只有一块砖在突破游戏中消失

Question

我是Java新手，正在从斯坦福大学YouTube课程中学习。

所以我正在尝试完成他们的任务，制作breakout game，到目前为止这么好。我拥有所有的砖块，球和桨，包括游戏机制，但是当我运行游戏时，只有一块砖可以在被球击中时移除。见this。那块砖恰好是添加到画布上的最后一块砖。

球刚刚飞过所有其他砖块，没有任何效果。相关代码如下。

我在这里缺乏关于getElementAt的一些重要知识吗？我有一种感觉，getCollidingObject没有被分配给collider，这使得碰撞检测有问题。我希望有人能够就此启发我！

private void addBallMotion(){ 
// y component of starting velocity; pixels per second 
    vy = 3.0; 

/* x component of starting velocity; pixels per second 
* which ranges according to the random generator 
* can be negative or positive, ball can go left or right with equal chances 
*/ 
    vx = rgen.nextDouble(1.0, 3.0); 
    if (rgen.nextBoolean(0.5)){ 
    vx = -vx; 
    } 
    while (true){ 
    ball.move(vx, vy); 
    checkCollision(); 
    pause(FPS); 
    } 
} 

private void checkCollision(){ 
    checkWallCollision(); 
    checkBrickAndPaddleCollision(); 
} 

private void checkWallCollision(){ 
    //checks for left or right collision 
    if ((ball.getX() < leftBounds.getX()) || (ball.getX() + BALL_RADIUS * 2 > rightBounds.getX())){ 
    vx = -vx; 
    } 
    //checks for top or bottom collision 
    if ((ball.getY() < topBounds.getY()) || (ball.getY() + BALL_RADIUS * 2 > bottomBounds.getY())){ 
    vy = -vy; 
    } 
} 

private void checkBrickAndPaddleCollision(){ 
    GObject collider = getCollidingObject(); 
    if (collider == brick){ 
    remove(collider); 
    vy = -vy; 
    } 
    if (collider == paddle){ 
    vy = -vy; 
    } 
} 

//check for collision at the 4 edges of the ball 
//starting with the left and going clockwise 
private GObject getCollidingObject(){ 
    GObject ballLeft= getElementAt (ball.getX() - 1, ball.getY() + BALL_RADIUS); 
    GObject ballRight= getElementAt (ball.getX() + BALL_RADIUS * 2 + 1, ball.getY() + BALL_RADIUS); 
    GObject ballTop = getElementAt (ball.getX() + BALL_RADIUS * 2, ball.getY() - 1); 
    GObject ballBottom= getElementAt (ball.getX() + BALL_RADIUS, ball.getY() + BALL_RADIUS * 2 + 1); 

    if (ballLeft != null){ 
    return (ballLeft); 
    } 
    else if (ballTop != null){ 
    return (ballTop); 
    } 
    else if (ballRight != null){ 
    return (ballRight); 
    } 
    else if (ballBottom != null){ 
    return (ballBottom); 
    } 
    return (null); 
} 

private GRect paddle; // creates a paddle that only moves linearly according to mouses' x coordinate 
private GRect brick; 
private GOval ball; 
private double vx, vy; // x and y components of the ball's velocity 
//private GObject collider; 

这里的整个程序：

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

import java.applet.*; 
import java.awt.*; 
import java.awt.event.*; 

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; 

    /** Offset of the side bricks from the sides of game window */ 
    private static final int BRICK_X_OFFSET = ((WIDTH - NBRICKS_PER_ROW * (BRICK_WIDTH + BRICK_SEP) + BRICK_SEP)/2); 

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

    /** Number of frames per second */ 
    private static final int FPS = 1; 

    /* Method: run() */ 
    /** Runs the Breakout program. */ 
    public void run() { 
    addMouseListeners(); 
    addWorld(); 
    // runGame(); 
    } 
    private void addWorld(){ 
    setSize (APPLICATION_WIDTH, APPLICATION_HEIGHT); 
    addPlayingBox(); 
    addBricks(); 
    addPaddle(); 
    addBall(); 
    // addCounter(); 
    } 

    //adds the bound area onto screen 
    private void addPlayingBox(){ 
    topBounds = new GLine (0, 0, WIDTH, 0); 
    bottomBounds = new GLine (0, HEIGHT, WIDTH, HEIGHT); 
    leftBounds = new GLine (0, 0, 0, HEIGHT); 
    rightBounds = new GLine (WIDTH, 0, WIDTH, HEIGHT); 
    add (topBounds); 
    add (bottomBounds); 
    add (leftBounds); 
    add (rightBounds); 
    } 

    private void addBricks(){ 
    for (int i = 0; i < NBRICK_ROWS; i++){ 
     int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP)); 

     for (int j = 0; j < NBRICKS_PER_ROW; j++){ 
     int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP)); 
     brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT); 
     colorBrick(brick, i); 
     add (brick); 
     } 
    } 
    } 

    // every consecutive 2 rows are colored the same 
    private void colorBrick(GRect brick, int rowNumber){ 
    brick.setFilled (true); 
    switch (rowNumber + 1) { 
     case 1: case 2: brick.setColor(Color.red); 
     break; 
     case 3: case 4: brick.setColor(Color.orange); 
     break; 
     case 5: case 6: brick.setColor(Color.yellow); 
     break; 
     case 7: case 8: brick.setColor(Color.green); 
     break; 
     case 9: case 10:brick.setColor(Color.cyan); 
     break; 
    } 
    } 

    //adds paddle to screen 
    private void addPaddle(){ 
    paddle = new GRect (PADDLE_WIDTH, PADDLE_HEIGHT); 
    paddle.setFilled(true); 
    paddle.setColor (Color.BLACK); 
    add (paddle); 
    } 

    //creates motion for the paddle according to mouse movement 
    public void mouseMoved(MouseEvent e){ 
    paddle.setLocation ((e.getX() - PADDLE_WIDTH/2), (double) (HEIGHT - PADDLE_Y_OFFSET)); 

    /* checks if the paddle within the playing area 
    * if not the paddles will stay at the extremities*/ 
    if (paddle.getX() > (WIDTH - PADDLE_WIDTH)){ 
     paddle.setLocation((double) (WIDTH - PADDLE_WIDTH), (double) (HEIGHT - PADDLE_Y_OFFSET)); 
    } 
    if (paddle.getX() < 0){ 
     paddle.setLocation((double) 0, (double) (APPLICATION_HEIGHT - PADDLE_Y_OFFSET)); 
    } 
    } 

    private void addBall(){ 
    ball = new GOval (((WIDTH - BALL_RADIUS * 2)/2), ((HEIGHT - BALL_RADIUS * 2)/2), 
       BALL_RADIUS * 2, BALL_RADIUS * 2); 
    ball.setFilled(true); 
    ball.setColor(Color.BLACK); 
    add (ball); 
    addBallMotion(); 
    } 

    private void addBallMotion(){ 
    // y component of starting velocity; pixels per second 
    vy = 3.0; 

    /* x component of starting velocity; pixels per second 
    * which ranges according to the random generator 
    * can be negative or positive, ball can go left or right with equal chances 
    */ 
    vx = rgen.nextDouble(1.0, 3.0); 
    if (rgen.nextBoolean(0.5)){ 
     vx = -vx; 
    } 
    while (true){ 
     ball.move(vx, vy); 
     checkCollision(); 
     pause(FPS); 
    } 
    } 

    private void checkCollision(){ 
    checkWallCollision(); 
    checkBrickAndPaddleCollision(); 
    } 

    private void checkWallCollision(){ 
    //checks for left or right collision 
    if ((ball.getX() < leftBounds.getX()) || (ball.getX() + BALL_RADIUS * 2 > rightBounds.getX())){ 
     vx = -vx; 
    } 
    //checks for top or bottom collision 
    if ((ball.getY() < topBounds.getY()) || (ball.getY() + BALL_RADIUS * 2 > bottomBounds.getY())){ 
     vy = -vy; 
    } 
    } 

    private void checkBrickAndPaddleCollision(){ 
    GObject collider = getCollidingObject(); 
    if (collider == brick){ 
     remove(collider); 
     vy = -vy; 
    } 
    if (collider == paddle){ 
     vy = -vy; 
    } 
    } 

    //check for collision at the 4 edges of the ball 
    //starting with the left and going clockwise 
    private GObject getCollidingObject(){ 
    GObject ballLeft= getElementAt (ball.getX() - 1, ball.getY() + BALL_RADIUS); 
    GObject ballRight= getElementAt (ball.getX() + BALL_RADIUS * 2 + 1, ball.getY() + BALL_RADIUS); 
    GObject ballTop = getElementAt (ball.getX() + BALL_RADIUS * 2, ball.getY() - 1); 
    GObject ballBottom= getElementAt (ball.getX() + BALL_RADIUS, ball.getY() + BALL_RADIUS * 2 + 1); 

    if (ballLeft != null){ 
     return (ballLeft); 
    } 
    else if (ballTop != null){ 
     return (ballTop); 
    } 
    else if (ballRight != null){ 
     return (ballRight); 
    } 
    else if (ballBottom != null){ 
     return (ballBottom); 
    } 
    return (null); 
    } 

    private GRect paddle; // creates a paddle that only moves linearly according to mouses' x coordinate 
    private GRect brick; 
    private GOval ball; 
    private double vx, vy; // x and y components of the ball's velocity 
    private RandomGenerator rgen = RandomGenerator.getInstance(); 
    //private GObject collider; 
    private GLine topBounds; // creates a bounding box that is the playing area 
    private GLine bottomBounds; 
    private GLine leftBounds; 
    private GLine rightBounds; 
} 

Answer 1

正是我想。 Look - 你的课堂上有一个名为brick的领域。这是GRect类型。在开始时，您打电话addWorld()方法，该方法调用addBricks()。现在检查你写的是：

private void addBricks(){ 
    for (int i = 0; i < NBRICK_ROWS; i++){ 
     int y = BRICK_Y_OFFSET + (i * (BRICK_HEIGHT + BRICK_SEP)); 

     for (int j = 0; j < NBRICKS_PER_ROW; j++){ 
      int x = (BRICK_X_OFFSET) + (j * (BRICK_WIDTH + BRICK_SEP)); 
      brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT); 
      colorBrick(brick, i); 
      add (brick); 
     } 
    } 
} 

那里会发生什么？你有一个循环，其中brick被覆盖NBRICK_ROWS * NBRICKS_PER_ROW次，这会导致brick字段成为屏幕上最后创建的砖。

基本上，你在做一些与此类似：

int x; 
x = 5; 
x = 6; 
x = 8; 
// x is 8 now 

而且在checkBrickAndPaddleCollision()你只检查是否对撞机是brick。换句话说，就是说，你正在检查它是否是最后一块砖 - 如果是，那么你将它移除。

首先，您应该创建一个砖块数组，而不只是一个字段。

ArrayList<GRect> bricks; 

代替：

GRect brick; 

然后在addBricks()方法，你应该有：中

bricks.add(new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT)); 

代替：

brick = new GRect (x, y, BRICK_WIDTH, BRICK_HEIGHT); 

在此之后，在checkBrickAndPaddleCollision()，你不应该检查：

if (collider == brick) { 
    remove(collider); 
    vy = -vy; 
} 

而是所有的砖块：

for(GRect brick : bricks) { 
    if (collider.equals(brick)) { // Note that you should rather use .equals, instead of == as Aurand stated in his comment 
     remove(collider); 
     vy = -vy; 
    } 
}