java - 斯坦福大学 cs106a - 突破练习

Question

我正在尝试通过在线 cs106a 类(class)来学习 java。目前，我已经达到了突破性的锻炼规模，但遇到了一些错误问题

我还没有完全完成，但我想在继续之前先解决这些问题。

问题1:

当球与砖 block 碰撞时，它们似乎并不总是从 Canvas 上移除。有时，砖 block 会在第二次碰撞时被移除。但有一排(黄色砖 block )对球碰撞完全没有反应。

问题2:

我的桨可以通过拖动鼠标来移动。唯一的问题是。砖 block 也可以像桨一样移动。

我知道这与这段代码有关

gobj = getElementAt(lastX, lastY);

如果我把它完全移除，砖 block 就不再可移动了。这很好。但我还是无论我在何处单击并拖动，都能够移动桨。

有人可以给我提示，以便我纠正错误吗？

下面是我的代码。谢谢

   /*  
 * File: Breakout.java 
 * ------------------- 
 * This file will eventually implement the game of Breakout. 
 */
import acm.graphics.*;
import acm.program.*;
import acm.util.*;
import java.applet.*;
import java.awt.*;
import java.awt.event.*;

import org.omg.CORBA.PUBLIC_MEMBER;

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 = 8;
    /** 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;


    private static final int DELAY = 50;
    private static final double X_START = WIDTH / 2;
    private static final double Y_START = 450;

    public void run() {
        world();
        play();
    }

    private void ball() {

        ball = new GOval(X_START, Y_START, BALL_RADIUS, BALL_RADIUS);
        ball.setFillColor(Color.BLACK);
        ball.setFilled(true);
        add(ball);

    }

    private void paddle() {

        paddle = new GRect(100, 500, PADDLE_WIDTH, PADDLE_HEIGHT);
        paddle.setColor(Color.BLACK);
        paddle.setFilled(true);
        add(paddle);
    }


    private void brick(int x, int y, Color c) {

        GRect brick = new GRect(x, y, BRICK_WIDTH, BRICK_HEIGHT);
        brick.setColor(getBackground());
        brick.setFillColor(c);
        brick.setFilled(true);
        add(brick);

    }

    private void brickRow(int x, int y, Color c) {
        x = BRICK_SEP / 2;
        y += BRICK_Y_OFFSET;
        for (int i = 0; i < NBRICKS_PER_ROW; i++) {
            brick(x, y, c);
            x += BRICK_WIDTH + BRICK_SEP;
        }

    }


private void world() {

        //initialize x and y position for the rows of bricks
        int x = 0;
        int y = 0;
        // set starting color for first row
        Color c = Color.red;

        paddle();

        //create 2 rows of bricks and switch colors
        for (int i = 0; i < NBRICK_ROWS; i++) {
            if (i <= 1) {
                c = Color.ORANGE;

            } else if (i > 1 && i <= 3) {
                c = Color.YELLOW;

            } else if (i > 3 && i <= 5) {
                c = Color.GREEN;

            } else if (i > 5 && i <= 7) {
                c = Color.CYAN;
            }

            brickRow(x, y, c);
            y += BRICK_HEIGHT + BRICK_SEP;
        }

    }



    private void moveBall() {
        ball.move(xVel, yVel);

    }


    public void mousePressed(MouseEvent e) {

        lastX = e.getX();
        lastY = e.getY();
        gobj = getElementAt(lastX, lastY);

    }

    public void mouseDragged(MouseEvent e) {
        if (paddle != null) {
            paddle.move(e.getX() - lastX, getY());
            lastX = e.getX();
            lastY = e.getY();
        }

        //constrain paddle movement
        if (paddle.getX() < 0){
            paddle.setLocation(0, 500);
        }else if (paddle.getX()+BRICK_WIDTH > WIDTH ){
            paddle.setLocation(WIDTH-BRICK_WIDTH, 500);
        }


    }

    private void checkForCollision() {

        // ball collission with walls
        if (ball.getY() > getHeight() - BALL_RADIUS
                || ball.getY() < 0 + BALL_RADIUS) {
            yVel = -yVel;
        } else if (ball.getX() > getWidth() - BALL_RADIUS
                || ball.getX() < 1 + BALL_RADIUS) {
            xVel = -xVel;

            // ball collission with paddle
        } else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
                + BALL_RADIUS) == paddle) {
            yVel = -yVel;

            // check for collision with bricks to remove them but ignore collision with paddle
        } else if (getElementAt(ball.getX(), ball.getY()) != null
                && getElementAt(ball.getX(), ball.getY()) != paddle) {
            remove(getCollidingObject(ball.getX(), ball.getY()));
            yVel = -yVel;

        } else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
                + BALL_RADIUS) != null
                && getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
                        + BALL_RADIUS) != paddle) {
            remove(getCollidingObject(ball.getX() + BALL_RADIUS, ball.getY()
                    + BALL_RADIUS));
            yVel = -yVel;

        } else if (getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
                + BALL_RADIUS) != null
                && getElementAt(ball.getX() + BALL_RADIUS, ball.getY()
                        + BALL_RADIUS) != paddle) {
            remove(getCollidingObject(ball.getX() + BALL_RADIUS, ball.getY()
                    + BALL_RADIUS));
            yVel = -yVel;

        } else if (getElementAt(ball.getX(), ball.getY() + BALL_RADIUS) != null
                && getElementAt(ball.getX(), ball.getY() + BALL_RADIUS) != paddle) {
            remove(getCollidingObject(ball.getX(), ball.getY() + BALL_RADIUS));
            yVel = -yVel;
        }
    }

    private void play() {
        addMouseListeners();
        ball();
        while (true) {
            checkForCollision();
            moveBall();
            pause(DELAY);
        }

    }


    private GObject getCollidingObject(double x, double y) {
        return getElementAt(x, y);

    }

    private double lastX;
    private double lastY;

    private double xVel = 5;
    private double yVel = 15;

    private GOval ball;
    private GRect paddle;
    private GObject gobj;

}

Answer 1

为什么不使用讲义 19 中建议的方法:

private GObject getCollidingObject()

也使用碰撞器:

GObject collider = getCollidingObject();

首先将墙壁碰撞和(用砖 block 划桨)游戏元素碰撞的条件分离为两个单独的方法，从而简化 else if 级联(分解我想你知道这意味着什么)。您只有两个需要担心的对象 paddle 和 bricks，因此您只需比较 (collider == paddle) 和 碰撞器!= null。此外，您仅使用半径进行比较，但应使用直径(2 * 半径)。玩得开心:)