为什么我的碰撞检测不能正常工作？

Question

我正在开发广为人知的游戏 Pong，我运行遇到了一些碰撞检测问题：球拍和球大部分时间会发生碰撞，但有时也会发生碰撞出现一个奇怪的问题：未检测到碰撞，因此，球落在球拍后面并且没有改变方向。我无法弄清楚问题隐藏在哪里。我们将不胜感激。

注意： 根据评论进行了编辑。

GamePanel.java

public class GamePanel extends JPanel implements ActionListener, KeyListener {

    Ball ball = new Ball();
    Player player = new Player();

    private void update() {
        checkCollision();
    }

    @Override
    public void actionPerformed(ActionEvent a) {
        update();
    }

    public void checkCollision() {
        Rectangle playerRect = player.bounds();
        Rectangle ballRect = ball.bounds();
        if (playerRect.intersects(ballRect)) {
            if (ball.getyVelocity() < 0) {
                ball.setxVelocity(5);
                ball.setyVelocity(-5);
            } else if (ball.getyVelocity() > 0) {
                ball.setxVelocity(-5);
                ball.setyVelocity(5);
            }
        }
    }

}

Ball.java

public class Ball {

    private final int RADIUS = 15;
    private final int DIAMETER = RADIUS * 2;

    private int x_pos = 250;
    private int y_pos = 250;

    private int xVelocity = -5;
    private int yVelocity = -5;

    public void update() {
        x_pos += xVelocity;
        y_pos += yVelocity;

        if (x_pos <= 0 + RADIUS) {
            xVelocity = 5;
        } else if (x_pos >= Pong.WINDOW_WIDTH - (5 + RADIUS)) {
            xVelocity = -5;
        }

        if (y_pos <= 0 + RADIUS) {
            yVelocity = 5;
        } else if (y_pos >= Pong.WINDOW_HEIGHT - (15 + DIAMETER)) {
            yVelocity = -5;
        }
    }

    public void paint(Graphics g) {
        g.setColor(Color.white);
        g.fillOval(x_pos - RADIUS, y_pos - RADIUS, DIAMETER, DIAMETER);
    }

    public Rectangle bounds() {
        return (new Rectangle(x_pos - RADIUS, y_pos - RADIUS, DIAMETER, DIAMETER));
    }

    public int getxVelocity() {
        return xVelocity;
    }

    public int getyVelocity() {
        return yVelocity;
    }

    public void setxVelocity(int xVelocity) {
        this.xVelocity = xVelocity;
    }

    public void setyVelocity(int yVelocity) {
        this.yVelocity = yVelocity;
    }

}

Player.java

public class Player {

    private final int WIDTH = 15;
    private final int HEIGHT = 150;

    private final int X_POS = 5 + WIDTH / 2;

    private int y_pos = Pong.WINDOW_HEIGHT / 2 - HEIGHT / 2;

    private int yVelocity = 0;

    public void update() {
        y_pos += yVelocity;

        if (y_pos < 0 + HEIGHT / 2) {
            y_pos = 0 + HEIGHT / 2;
        } else if (y_pos > Pong.WINDOW_HEIGHT - 25 - HEIGHT / 2) {
            y_pos = Pong.WINDOW_HEIGHT - 25 - HEIGHT / 2;
        }
    }

    public void paint(Graphics g) {
        g.setColor(Color.white);
        g.fillRect(X_POS, y_pos - HEIGHT / 2, WIDTH, HEIGHT);
    }

    public int getyVelocity() {
        return yVelocity;
    }

    public void setyVelocity(int yVelocity) {
        this.yVelocity = yVelocity;
    }

    public int getY_pos() {
        return y_pos;
    }

    public void setY_pos(int y_pos) {
        this.y_pos = y_pos;
    }

    public int getX_POS() {
        return X_POS;
    }

    public int getWIDTH() {
        return WIDTH;
    }

    public int getHEIGHT() {
        return HEIGHT;
    }

    public Rectangle bounds() {
        return (new Rectangle(X_POS, y_pos - HEIGHT / 2, WIDTH, HEIGHT));
    }

}

Answer 1

在您的 checkCollision 方法中，您必须将 xVelocity 设置回正数。试试这个：

public void checkCollision() {
      Rectangle playerRect = player.bounds();
      Rectangle ballRect = ball.bounds();
      if (playerRect.intersects(ballRect)) {
          if (ball.getyVelocity() < 0) {
            ball.setxVelocity(5);
            ball.setyVelocity(-5);
        } else if (ball.getyVelocity() > 0) {
            ball.setxVelocity(5);
            ball.setyVelocity(5);
        }
    }
}

这样想，如果球向左移动并击中球员，您希望它回到右侧。当它们向右移动时，X 坐标会上升，因此将 xvelocity 设置为负数会导致它继续穿过桨板，就好像它没有碰到它一样。

Answer 2

public void checkCollision() {
    Rectangle playerRect = player.bounds();
    Rectangle ballRect = ball.bounds();
    if (playerRect.intersects(ballRect)) {
        if (ball.getyVelocity() < 0) {
            ball.setxVelocity(5); <-- these should be the same value
            ball.setyVelocity(-5);
        } else if (ball.getyVelocity() > 0) {
            ball.setxVelocity(-5); <-- these should be the same value
            ball.setyVelocity(5);
        }
    }
}

你的问题就出在这里。在 Pong 中，您（玩家）只能将球击向另一侧；如果你在左边，你就会向右击球，反之亦然。因此，在任何碰撞之后，无论传入球的 y 速度如何，球的 x 速度应始终保持相同方向。但是，由于您根据球的 y 速度将 x 速度设置为不同的值，因此其中一种情况会导致球穿过球拍。

为什么我的碰撞检测不能正常工作？

Why is my collision detection not working properly?

java

collision-detection

jpanel

jframe

pong

GamePanel.java

Ball.java

Player.java