java为什么当所有其他精灵移动时，Carpaint不移动？

Question

我有一个在动画中移动精灵的代码——除了我的一个精灵外，其他所有精灵都会移动，我不知道为什么。有人能解释一下吗

我的精灵课：

abstract class SimpleSprite {
   // basic x,y movement,keeps a master list of Sprites
   public static final ArrayList<SimpleSprite> sprites = new ArrayList<SimpleSprite>();
   float x, y, dx, dy; // position and velocity (pixels/TIMER_MSEC)
   public SimpleSprite(float x, float y, float dx, float dy) {
      // initial position and velocity
      this.x = x;
      this.y = y;
      this.dx = dx;
      this.dy = dy;
      sprites.add(this);
   }
   public void update() { // update position and velocity every n milliSec
      // default - just move at constant velocity
      x += dx; // velocity in x direction
      y += dy; // velocity in y direction
   }
   abstract public void draw(Graphics2D g2d); 
      // just draw at current position, no updating.
}

我的雪碧坏了：

class Carpaint extends SimpleSprite {
    public Carpaint(float x, float y, float dx, float dy) {
        super(x, y, dx, dy);
    }
    @Override
    public void draw(Graphics2D g2d){
        g2d.setColor(Color.pink);
        g2d.fillRect(50, 50, 40, 60);
        g2d.setColor(Color.black);
        g2d.drawRect(50, 50, 40, 60);
        g2d.drawRect(60, 60, 20, 40);
        g2d.fillRect(45, 50, 5, 15);
        g2d.fillRect(90, 50, 5 , 15);
        g2d.fillRect(45, 95, 5, 16);
        g2d.fillRect(90, 95, 5, 16);
    }
}

我的主要意见是：

public static void main(String[] args) {
    // create and display the animation in a JFrame
    final JFrame frame = new JFrame("Animation 2 (close window to exit)");
    Animation2 animationPanel = new Animation2(600, 500);
    frame.add(animationPanel);
    frame.pack();
    frame.setLocationRelativeTo(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
    // add some sprites...
    new Square(0, 0, 3, 2, 40);
    new Ball(500, 0, -3, 3, 20);
    new Ball(0, 500, 2, -5, 30);
    new Carpaint(100, 100, 20, -6);
}

我希望所有的精灵都能移动，但汽车却不能（参见此处：https://i.gyazo.com/0219127277d2543735b3a4727e7c7e72.mp4）

Answer 1

答案来自@realpoinsist——我并不是在用x和y来粉刷汽车。 新代码：

class Carpaint extends SimpleSprite {
    public Carpaint(float x, float y, float dx, float dy) {
        super(x, y, dx, dy);
    }
    @Override
    public void draw(Graphics2D g2d){
        g2d.setColor(Color.pink);
        g2d.fillRect((int) x, (int) y, 40, 60);
        g2d.setColor(Color.black);
        g2d.drawRect((int) x, (int) y, 40, 60);
        g2d.drawRect((int) x + 10, (int) y + 10, 20, 40);
        g2d.fillRect((int) x-5, (int) y, 5, 15);
        g2d.fillRect((int) x + 40, (int) y, 5 , 15);
        g2d.fillRect((int) x - 5, (int) y + 45, 5, 16);
        g2d.fillRect((int) x + 40, (int) y + 45, 5, 16);
    }
}