Question

我有一个会射出射弹的物体，我试图使用一个列表在火箭队中产生（射弹），所以我可以在它们与物体碰撞时删除它们。所以我先创建List<Rectangle> Rockets;然后添加一个函数，让火箭产生并不断发射：

        if (Time > 0.2)
        {
            Time = 0;

            Rockets.Add(new Rectangle((int)Position.X, (int)Position.Y, rocketTexture.Width, rocketTexture.Height));
        }

然后我尝试更新它们，以便它们通过做一个foreach在屏幕上移动：

        foreach (Rectangle r in Rockets)
        {
        }

问题

这是我遇到困难的地方，我如何调用每个Rocket列表中的x和y值，以便我可以在屏幕上移动它？

我可能会想到这一点，并且有一种更简单的方法可以制造大量的射弹，并且当它们与某种方式发生碰撞或者当它们走得太远时让它们消失。

Answer 1

在游戏开发中，你宁愿使用update（）方法实现一个Rocket类，你可以通过一些speed_x和speed_y属性来移动火箭。然后，您将在主run（）方法中通过调用Rocket.getRect（）（或者只是一个.Rect属性来检查冲突，该属性可以在父类Entity中实现）。

话虽如此，我可能没有理解这个问题。

Answer 2

这是一个代码示例，希望它有所帮助

class Rocket
{
    int _life;
    public Rocket(Vector2 position, Vector2 direction)
    {
        _position = position;
        _direction = direction;
        //life of rocket. Once it reaches zero the rocket is removed.
        _life = 100;
    }

    Vector2 _position
    public Vector2 Position
    {
        get
        {
            return _position;
        }
    }

    Vector2 _velocity;
    Vector2 Velocity
    {
        get
        {
            return _velocity;
        }
    }

    public int Life
    {
        get
        {
            return _life;
        }
    }

    public void Update(World world)
    {
        _life--;
        _position += _velocity;
        //could check for collisions here, eg:
        foreach (Ship ship in world.Ships)
        {
            if (Intersects(ship))
            {
                //collision!
                //destroy this rocket
                _life = 0;
                //damage the ship the rocket hit
                ship.ApplyDamage(10);
                return;
           }
        }
    }
}

class Game
{
    List<Rocket> _rockets = new List<Rocket>();

    List<Rocket> _deadRockets = new List<Rocket>();

    void Update(GameTime gameTime)
    {
        //.ToArray() is used here because the .net list does not allow items to be removed while iterating over it in a loop. 
        //But we want to remove rockets when they are dead. So .ToArray() means we are looping over the array not the 
        //list, so that means we are free to remove items from the list. basically it's a hack to make things simpler...
        foreach (Rocket rocket in _rockets.ToArray())
        {
            //world is an object that contains references to everything on the map
            //so that the rocket has access to that stuff as part of it's update
            rocket.Update( world );


            //if the rocket has run out of life then remove it from the list
            if (rocket.Life <= 0)
                _rockets.Remove(rocket);
        }
    }

    void FireRocket(Vector2 from, Vector2 direction)
    {
        Rocket newRocket = new Rocket(from, direction);
        _rockets.Add(newRocket);
    }
}

Answer 3

执行for循环而不是foreach循环。我还建议使用数组（并创建一个Rocket类而不仅仅是Vector2s。）

for (int i = 0; i < Rockets.Count; i++)
{
   Rockets[i] = new Rectangle(Rockets[i].X + 20, Rockets[i].Y + 20);
}

将弹丸移动到列表中

3 个答案: