Java 中的打砖块游戏在调用remove() 方法后不传递布尔值

Question

我一直在网上听CS106A的讲座并做作业。我在突破游戏上被困了几天，因为我无法理解它的行为。

基本上，我已经构建了环境，砖块，球，桨，边缘，我可以让球在环境中弹跳。我什至可以让球从砖块上弹开，甚至可以移走砖块。但我无法让球从砖块上弹起并同时移走砖块。

如果您查看我的代码，您会发现我有一个反转球方向的方法。此方法从我的方法中获取一个布尔值，用于检查球是否与环境中的任何对象发生碰撞。如果我不包含“remove()”方法，球将按预期从砖块上弹开。如果我确实包含该方法，球将移走砖块，但不会从它们上反弹。这向我表明代码正在被读取并返回布尔值，但该值没有改变球移动的方向。

/*
 * File: Breakout.java
 * -------------------
 * Name:
 * Section Leader:
 * 
 * This file will eventually implement the game of Breakout.
 */

import java.awt.Color;
import java.awt.event.MouseEvent;

import acm.graphics.GArc;
import acm.graphics.GLine;
import acm.graphics.GObject;
import acm.graphics.GOval;
import acm.graphics.GRect;
import acm.program.GraphicsProgram;
import acm.util.RandomGenerator;


public class Breakout extends GraphicsProgram {

/** Width and height of application window in pixels */
    public static final int APPLICATION_WIDTH = 400;
    public static final int APPLICATION_HEIGHT = 600;

/** Dimensions of game board (usually the same) */
    private static final int WIDTH = APPLICATION_WIDTH;
    private static final int HEIGHT = APPLICATION_HEIGHT;

/** Dimensions of the paddle */
    private static final int PADDLE_WIDTH = 60;
    private static final int PADDLE_HEIGHT = 10;

/** Offset of the paddle up from the bottom */
    private static final int PADDLE_Y_OFFSET = 30;

/** Number of bricks per row */
    private static final int NBRICKS_PER_ROW = 10;

/** Number of rows of bricks */
    private static final int NBRICK_ROWS = 10;

/** Separation between bricks */
    private static final int BRICK_SEP = 4;

/** Width of a brick */
    private static final int BRICK_WIDTH =
      (WIDTH - (NBRICKS_PER_ROW - 1) * BRICK_SEP) / NBRICKS_PER_ROW;

/** Height of a brick */
    private static final int BRICK_HEIGHT = 8;

/** Radius of the ball in pixels */
    private static final int BALL_RADIUS = 10;

/** Offset of the top brick row from the top */
    private static final int BRICK_Y_OFFSET = 70;

/** Number of turns */
/** private static final int NTURNS = 3;*/

/* Method: run() */
/** Runs the Breakout program. */

    public void run() {
        init();
        createBall();
        createSides();
        createBlocks();
        createPaddle();
        addMouseListeners();
        waitForClick();
        while (BALL.getY() <= HEIGHT){
            play();
        }
    }

    public void init(){
        setSize(500,700);
    }

    private void createBlocks(){
        int BRICKS = 0;
        int ROWS = 0;
        while (ROWS != NBRICK_ROWS) {
            while (BRICKS != NBRICKS_PER_ROW){
                GRect BRICK = new GRect (BRICK_WIDTH, BRICK_HEIGHT);
                BRICK.setLocation((BRICKS*(BRICK_SEP + BRICK_WIDTH)+BRICK_SEP), BRICK_Y_OFFSET + (ROWS*(BRICK_HEIGHT + BRICK_SEP)));
                BRICK.setFilled(true);
                if (ROWS == 0 || ROWS == 1){
                    BRICK.setColor(Color.RED);
                    BRICK.setFilled(true);}
                    else if (ROWS == 2 || ROWS == 3) {
                        BRICK.setColor(Color.ORANGE);
                    }   
                    else if (ROWS == 4 || ROWS == 5){
                        BRICK.setColor(Color.YELLOW);
                    }
                    else if (ROWS == 6 || ROWS == 7){
                        BRICK.setColor(Color.GREEN);
                    }
                    else if (ROWS == 8 || ROWS == 9){
                        BRICK.setColor(Color.CYAN);
                    }
                add(BRICK);
                BRICKS++;
            }
            ROWS++;
            BRICKS = 0;
        }
    }

    private void createSides(){
        add(rightSide);
        add(leftSide);
        add(topSide);
        add(bottomSide);
    }

    private void createPaddle(){
        PADDLE.setFilled(true);
        add(PADDLE, WIDTH/2 - (PADDLE_WIDTH/2), HEIGHT - PADDLE_Y_OFFSET);
    }

    private void createBall(){
        BALL.setFilled(true);
        BALL.setLocation(WIDTH/2 - 18, HEIGHT/2);
        add(BALL);
    }

    private void play(){
        /* Add Title Text or Lives or Score */
        ballMovement();
    }

    private void ballMovement(){
        BRICK_COUNT = (NBRICKS_PER_ROW*NBRICK_ROWS);
        while (BRICK_COUNT != 0){
            BALL.move(ballXVelocity(), ballYVelocity());
            pause(5);
            checkXCollision();
            checkYCollision();
        }
    }

    public int ballXVelocity(){
        boolean x = checkXCollision();
        if (x == true){
            BALL_X_VELOCITY = -INITIAL_X_VELOCITY;
            INITIAL_X_VELOCITY = BALL_X_VELOCITY;
        }
        else {BALL_X_VELOCITY = INITIAL_X_VELOCITY;}
        return BALL_X_VELOCITY;
    }

    public int ballYVelocity(){
        boolean y = checkYCollision();
        if (y == true){
            BALL_Y_VELOCITY = -INITIAL_Y_VELOCITY;
            INITIAL_Y_VELOCITY = BALL_Y_VELOCITY;
        }
        else {BALL_Y_VELOCITY = INITIAL_Y_VELOCITY;}
        return BALL_Y_VELOCITY;
    }

    private boolean checkXCollision(){
        double ballX = BALL.getX();
        double ballY = BALL.getY();
        GObject colObjLeft = getElementAt(ballX, ballY - BALL_RADIUS);
        GObject colObjRight = getElementAt(ballX + BALL_RADIUS*2, ballY- BALL_RADIUS);
        if (ballX <= 0 || ballX + (BALL_RADIUS*2) >= APPLICATION_WIDTH){
            return true;
        }
        else if (colObjLeft != null){

            return true;
        }
        else if (colObjRight != null){

            return true;
        }
        else {return false;}
    }

    private boolean checkYCollision(){
        double ballX = BALL.getX();
        double ballY = BALL.getY();
        GObject colObjTop = getElementAt(ballX+ BALL_RADIUS, ballY - 1);
        GObject colObjBot = getElementAt(ballX + BALL_RADIUS, ballY + (BALL_RADIUS*2) + 1);
        if(colObjBot == PADDLE){
            return true;
        } 
        else if (ballY <= 0){
            return true;
            }
        else if (colObjTop != null && colObjTop != BALL){
            remove(colObjTop);
            return true;
        }   
        else if (colObjBot != null && colObjBot != PADDLE && colObjBot != BALL){
            remove(colObjBot);
            return true;
        }
        else {return false;}
    }

    public void mouseMoved(MouseEvent e){
        if (e != null){     
            int x = e.getX();
            PADDLE.setLocation(x - (PADDLE_WIDTH/2), HEIGHT - PADDLE_Y_OFFSET);
        }
    }

    /*public void paddleLocation(dx,dy);*/
        /*int x = */

    public GRect PADDLE = new GRect(PADDLE_WIDTH, PADDLE_HEIGHT);
    private GArc BALL = new GArc(BALL_RADIUS*2, BALL_RADIUS*2, 0,360);
    /*private GOval BALL = new GOval(BALL_RADIUS*2, BALL_RADIUS*2);*/
    private int BRICK_COUNT;
    private int BALL_Y_VELOCITY;
    private int BALL_X_VELOCITY;
    private int INITIAL_Y_VELOCITY = 1;
    private RandomGenerator rgen = RandomGenerator.getInstance();
    private int INITIAL_X_VELOCITY = rgen.nextInt(2);
    private GLine rightSide = new GLine (WIDTH, 0, WIDTH, HEIGHT );
    private GLine leftSide = new GLine (0, 0, 0, HEIGHT);
    private GLine topSide = new GLine (0, 0, WIDTH, 0);
    private GLine bottomSide = new GLine (0, HEIGHT, WIDTH, HEIGHT);
}

Answer 1

看来您对 checkXCollision 和 checkYCollision 的额外调用是问题所在。

您可以在 ballMovement 中直接调用它们，并且每个函数也会在 Velocity 方法内部调用。

要获取 Ball.move 的参数，您可以调用 Velocity 方法，该方法会检查碰撞并移除砖块。但是，在移动球之后，您将立即检查碰撞并再次移除。因此，当 ballMovement 下次运行时，砖块已经被移除，并且 Velocity 方法内的碰撞检测不起作用。

由于您没有对 ballMovement 中的碰撞返回值执行任何操作，因此您可能不需要它们。

Answer 2

欢迎来到SO，很好的第一个问题。

while (BRICK_COUNT != 0){
     BALL.move(ballXVelocity(), ballYVelocity());
     pause(5);
     checkXCollision();
     checkYCollision();
}

我认为错误在于在主循环中调用 check*Collision() 和在 ball*Velocity() 方法中调用 。

如果在 ball*Velocity() 方法之一中发现碰撞，则砖块将被移除，方向会反转，并且看起来不错。

但是，如果在直接调用 check*Collision() 时发现碰撞，则无法反转方向。

但恐怕修复不仅仅是删除这两行。 （但是试一试。:)当球在 X 和 Y 的角落碰撞时会发生什么？我认为事实上，您正在两个不同的函数中检查球速度，可能会在两个不同的函数中改变方向，并且不会在“它们之间”传递知识，因此当球击中时，您的碰撞代码角不正确。 （checkXCollision()，通过 ballXVelocity() 调用，可能会移除通过 ballYVelocity()< 调用 checkYCollision() 的砖块/code>，需要确定是否需要改变方向。）

您可能需要重写函数来同时计算 X 和 Y 碰撞，这样您就可以移除一两个砖块根据需要。

我希望这有帮助。