Question

“Object reference not set to an instance of an object.”

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);

        }    
    }
}

I am very new at this C# so any help would be great.

I have no idea what my error is.

---

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);
        }
    }
}

Thats the rest of the code

Answer 1

I’ve had a look through it and managed to get it to work using validation, if the sprite you are drawing has a null reference (No texture) it will ignore it and carry on drawing everything else.

Change your Draw() method in the Sprite.cs to this:

//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);
    }
}

The problem occurs because you never give “Sprite mSprite;” a texture, only a position.

Quick snippet:

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;

As you can see you only give mSprite a position of 125,245, simply assign it a texture like you have with the rest of the sprites and it will work fine.

You don’t need to remove the if(mSpriteTexture != null) from the Draw() method after you assign the texture though, if you don’t it simply means you won’t notice if something isn’t being assigned correctly, could be a pain if you’re debugging something else later.