerX;
        yComponent = m.getY() - centerY;
    }

    @Override
    public void mouseMoved(MouseEvent m) {
        centerX = x + SIZE/2;
        centerY = y + SIZE/2;
        xComponent = m.getX() - centerX;
        yComponent = m.getY() - centerY;
    }

    @Override
    public void keyPressed(KeyEvent arg0) {
        //TODO FIX THE MOVING PROBLEM
        this.y -= 3;
    }

    @Override
    public void keyReleased(KeyEvent arg0) {
    }

    @Override
    public void keyTyped(KeyEvent arg0) {
    }
}

非常感谢您的帮助!!

Answer 1

我认为问题出在这一行 g2d.rotate(calculateRotation(), centerX, centerY);

你不是在旋转物体，而是在旋转整个g2d。因此，x、y 轴也会旋转，因为它们是 g2d 的一部分。

所以当你这样做时。y -= 3;你确实是沿着 y 轴移动，但是 y 轴已经旋转了。

我建议找到一种方法来旋转对象而不是整个 g2d。