java - randomWalk.java 我缺少什么(初学者)

Question

我已经编写了大部分代码，只是在完成时遇到一些困难。我应该创建一些代码，让一个正方形在绘图板上随机走动，直到它离开屏幕。我可以让它发挥一点作用，但我感觉它不正确。任何帮助将不胜感激。

这是一个它应该是什么样子的例子

这是我的代码，到目前为止我最关心的问题是 walkRandom 方法，它旁边有星星

public class RandomWalk {

// DrawingPanel will have dimensions DIM by DIM
public static final int DIM = 400;

// Start the random walk in the center of the screen
public static final int CENTER = DIM / 2;

// how big should the cursor appear?
public static final int CURSOR_DIM = 10;

// how long should the cursor saty in one place?
public static final int SLEEP_TIME = 5; // milliseconds

public static void main( String[] args ) {
    DrawingPanel panel = new DrawingPanel( DIM, DIM );
    
    Random rand = new Random();
    
    walkRandomly( panel, rand );
}

/**
 * Draw a random walk on the panel.
 * Stop as soon as you walk off the panel.
 * Each random step should go only in one
 * of these directions: left, right, up, down.
 * @param panel a DrawingPanel to draw the
 *        random walk on
 * @param rand a Java Random object to be
 *        used to generate random steps
 */
public static void walkRandomly( DrawingPanel panel, Random rand ) {
    Graphics g = panel.getGraphics();
    
    // start in center of panel
    int x = CENTER;
    int y = CENTER;
    
    // Randomly step left, right, up, or down
    // until cursor goes off screen.
    while ( onScreen( x, y ) ) {
    
        // Draw the cursor in BLACK
        g.fillRect(x, y, CURSOR_DIM, CURSOR_DIM);
        // Wait a bit.
        panel.sleep( SLEEP_TIME );
        // Show a shadow version of the cursor
        g.setColor(Color.GRAY);
        g.fillRect(x, y, CURSOR_DIM, CURSOR_DIM);
        
        
        // Choose a new location for the cursor
        //*********************************
        if (rand.nextInt() < DIM - 300){
            x--;
        } else if (rand.nextInt() < DIM / 2){
            x++;
        } else if (rand.nextInt() < DIM - 100){
            y--;
        } else if (rand.nextInt() < DIM) {
            y++;
        }
        //*********************************
         
        
        // draw the cursor at its new location
        g.setColor(Color.BLACK);
        g.fillRect(x, y, CURSOR_DIM, CURSOR_DIM);
    }
}

/**
 * determine whether (x, y) is a point on the panel.
 * @param x the x-coord of the cursor
 * @param y the y-coord of the cursor
 * @return true if (x,y) is on the screen,
 *         false if (x,y) is off the screen
 */
public static boolean onScreen( int x, int y ) {
    // x/y high = 400, x/y low = 0
    //*********************************
    return (x <= DIM && x >= 0 || y <= DIM && y >= 0);
  
}
}

Answer 1

您的代码存在一些问题。您的问题没有完全澄清，但我认为:

• 所有方向发生的概率应该相同
• 光标只能移动“完整步”，即它必须移动 CURSOR_DIM一次不少于(这就是您的示例中似乎发生的情况)

问题主要出在方法walkRandomly上，我建议你选择下一步的方向如下:

// Choose a new location for the cursor
    int direction = rand.nextInt(4);  //0=left, 1=right, 2=up, 3=down
    if (direction == 0){
        x -= CURSOR_DIM; //The step should be equal to the cursor width, not 1
    } else if (direction == 1){
        x += CURSOR_DIM;
    } else if (direction == 2){
        //you usually subtract to go up, the origin being the upper-left corner
        y -= CURSOR_DIM;
    } else if (direction == 3) {
        y += CURSOR_DIM;
    }

还有另外两个问题:

1. 您在循环的开始和结束处将光标绘制为黑色，这是多余的。您可以删除其中之一并获得相同的结果。

2. 在 onScreen方法，x和y值等于 DIM应该返回 false，因为通常图像/数组的边界是 0 到 DIM 独家。您还应该替换 ||通过 AND，因为光标应该在 x AND y 范围内，而不是 OR。
   return (x < DIM && x >= 0 && y < DIM && y >= 0);

希望对你有帮助