java - Android Math不起作用

private void gotoPos()
{
    spaceX = x2 - x;
    spaceY = y2 - y;
    if (Math.abs(spaceX) >= Math.abs(spaceY)) {
        xSpeed = Math.round(spaceX * (3/Math.abs(spaceX)));
        ySpeed = Math.round(spaceY * (3/Math.abs(spaceX)));
    }

使用此代码，我想将对象移动到位置x2和y2。 x和y是对象的当前位置。 spaceX是对象与应该到达的x位置之间的空间。对于spaceY也是一样。

但是我不希望对象每次平移超过3个像素。

示例：对象位置：x = 35，y = 22

将其指向：x2 = 79，y2 = 46

它们之间的空间：spaceX = 79-35 = 44，spaceY = 46-22 = 24

spaceX大于spaceY，因此：

xSpeed = 44 *（3/44）= 3，ySpeed = 24 *（3/44）= 1.63 = 2

但这不是这样的。当我启动应用程序时，对象不会转到x2和y2。
如果我改变
xSpeed = spaceX;
ySpeed = spaceY;

物体移动到该位置，但我不希望它立即移动到该位置

完整代码：

public class Sprite
{
private boolean walking = true;
private int actionWalk = 0;
private Random rnd;
private int checkIfAction;
private int nextAction = 0;
static final private int BMP_COLUMNS = 4;
static final private int BMP_ROWS = 4;
private int[] DIRECTION_TO_SPRITE_SHEET = { 1, 0, 3, 2 };
public int x=-1;
private int y=-1;
public int xSpeed;
private int ySpeed;
private int width;
private int height;
private int bottomSpace;
private Bitmap bmp;
private GameView theGameView;
private int currentFrame=0;
private int x2, y2;
private boolean isTouched;
private int spaceX, spaceY;

d

public Sprite(GameView theGameView, Bitmap bmp)
{
    this.theGameView = theGameView;
    this.bmp = bmp;
    this.width = bmp.getWidth() / BMP_COLUMNS;
    this.height = bmp.getHeight() / BMP_ROWS;
    rnd = new Random();
    xSpeed = 0;
    ySpeed = 0;
}

public void shareTouch(float xTouch, float yTouch)
{
    x2 = (int) xTouch;
    y2 = (int) yTouch;
    isTouched = true;
}
    private void gotoPos()
{
    spaceX = x2 - x;
    spaceY = y2 - y;
    if (Math.abs(spaceX) >= Math.abs(spaceY)) {
        xSpeed = Math.round(spaceX * (3/Math.abs(spaceX)));
        ySpeed = Math.round(spaceY * (3/Math.abs(spaceX)));
    }
    else {
        xSpeed = spaceX;
        ySpeed = spaceY;
    }
}

d

private void bounceOff()
{
    bottomSpace = theGameView.getHeight() - y;
    if (x > theGameView.getWidth() - (width * theGameView.getDensity()) - xSpeed - bottomSpace / 2 || x + xSpeed < bottomSpace / 2)
    {
        xSpeed = -xSpeed;
    }
    x = x + xSpeed;
    if (y > theGameView.getHeight() - (height * theGameView.getDensity()) - ySpeed || y + ySpeed < theGameView.getHeight() / 2)
    {
        ySpeed = -ySpeed;
    }
    y = y + ySpeed;
    currentFrame = ++currentFrame % BMP_COLUMNS;
}

d

public void onDraw(Canvas canvas)
{
    if (x == -1)
    {
        x = (theGameView.getWidth() / 2);
        y = (theGameView.getHeight() / 2 + theGameView.getHeight() / 4);
    }
    if (isTouched == true)
    {
        gotoPos();
    }
    /*      if (nextAction == 100)
     {
     action();
     nextAction = 0;
     }
     nextAction += 1;*/
    bounceOff();
    int sourceX, sourceY;
    if (walking == true)
    {
        sourceX = currentFrame * width;
    }
    else
    {
        sourceX = 0;
    }
    sourceY = getAnimationRow() * height;
    Rect source = new Rect(sourceX, sourceY, sourceX + width, sourceY + height);
    Rect destine = new Rect(x, y, (int) (x + (width * theGameView.getDensity())), (int) (y + (height * theGameView.getDensity())));
    canvas.drawBitmap(bmp, source, destine, null);
}

d

private int getAnimationRow()
{
    double directionDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2);
    int spriteDir = (int) Math.round(directionDouble) % BMP_ROWS;
    return DIRECTION_TO_SPRITE_SHEET[spriteDir];
}

}

最佳答案

一个简单的问题：您使用整数算术，但对此不理解：

spaceX * (3/Math.abs(spaceX))

几乎在所有情况下结果都是0，因为3/x始终x > 3始终是0。

要使程序正常运行，请使用浮点算术或重写公式以使其按预期工作。

要使用浮点运算，您必须更改为

spaceX * (3.0/Math.abs(spaceX))

假设变量spaceX也是浮点数。

你也可以用

(spaceX * 3) / Math.abs(spaceX)

如果您想保留整数（我想）。