NullReferenceException in ContentManager, XNA

Question

我在XNA中遇到了NullReferenceException问题。我有4个职业:英雄，精灵，火球，Game1。通过调试，我发现问题发生在我的Fireball通过管道

加载内容之后。

    class Fireball: Sprite
    {
        const int MAX_DISTANCE = 500;
        public bool Visible = false;
        Vector2 mStartPosition;
        Vector2 mSpeed;
        Vector2 mDirection;
        public void LoadContent(ContentManager theContentManager)
        {
            base.LoadContent(theContentManager, "Fireball");
            Scale = 0.3f;
        }

然后在我的Sprite类中我尝试通过ContentManager加载我的纹理

class Sprite
    {
        //The asset name for the Sprite's Texture
        public string AssetName;
        //The Size of the Sprite (with scale applied)
        public Rectangle Size;
        //The amount to increase/decrease the size of the original sprite. 
        private float mScale = 1.0f;
        //The current position of the Sprite
        public Vector2 Position = new Vector2(0, 0);
        //The texture object used when drawing the sprite
        private Texture2D myTexture;
        //Load the texture for the sprite using the Content Pipeline
        public void LoadContent(ContentManager theContentManager, string theAssetName)
        {
            myTexture = theContentManager.Load<Texture2D>(theAssetName);
            AssetName = theAssetName;
            Source = new Rectangle(0, 0, myTexture.Width, myTexture.Height);
            Size = new Rectangle(0, 0, (int)(myTexture.Width * Scale), (int)(myTexture.Height * Scale)); ;
        }

它给了我一个NullReferenceException在myTexture = theContentManager.Load(theAssetName);线。通过调试报告，我看到资产名称中有"火球"，但ContentManager本身为空。我做错了什么?因为我是c#的新手，如果有人能告诉我应该添加哪些行和在哪里，我会很感激。如果有人需要一个完整的项目，它在这里https://www.dropbox.com/s/1e353e834rggj40/test.rar因为它有点大。

Answer 1

你没有调用LoadContent为火球从Game1这意味着你没有ContentManager。将此添加到Sprite类中:

public static ContentManager Cm;

然后在Game1

的LoadContent顶部

Sprite.Cm = this.Content;

那么它应该工作得很好，因为你保存了ContentManager在Sprite类中供以后使用。