Java 编程、突破游戏球物理未按预期运行

Question

我正在学习 java 本书 "The Art and Science of Java: An Introduction to Computer Science"。练习程序之一是创建 Breakout 游戏的简单克隆。

我目前可以加载游戏，但球的物理特性存在问题。我正在使用最简单的物理学，但看不出为什么它不起作用。

当球撞到墙上时，它会正常反弹，但当它撞到球拍或砖块时，它不会反弹。我在碰撞检测中使用相同的代码来改变我在墙壁上使用的方向。检测到碰撞，我添加了一个 println 并观察了控制台，因为它经历了碰撞事件，但没有发生方向变化。

package chapter10;

/* 
 * This program creates a clone of the classic Breakout Game,
 * where a player bounces a ball with a paddle to "break" bricks 
 * along the top of the screen.
 * 
 * Controls: Left: left button, Right: right button
 */

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.RepaintManager;
import javax.swing.Timer;

import acm.program.*;
import acm.graphics.*;

public class BreakoutClone extends GraphicsProgram {

/* components */
private GRect paddle;
private GRect brick;
private GOval ball;

/* static variables */

private static final double PADDLE_HEIGHT = 5;
private static final double BALL_SPEED = 2;
private static final double PADDLE_SPEED = 2;
private static final double ROWS_BRICKS = 6;
private static final double COLUMNS_BRICKS = 10;
private static final double TOP_GAP = 50;

/* variables */

private int numTurns = 3;
private double paddleWidth = 50;
private int dx = 2;
private int dy = 2;

public void init() {
    setSize(700, 600);

    paddle = new GRect(0, getHeight() - 30, paddleWidth, PADDLE_HEIGHT);
    paddle.setFilled(true);
    add(paddle);

    addBricks();

    ball = new GOval(getWidth() / 2, 175, 5, 5);
    ball.setFilled(true);
    add(ball);
}

public void run() {
    animateBall();
    // TODO animate paddle
}

public void addBricks() {
    double gap = 20;
    double brickWidth = getWidth() / COLUMNS_BRICKS;
    for (int r = 0; r < ROWS_BRICKS; r++) {
        for (int b = 0; b < COLUMNS_BRICKS; b++) {
            brick = new GRect(b * brickWidth, gap * r + TOP_GAP,
                    brickWidth, 10);
            brick.setFilled(true);
            add(brick);
        }
    }
}

public void endGame() {
    // TODO write end game method
}

public void animateBall() {

    while (numTurns > 0) {

        ball.move(dx, dy);
        pause(15);

        /* Look for Object Collision */
        GObject topRightObject = getElementAt(ball.getX() + 5, ball.getY());
        GObject topLeftObject = getElementAt(ball.getX(), ball.getY());
        GObject botRightObject = getElementAt(ball.getX() + 5,
                ball.getY() + 5);
        GObject botLeftObject = getElementAt(ball.getX(), ball.getY() + 5);

        /* Bounce off walls */

        if ((ball.getX() >= getWidth() - 5) || ball.getX() <= 0) {
            dx = -dx;
        }
        if (ball.getY() <= 0) {
            dy = -dy;
        }
        if ((ball.getY() >= getHeight() - 5)) {
            dy = -dy;
            // numTurns--;
            // if (numTurns == 0) {
            // endGame();
            // } else {
            // run();
            // }
        }

        /* Bounce off objects, remove bricks */

        if (topRightObject != null) {
            dy = -dy;
            hasCollided(topRightObject);
        }
        if (topLeftObject != null) {
            dy = -dy;
            hasCollided(topLeftObject);
        }
        if (botRightObject != null) {
            dy = -dy;
            hasCollided(botRightObject);
        }
        if (botLeftObject != null) {
            dy = -dy;
            hasCollided(botLeftObject);
        }
    }
}

private void hasCollided(GObject obj) {
    if (obj.equals(paddle)) {
        System.out.println("detecting paddle");

    } else {
        System.out.println("detecting brick");

        remove(obj);
    }
}
}

Answer 1

在球击中球拍时反转方向的部分周围添加一个 if(dy<0)（假设负数 dy 表示球朝向球拍）。这消除了你的方向被改变的可能性，但每次碰撞不止一次

Java 编程、突破游戏球物理未按预期运行

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