Question

我有一个随机移动的图像。我的问题是每次我开始运行程序时，图像总是出现在左上角并移动一个对角线方向，在撞到墙壁后，它开始随机移动方向。每次执行或运行程序时，如何使图像显示在随机位置？任何帮助将不胜感激......

以下是代码：

public class Ball extends JPanel implements Runnable
{

private Image ball;
private Thread animator;
private int x;
private int y;
private final int DELAY = 50;
private int xVelocity = 1;
private int yVelocity = 1;
private static final int RIGHT_WALL = 400;
private static final int LEFT_WALL = 1;
private static final int DOWN_WALL = 400;
private static final int UP_WALL = 1;
private boolean showImage;

public Ball()
{
    randomPosition();
    setRandomDirection();
    setBackground(Color.BLACK);
    setDoubleBuffered(true);

    ImageIcon ii = new ImageIcon(this.getClass().getResource("ball.gif"));
    ball = ii.getImage();
    x = y = 10;

}

public void addNotify()
{
    super.addNotify();
    animator = new Thread(this);
    animator.start();
}

public void paint(Graphics g)
{
    super.paint(g);

    Graphics2D g2d = (Graphics2D) g;
    g2d.drawImage(ball, x, y, this);
    Toolkit.getDefaultToolkit().sync();
    g.dispose();
}

public void move()
{

    x += xVelocity;
    y += yVelocity;

    if (x >= RIGHT_WALL)
    {
        x = RIGHT_WALL;

        randomDirection();
    }

    if (y <= UP_WALL)
    {
        y = UP_WALL;

        randomDirection();
    }

    if (x <= LEFT_WALL)
    {
        x = LEFT_WALL;

        randomDirection();
    }
    if (y >= DOWN_WALL)
    {
        y = DOWN_WALL;

        randomDirection();
    }

}

private void randomDirection()
{
    double speed = 2.0;
    double direction = Math.random() * 2 * Math.PI;
    xVelocity = (int) (speed * Math.cos(direction));
    yVelocity = (int) (speed * Math.sin(direction));

}


private void randomPosition()
{
    x = LEFT_WALL + (int) (Math.random() * (RIGHT_WALL - LEFT_WALL));
    y = UP_WALL + (int) (Math.random() * (DOWN_WALL - UP_WALL));
}


public void run()
{
    long beforeTime, timeDiff, sleep;
    beforeTime = System.currentTimeMillis();
    while (true)
    {

        cycle();
        repaint();

        timeDiff = System.currentTimeMillis() - beforeTime;
        sleep = DELAY - timeDiff;

        if (sleep > 2)
        {
            sleep = 1;
        }
        try
        {
            Thread.sleep(sleep);
        }
        catch (InterruptedException e)
        {
            System.out.println("interrupted");
        }

        beforeTime = System.currentTimeMillis();
    }
}
}

Answer 1

您需要的只是移动物体中x和y的设定器：

public void randomStart(){
    this.x = Math.random() * this.RIGHT_WALL;
    this.y = Math.random() * this.DOWN_WALL;
}

然后你从main（）调用它。

Answer 2

与您的randomDirection()方法一样，您应该随机初始化图像的x和y位置：

private void randomPosition() {
    x = LEFT_WALL + (int) (Math.random() * (RIGHT_WALL - LEFT_WALL));
    y = UP_WALL + (int) (Math.random() * (DOWN_WALL - UP_WALL));
}

您还应该在构造函数中调用randomDirection()方法一次，这样每次启动程序时图像都会向另一个方向移动。

所以构造函数应该如下所示：

public YourClassName() {
    randomPosition();
    randomDirection();
}

Answer 3

您还必须随机生成初始值。

其实你总是采取：

private int x, y;
private int xVelocity = 1;
private int yVelocity = 1;

所以x == 0，y == 0，xVelocity == 1和yVelocity == 1作为变量的静态初始值。

Answer 4

Random r = new Random()  
public Ball()
{
    randomPosition();
    setRandomDirection();
    setBackground(Color.BLACK);
    setDoubleBuffered(true);

    ImageIcon ii = new ImageIcon(this.getClass().getResource("chicken.gif"));
    ball = ii.getImage();
    this.x = r.nextInt();
    this.y = r.nextInt();

}

每当我开始运行程序时如何制作随机位置？

4 个答案: