Question

我想创建一个类，在我触摸[手机屏幕上的XY点]的点上拍摄。我搜索了很多，但我找不到任何好的资源来阅读。我创建了一个只能在X方向拍摄的类。我还上传了图片。任何帮助将不胜感激。

提前致谢。

public class Gun {

    private float x, y;
    private int speedX;
    private boolean Visible;
    private Rect rect;

    public Gun (int startX, int startY)
    {
        x = startX;
        y = startY;
        speedX = 220;
        Visible = true;
        rect = new Rect();  
    }

    public void update(float delta)
    {
        x += speedX*delta;
        if (x > 800)
        {
            Visible = false;
        }
        updateRect();
    }

    private void updateRect()
    {
        rect.set((int) x, (int) y, (int) x + 20, (int) y + 10);
    }

    public void onCollideWith(Enemy e)
    {
        Visible = false;
    }

这是我更新的最新代码但是有一点问题。

    public class Gum {
    private float x,y; // x & y position of the gun
    private float bulletSpeed,speedX,speedY;     
    //speedX and speedY are define to update x & y position of bullets
    private boolean Visible;
    private Rect rect;
    private float handlerX, handlerY; //to get the X and Y value of the touch
    public Gum(int startX, int startY)
        {
          x = startX;
          y = startY;
          bulletSpeed = 220; //
          Visible = true;
          rect = new Rect();
        }
     public void update(float delta)
        {
          x+= speedX*delta;
          y += speedY*delta;
          if(x>800 || y >450)
                {
                    Visible = false;
                 }
         updateBullets();
         updateRect();
        }
     private void updateBullets()
        {   
            handlerX =  InputHandler.scaledX ;
            handlerY = InputHandler.scaledY ;
            //location of the touch - location of the gun
            float deltaX = handlerX - x; 
          /*   THIS DEFINE IN ANOTHER CLASS (InputHandler)
             * scaledX = (int) ((event.getX() / v.getWidth())* *GameMainActivity.GAME_WIDTH);      
             scaledY = (int) ((event.getY() / v.getHeight()) * GameMainActivity.GAME_HEIGHT);

          */

              float deltaY = handlerY - y;
              float length =(float) ( Math.sqrt(Math.pow(deltaX, 2)) + Math.pow(deltaY, 2));

              float normalDeltaX = deltaX/ length;
              float normalDeltaY = deltaY/length;

              speedX =  (bulletSpeed * normalDeltaX);
              speedY = bulletSpeed * normalDeltaY;

}

**这是问题的YOUTUBE视频** https://youtu.be/C6AdnU_2Qz4

Answer 1

在开始之前，除了speedY变量之外，还需要声明speedX变量。在update（）方法中使用它来更新y位置，就像使用speedX和x位置一样。此外，您应该使用speedX和speedY变量float而不是int。

这是你为了让子弹进入玩家所做的工作（在你班级的构造函数中这样做）：

//First you need to find the tap position.
//In libgdx you can do this using Gdx.input.getX() and Gdx.input.getY()
float tapX = Gdx.input.getX();
float tapY = Gdx.input.getY();

//Calculate the x and y distance from the gun to the tap.
//This gives us a vector between the player and the tap position.
float dx = tapX - x;
float dy = tapY - y;

//Now we need to normalize the vector so that it is of length 1.
//This is so that we can control the speed of the bullet.
//First use the pythagorean theorem to calculate the length of the vector
//(this is the same as the distance between the player and the tap position).
float length = (float)Math.sqrt(dx*dx + dy*dy);

//failsafe to avoid division by zero
if (length == 0)
{
    length = 1;
    dx = 1;
    dy = 0;
}

//Divide the vector components by the length to make it length one.
dx /= length;
dy /= length;

//Now we can calculate the x and y speed of the bullet!
final float bulletSpeed = 220; //change this number to speed up or slow down the bullet
speedX = bulletSpeed * dx;
speedY = bulletSpeed * dy;

如果您对此有任何疑问，请随时提出。

在XY方向拍摄

1 个答案: