Question

所以我有一个我无法弄清楚的问题，那就是从一个drawablegamecomponent类中将对象绘制到我的主Game1类中。

我一直在玩它并查看其他示例，但无法弄清楚问题。代码不多，所以我只发布我拥有的两个类，主类Game1和我要绘制的类，Balloon。

错误在绘制方法中我得到了这个......

An unhandled exception of type 'System.NullReferenceException' occurred in Burst.exe

Additional information: Object reference not set to an instance of an object.

主类。

   using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace Burst
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        Rectangle bounds;
        Balloon ball;
        Diamond dia;




        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            graphics.PreferredBackBufferWidth = 1152;
            graphics.PreferredBackBufferHeight = 648;
            Content.RootDirectory = "Content";


            bounds = new Rectangle(0, 0, graphics.PreferredBackBufferWidth, graphics.PreferredBackBufferHeight);

            ball = new Balloon(bounds, 1, this, spriteBatch);
            dia = new Diamond(bounds, new Vector2(200, 200), this, spriteBatch);

        }




        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here


            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);



            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            // TODO: Add your update logic here

            ball.Update();
            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            spriteBatch.Begin();
            // TODO: Add your drawing code here
            ball.Draw(gameTime);
            dia.Draw(gameTime);
            spriteBatch.End();
            base.Draw(gameTime);
        }
    }
}

气球课程：

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

namespace Burst
{

    public class Balloon : Microsoft.Xna.Framework.DrawableGameComponent
    {

        Vector2 position;
        Vector2 motion;
        Texture2D texture;
        Rectangle bounds;
        Rectangle screenBounds;
        Game game;
        SpriteBatch spriteBatch;


        float balloonSpeed = 4;

        int colour = 0;




        public Balloon(Rectangle screenBounds, int colour, Game game, SpriteBatch spriteBatch) : base (game)
        {
            this.colour = colour;
            this.game = game;
            this.spriteBatch = spriteBatch;
            this.screenBounds = screenBounds;
            this.position = new Vector2(200,200);

        }

       protected override void LoadContent()
        {

            switch (colour)
            {
                case 1: texture = Game.Content.Load<Texture2D>("Images/BlueBalloon");
                    break;
                case 2: texture = Game.Content.Load<Texture2D>("Images/GreenBalloon");
                    break;
                case 3: texture = Game.Content.Load<Texture2D>("Images/RedBalloon");
                    break;
                case 4: texture = Game.Content.Load<Texture2D>("Images/YellowBalloon");
                    break;
                case 5: texture = Game.Content.Load<Texture2D>("Images/PurpleBalloon");
                    break;
            }
        }


        public Rectangle Bounds
        {
            get
            {
                bounds.X = (int)position.X;
                bounds.Y = (int)position.Y;
                return bounds;
            }
        }


        public void Update()
        {
            position += motion * balloonSpeed;

        }

        private void CheckWallColision()
        {
            if (position.X < 0)
            {
                position.X = 0;
                motion.X *= -1;
            }

            if (position.X + texture.Width > screenBounds.Width)
            {
                position.X = screenBounds.Width - texture.Width;
                motion.X *= -1;
            }

            if (position.Y < 0)
            {
                position.Y = 0;
                motion.Y *= -1;
            }

            if (position.Y + texture.Height > screenBounds.Height)
            {

                position.Y = screenBounds.Height - texture.Height;
                motion.Y *= -1;
            }
        }

        public void SetStartPosition()
        {
            Random rand = new Random();

            motion = new Vector2(rand.Next(2, 6), -rand.Next(2, 6));
            motion.Normalize();

            position = new Vector2(200, 300);

        }


        public void Draw()
        {
            spriteBatch.Draw(texture, position, Color.White); 

        }
    }
}

Answer 1

当您创建对象“ball”和“dia”时，

“spriteBatch”== null。您需要移动此代码：

        bounds = new Rectangle(0, 0, graphics.PreferredBackBufferWidth, graphics.PreferredBackBufferHeight);

        ball = new Balloon(bounds, 1, this, spriteBatch);
        dia = new Diamond(bounds, new Vector2(200, 200), this, spriteBatch);

方法“LoadContent”。创建“spriteBatch”后。

XNA对象没有绘制

1 个答案: