Question

我想实现一个简单的Java绘画示例，以模拟汽车/拖拉机的行驶路线。为此，我只想在JPanel（这是我的汽车/拖拉机:-）的中间添加一条简单的线。当我使用键盘的上，下，左，右键时，驱动路径应画在面板上。

我能够意识到这一点，但前提是我必须移动面板上的线（意味着我要在面板上移动汽车/拖拉机）。但是我要做的是不移动生产线（汽车/拖拉机）。轿厢/牵引车应始终位于面板中间，但路径应在轿厢后面涂漆。它应该看起来像背景在移动吗？类似于汽车导航系统。

我不确定该如何实现。

我添加了以下图片以详细说明我想要实现的目标：

图片中间的蓝色箭头是汽车/拖拉机。在它的后面，屏幕上绘制了一条黑线。汽车/拖拉机的移动路径在黑色线条后以蓝色绘制。在我的应用程序中，我有GPS坐标系，可用于计算具有x和y坐标的点。有了这些计算出的点，我想绘制移动的汽车/拖拉机的路径。但是汽车/拖拉机应始终位于JPanel的中间。只有路径可以移动和旋转。

示例：

import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;

public class Start {

    public static void main(String[] args)
    {

        JFrame frame = new JFrame("AutoPilot");
        frame.setSize(800,600);

        Stage e1 = new Stage();
        frame.getContentPane().add(e1);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.addKeyListener(new KeyListener() {

            @Override
            public void keyPressed(KeyEvent e)
            {
                switch(e.getKeyCode())

                {
                case KeyEvent.VK_LEFT:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_RIGHT:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_UP:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_DOWN:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_PLUS:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_MINUS:
                    e1.moveLine(e);
                    break;

                case KeyEvent.VK_Z:
                    e1.moveLine(e);
                    break;
                }
            }

            @Override
            public void keyReleased(KeyEvent e) {
                // TODO Auto-generated method stub
            }

            @Override
            public void keyTyped(KeyEvent e) {
                // TODO Auto-generated method stub
            }
        });

        frame.setVisible(true);
    }
}


import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.KeyEvent;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.geom.AffineTransform;
import java.awt.geom.Line2D;
import java.awt.geom.Point2D;
import java.awt.image.BufferedImage;

import javax.swing.JPanel;

public class Stage extends JPanel
{

    int pW = 800;
    int pH = 600;

    double centerX, centerY;
    double x,y,angle, angleLine, xpic,ypic;
    double w = 15;
    double x1,y1,x2,y2,x3,y3;

    BufferedImage bi;

    private boolean gf_rotate;
    private boolean gf_bgSet;
    private boolean gf_rotated;

    public Stage()
    {
        setLayout(null);
        setBounds(0,0,pW,pH);
        setBackground(Color.WHITE);
        centerX = this.getWidth()/2;
        centerY = this.getHeight()/2;

        x = centerX;
        y = centerY;

        xpic = centerX;
        ypic = centerY;

        bi = new BufferedImage(pW, pH, BufferedImage.TYPE_INT_RGB);

        addMouseListener(new MouseListener() {

            @Override
            public void mouseClicked(MouseEvent arg0) {
                System.out.println(arg0.getX() +","+ arg0.getY());  // TODO Auto-generated method stub
            }
            @Override
            public void mouseEntered(MouseEvent arg0) {
                // TODO Auto-generated method stub
            }
            @Override
            public void mouseExited(MouseEvent arg0) {
                // TODO Auto-generated method stub
            }
            @Override
            public void mousePressed(MouseEvent arg0) {
                // TODO Auto-generated method stub
            }
            @Override
            public void mouseReleased(MouseEvent arg0) {
                // TODO Auto-generated method stub
            }
        });
    }

    public void moveLine(KeyEvent e)
    {
        switch(e.getKeyCode())
        {
        case KeyEvent.VK_PLUS:
            angle--;
            angleLine--;

            gf_rotate = true;
            repaint();

            break;

        case KeyEvent.VK_MINUS:
            angle++;
            angleLine++;

            gf_rotate = true;
            repaint();

            break;

        case KeyEvent.VK_LEFT:
            break;

        case KeyEvent.VK_RIGHT:
            break;

        case KeyEvent.VK_UP:
            y--;
            ypic++;

            if (gf_rotate == true)
            {

                gf_rotated = true;
            }

            gf_rotate = false;
            repaint();
            break;

        case KeyEvent.VK_DOWN:
            y++;
            ypic--;

            if (gf_rotate == true)
            {
                gf_rotated = true;
            }
            gf_rotate = false;
            repaint();
            break;

        case KeyEvent.VK_Z:
            repaint();
            break;
        }
    }

    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) bi.createGraphics();
        Graphics2D g2dMain = (Graphics2D) g;

        double _x,_y;

        //Hintergrundfarbe (Bild) setzen
        if (gf_bgSet==false)
        {
            g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
            g2d.setColor(Color.WHITE);
            g2d.fillRect(0, 0, pW, pH);

            g2d.setColor(Color.BLUE);

            Line2D line = new Line2D.Double(x, y, x+100,y);
            g2d.draw(line);

            gf_bgSet=true;
        }

        float[] fa = {1};

        BasicStroke s = new BasicStroke(1, BasicStroke.CAP_SQUARE, BasicStroke.JOIN_ROUND,15,fa,15);

        g2d.setStroke(s);

        _x  =x;
        _y = y;

        if (gf_rotated==true)
        {
            _x=400;
            _y=300;
        }

        Point2D p1 = new Point2D.Double(_x,_y);
        Point2D p2 = new Point2D.Double(p1.getX()+100,p1.getY());
        Line2D line = null;

        if (gf_rotate==true)
        {
            line = new Line2D.Double(p1.getX(), p1.getY(), p2.getX(),p2.getY());
        }
        else
        {
            Point2D p3 =  rotateLine(p1,p2,angleLine);

            line = new Line2D.Double(p1.getX(), p1.getY(), p3.getX(),p3.getY());
        }
        g2d.setColor(new Color(255,80,90,100));


        AffineTransform atLine = null;

        if (gf_rotated == true)
        {

            atLine = new AffineTransform();
            atLine = g2d.getTransform();
            g2d.setColor(Color.GREEN);

            Point2D newP2 = rotateLine(p1,p2,angleLine);

            line = new Line2D.Double(p1.getX()-(centerX-x), p1.getY()-(centerY-y), newP2.getX()-(centerX-x),newP2.getY()-(centerY-y));

        }
        else
        {
            //Rotate line
            atLine = new AffineTransform();
            atLine.translate(x,y);
            if (gf_rotate==true)
            {
                atLine.rotate(Math.toRadians(angle));
            }
            atLine.translate(-x,-y);
        }

        g2d.draw(atLine.createTransformedShape(line));

        g2d.dispose();

        AffineTransform at = new AffineTransform();

        AffineTransform old = g2d.getTransform();

        at.translate(xpic,ypic);

        at.rotate(Math.toRadians(-angle),centerX-xpic,centerY-ypic);

        at.translate(-centerX,-centerY);

        g2dMain.drawImage(bi, at , null);

        g2d.setTransform(old);

        g2dMain.dispose();
    }

    private Point2D rotateLine(Point2D center, Point2D edge, double angle2) {

        double xRot = (int) center.getX() + Math.cos(Math.toRadians(angle2)) * (edge.getX() - center.getX()) - Math.sin(Math.toRadians(angle2)) * (edge.getY() - center.getY());
        double yRot = (int) center.getY() + Math.sin(Math.toRadians(angle2)) * (edge.getX() - center.getX()) + Math.cos(Math.toRadians(angle2)) * (edge.getY() - center.getY());
        return new Point2D.Double(xRot, yRot);
    }
}

Java-涂漆汽车行驶路线

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