当所有其他精灵都移动时，为什么 Carpaint 不移动？

Question

我有一个用于在动画中移动精灵的代码——除了我的一个精灵之外，所有精灵都在移动，我不知道为什么。有人可以解释吗？

我的精灵类：

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.

}

我的精灵不起作用：

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：

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);

}

我预计所有精灵都会移动，但汽车不会移动（参见此处：https ://i.gyazo.com/0219127277d2543735b3a4727e7c7e72.mp4 ）

Answer 1

答案来自@RealSkeptic - 我没有参考xand来粉刷汽车y。新代码：class Carpaint extends SimpleSprite {&nbsp; &nbsp; public Carpaint(float x, float y, float dx, float dy) {&nbsp; &nbsp; &nbsp; &nbsp; super(x, y, dx, dy);&nbsp; &nbsp; }&nbsp; &nbsp; @Override&nbsp; &nbsp; public void draw(Graphics2D g2d){&nbsp; &nbsp; &nbsp; &nbsp; g2d.setColor(Color.pink);&nbsp; &nbsp; &nbsp; &nbsp; g2d.fillRect((int) x, (int) y, 40, 60);&nbsp; &nbsp; &nbsp; &nbsp; g2d.setColor(Color.black);&nbsp; &nbsp; &nbsp; &nbsp; g2d.drawRect((int) x, (int) y, 40, 60);&nbsp; &nbsp; &nbsp; &nbsp; g2d.drawRect((int) x + 10, (int) y + 10, 20, 40);&nbsp; &nbsp; &nbsp; &nbsp; g2d.fillRect((int) x-5, (int) y, 5, 15);&nbsp; &nbsp; &nbsp; &nbsp; g2d.fillRect((int) x + 40, (int) y, 5 , 15);&nbsp; &nbsp; &nbsp; &nbsp; g2d.fillRect((int) x - 5, (int) y + 45, 5, 16);&nbsp; &nbsp; &nbsp; &nbsp; g2d.fillRect((int) x + 40, (int) y + 45, 5, 16);&nbsp; &nbsp; }}