c# - 空引用异常

Question

“你调用的对象是空的。”

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.Graphics;

namespace XNAdev
{
    class Sprite
    {
        //The size of the Sprite
        public Rectangle Size;

        //Used to size the Sprite up or down from the original image
        public float Scale = 1.0f;

        //The current position of the Sprite
        public Vector2 Position = new Vector2(115, 0);
        //The texture object used when drawing the sprite
        private Texture2D mSpriteTexture;

        //Load the texture for the sprite using the Content Pipeline
        public void LoadContent(ContentManager theContentManager, string theAssetName)
        {
            mSpriteTexture = theContentManager.Load<Texture2D>(theAssetName);
            Size = new Rectangle(0, 0, (int)(mSpriteTexture.Width * Scale), (int)(mSpriteTexture.Height * Scale));
        }

        //Draw the sprite to the screen
        public void Draw(SpriteBatch theSpriteBatch)
        {
            theSpriteBatch.Draw(mSpriteTexture, Position,
                new Rectangle(0, 0, mSpriteTexture.Width, mSpriteTexture.Height), Color.White,
                0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0);

        }    
    }
}

我对这个 C# 很陌生，所以任何帮助都会很棒。

我不知道我的错误是什么。

namespace XNAdev
{

    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        Sprite mSprite;
        Sprite mSpriteTwo;
        Sprite mBackgroundOne;
        Sprite mBackgroundTwo;
        Sprite mBackgroundThree;
        Sprite mBackgroundFour;
        Sprite mBackgroundFive;





        public Game1()
        {           

            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        protected override void Initialize()
        {
            mSprite = new Sprite();
            mSpriteTwo = new Sprite();

            mBackgroundOne = new Sprite();
            mBackgroundOne.Scale = 2.0f;

            mBackgroundTwo = new Sprite();
            mBackgroundTwo.Scale = 2.0f;

            mBackgroundThree = new Sprite();
            mBackgroundThree.Scale = 2.0f;

            mBackgroundFour = new Sprite();
            mBackgroundFour.Scale = 2.0f;

            mBackgroundFive = new Sprite();
            mBackgroundFive.Scale = 2.0f;

            base.Initialize();
        }

        protected override void LoadContent()
        { 
            spriteBatch = new SpriteBatch(GraphicsDevice);

            mSprite.Position = new Vector2(125, 245);

            mSpriteTwo.LoadContent(this.Content, "SquareGuy");
            mSpriteTwo.Position.X = 300;
            mSpriteTwo.Position.Y = 300;

            mBackgroundOne.LoadContent(this.Content, "Background01");
            mBackgroundOne.Position = new Vector2(0, 0);            

            mBackgroundTwo.LoadContent(this.Content, "Background02");
            mBackgroundTwo.Position = new Vector2(mBackgroundOne.Position.X + mBackgroundOne.Size.Width, 0);

            mBackgroundThree.LoadContent(this.Content, "Background03");
            mBackgroundThree.Position = new Vector2(mBackgroundTwo.Position.X + mBackgroundTwo.Size.Width, 0);

            mBackgroundFour.LoadContent(this.Content, "Background04");
            mBackgroundFour.Position = new Vector2(mBackgroundThree.Position.X + mBackgroundThree.Size.Width, 0);

            mBackgroundFive.LoadContent(this.Content, "Background05");
            mBackgroundFive.Position = new Vector2(mBackgroundFour.Position.X + mBackgroundFour.Size.Width, 0);            
        }

        protected override void UnloadContent()
        {

        }


        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            if (mBackgroundOne.Position.X < -mBackgroundOne.Size.Width)
            {
                mBackgroundOne.Position.X = mBackgroundFive.Position.X + mBackgroundFive.Size.Width;
            }

            if (mBackgroundTwo.Position.X < -mBackgroundTwo.Size.Width)
            {
                mBackgroundTwo.Position.X = mBackgroundOne.Position.X + mBackgroundOne.Size.Width;
            }

            if (mBackgroundThree.Position.X < -mBackgroundThree.Size.Width)
            {
                mBackgroundThree.Position.X = mBackgroundTwo.Position.X + mBackgroundTwo.Size.Width;
            }

            if (mBackgroundFour.Position.X < -mBackgroundFour.Size.Width)
            {
                mBackgroundFour.Position.X = mBackgroundThree.Position.X + mBackgroundThree.Size.Width;
            }

            if (mBackgroundFive.Position.X < -mBackgroundFive.Size.Width)
            {
                mBackgroundFive.Position.X = mBackgroundFour.Position.X + mBackgroundFour.Size.Width;
            }

            Vector2 aDirection = new Vector2(-1, 0);
            Vector2 aSpeed = new Vector2(160, 0);

            mBackgroundOne.Position += aDirection * aSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;
            mBackgroundTwo.Position += aDirection * aSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;
            mBackgroundThree.Position += aDirection * aSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;
            mBackgroundFour.Position += aDirection * aSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;            
            mBackgroundFive.Position += aDirection * aSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds;            
        }

        protected override void Draw(GameTime gameTime)
        {
            graphics.GraphicsDevice.Clear(Color.CornflowerBlue);          

            spriteBatch.Begin();

            mBackgroundOne.Draw(this.spriteBatch);
            mBackgroundTwo.Draw(this.spriteBatch);
            mBackgroundThree.Draw(this.spriteBatch);
            mBackgroundFour.Draw(this.spriteBatch);
            mBackgroundFive.Draw(this.spriteBatch);

            mSprite.Draw(this.spriteBatch);
            mSpriteTwo.Draw(this.spriteBatch);
            spriteBatch.End();

            base.Draw(gameTime);
        }
    }
}

这就是剩下的代码

score 7 · Accepted Answer

查找如何设置 Visual Studio 以中断异常。
了解如何使用调试器，以便您可以单步执行代码以查看错误发生的位置。

score 1 · Accepted Answer

我已经查看了它并设法使用验证使其工作，如果您正在绘制的精灵具有空引用（无纹理），它将忽略它并继续绘制其他所有内容。

将 Sprite.cs 中的 Draw() 方法更改为：

//Draw the sprite to the screen
public void Draw(SpriteBatch theSpriteBatch)
{
    if (mSpriteTexture != null)
    {
        theSpriteBatch.Draw(mSpriteTexture, Position,
            new Rectangle(0, 0, mSpriteTexture.Width, mSpriteTexture.Height), Color.White,
            0.0f, Vector2.Zero, Scale, SpriteEffects.None, 0);
    }
}

出现问题是因为您从不给“ Sprite mSprite; ”一个纹理，只给一个位置。

快速片段：

protected override void LoadContent()
{
    spriteBatch = new SpriteBatch(GraphicsDevice);

    mSprite.Position = new Vector2(125, 245);

    mSpriteTwo.LoadContent(this.Content, "SquareGuy");
    mSpriteTwo.Position.X = 300;
    mSpriteTwo.Position.Y = 300;

如您所见，您只为 mSprite 提供了 125,245 的位置，只需像其他精灵一样为其分配一个纹理，它就可以正常工作。

分配纹理后，您无需if(mSpriteTexture != null)从 Draw() 方法中删除稍后重新调试其他东西。

score 0 · Accepted Answer

可能你应该检查

 mSpriteTexture = theContentManager.Load<Texture2D>(theAssetName);
 if (mSpriteTexture != null)
     Size = new Rectangle(0, 0, (int)(mSpriteTexture.Width * Scale), (int)(mSpriteTexture.Height * Scale));

在 Draw 函数中也是如此。

score 0 · Accepted Answer

此错误表示已尝试在未实例化对象的情况下访问对象的字段或方法之一。

对于您的代码，这似乎是在对象 mSpriteTexture 上发生的。

你应该添加

mSpriteTexture = new Texture2D();

某处，但我不能只用这段代码告诉哪里。

c# - 空引用异常

4 回答 4

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