整數會調用一個類，但不會調用另一個類？

Question

我正試圖讓游戲“Snake”，但我卻被卡在了尾巴上。 現在，我只是想讓第一個尾部塊具有與頭部相同的坐標。 這就是我所擁有的。 對於主要類：

public class Game extends JPanel implements ActionListener {
Snake p;
RandomDot r;
Trail trail; 
Point w;
Image img;
Timer time;
int t=75;
int score = 0;
int count = 0;
int x, y;


boolean lost = false;

public Game(){
    p = new Snake();
    r = new RandomDot();
    trail = new Trail();
    w = new Point();
    addKeyListener(new AL());
    setFocusable(true);
    ImageIcon i = new ImageIcon("C:/Matt's stuff/background.png");
    img = i.getImage();
    time = new Timer(t, this);
    time.start();
} 

@Override
public void actionPerformed(ActionEvent e)
{
    p.move();
    p.moveup();
    w.points();
    trail.getFirstDot();
    trail.findCoords();
    if (score>=1)
    {
    trail.getFirstDot();
    }
    if (lost==true)
    {
        score++;
        r.getRandom();
        lost = false;
    }
    repaint();
    checkCollisions();
}


public int score()
{
    return score;
}

public boolean getLost()
{
    return lost;
}

public void checkCollisions()
{
    Rectangle r1 = r.getBounds();
    Rectangle r2 = p.getBounds();
    if (r1.intersects(r2))
    {
        lost = true;
    }
}

@Override
public void paint(Graphics g)
{
        super.paint(g);
                    Graphics2D g2d = (Graphics2D) g;
                    g2d.drawImage(img, 0, 0, null);
                    g2d.drawImage(p.getImage(), p.getX(), p.getY(), null);
                    g2d.drawImage(r.getImage2(), r.getX2(), r.getY2(), null);
                    if (score>=1)
                    {
                        g2d.drawImage(trail.getImage(), trail.getX(), trail.getY(),       null);
                    }
                    System.out.println(score + "00");
}

private class AL extends KeyAdapter{
    @Override
    public void keyReleased(KeyEvent e)
    {
        p.keyReleased(e);
    }
    @Override
    public void keyPressed(KeyEvent e)
    {
        p.keyPressed(e);
    }
}

}

對於Snake的頭類：

public class Snake {
Integer x = 480, y = 280, dx = 0, dy = 0, h, m;
boolean dead = false;
boolean didmove = false;
Image still;
RandomDot r;
Game g;
Trail t;

public Snake(){
    ImageIcon i = new ImageIcon("C:/Matt's Stuff/snake.png");
    still = i.getImage();
}

public Rectangle getBounds(){
    return new Rectangle(x,y, 10, 10);
} 


public void move(){ 
    x = x + dx;
    h = x;
    didmove = true;
    if (x>=990||x<=5){
    dead = true;
    x = 480;
    y = 280;
    dx = 0;
    dy = 0;
    didmove = false;
    }
} 

public void moveup(){
    y = y + dy;
    m = y;
    didmove = true;
    if (y>=590||y<=0){
    dead = true;
    x = 480;
    y = 280;
    dx = 0;
    dy = 0;
    didmove = false;
    }
}

public Integer getX(){
return x;
}

public Integer getY(){
return y;
}

public Image getImage(){
return still;
}
public boolean getBoolean(){
return dead;
}

public boolean didmove(){
return didmove;
}

public void keyPressed(KeyEvent e){
int key = e.getKeyCode();

if (key == KeyEvent.VK_LEFT){
     if (dead == false){
        dx = -10;
        dy = 0;
    } else {
        x = 480;
        y = 280;
        dx = 0;
        dy = 0;
    }
}

if (key == KeyEvent.VK_RIGHT){
    if (dead == false){
        dx = 10;
        dy = 0;
    } else {
        x = 480;
        y = 280;
        dx = 0;
        dy = 0;
    }
}

if (key == KeyEvent.VK_UP){
    if (dead == false){
        dy = -10;
        dx = 0;
    }else {
        x = 480;
        y = 280;
        dx = 0;
        dy = 0;
    }
}

if (key == KeyEvent.VK_DOWN){
    if (dead == false){
        dy = 10;
        dx = 0;
    }else {
        x = 480;
        y = 280;
        dx = 0;
        dy = 0;
    }
}
}

public void keyReleased(KeyEvent e){
int key = e.getKeyCode();



}

}

最后，尾巴：

public class Trail {
Image still;
Integer x = 500, y = 500, dx, dy, dx2, dy2;
Game g;
Snake p;
Point d;
int count=0;


boolean visible = false;
public Trail(){
    ImageIcon i = new ImageIcon("C:/Matt's Stuff/Dot.png");
    still = i.getImage();
    p = new Snake();
    d = new Point();
}

public void getFirstDot(){
    visible = true;
}

public void findCoords(){
    if (visible == true)
    { 
        x = p.getX();
        y = p.getY();
    }
}

public Integer getX(){
    return x;
}

public Integer getY(){
    return y;
}

public Image getImage(){
    return still;
}
}

現在我的問題是這樣的：尾部類中的p.getX()和p.getY()不起作用！ 尾座剛剛坐在蛇頭的起點！ 我不知道發生了什么，我的研究似乎都沒有幫助！ 請幫幫我？ 為什么p.getX()和p.getY()將在主Game類中起作用，但不會在Tail中起作用？ 先感謝您！

Answer 1

你正在你的Trail構造函數中創建一個new Snake() ，然后引用那個 Snake而不是Game知道的那個。 您應該傳入對構造函數的引用，而不是創建新的 Snake ，以便調用實際更新的對象的方法：

// In the Trail class
public Trail(Snake s) {
    p = s;
    // other stuff
}

// In the Game class:
trail = new Trail(p);
// ...

現在當你調用p.getX()等等時，你實際上會指向正確的Snake ，所以你應該看到你的位置正確更新。

Answer 2

您應該將現有Snake對象的引用傳遞給Trail構造函數以使其工作。 例如在Game類中，您的代碼應該是這樣的：

public Game(){
    p = new Snake();
    r = new RandomDot();
    trail = new Trail(p);//Pass the reference of Snake so that you get all information w.r.t the current Snake in consideration
    w = new Point();
    addKeyListener(new AL());
    setFocusable(true);
    ImageIcon i = new ImageIcon("C:/Matt's stuff/background.png");
    img = i.getImage();
    time = new Timer(t, this);
    time.start();
} 

並更改Trail構造函數如下：

public Trail(Snake p){
    ImageIcon i = new ImageIcon("C:/Matt's Stuff/Dot.png");
    still = i.getImage();
    this.p = p;
    d = new Point();
}