NullReferenceException用于在单独的类中绘制精灵

问题描述

我将所有绘制方法封装到单独的类中-每种颜色一个.颜色应该在每个级别后都会改变.例如，级别1将为红色Lvl. 2橙色，Lvl. 3琥珀色(金)，依此类推.

我的Game1类或Draw_Red，Draw_Orange ...类中没有错误，但是每当我运行游戏时，都会收到NullReferenceException未处理的错误.

我没有继承所有Game1变量(这是我在旧代码中所做的工作)，而是将与绘图相关的所有变量复制并粘贴到了颜色类中.我还添加了LoadContent()方法，以便游戏在调用该类后将加载图形.我不知道缺少NullReferenceException，但是我开始怀疑我是否在所有Draw()方法的括号中都需要"SpriteBatch spriteBatch".如果可以，为什么需要在代码顶部调用SpriteBatch类?任何见解都很棒！

谢谢！

I encapsulated all of my drawing methods into separate classes - one for each color. The color is supposed to change after every level. For example, Level 1 would be red, Lvl. 2 orange, Lvl. 3 amber (gold) and so on.

I have no errors in my Game1 class or my Draw_Red, Draw_Orange... classes, but whenever I run the game, I get a NullReferenceException Unhandled error.

Rather than inheriting all Game1 variables, which is what I was doing in my old code, I copied and pasted any variables relative to drawing into the color classes. I also added a LoadContent() method so the game would load the graphics after calling on the class. I don''t know what I''m missing to get a NullReferenceException, but I''m starting to wonder if I need "SpriteBatch spriteBatch" in the parentheses of all my Draw() methods. If I do, why do I need to call the SpriteBatch class in at the top of my code? Any insight would be awesome!

Thanks!

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

namespace Isaak_FloodControl
{
	class Draw_Red:Microsoft.Xna.Framework.Game
	{
		SpriteBatch spriteBatch;

		//The size of the game window
		const int windowWidth = 800;
		const int windowHeight = 600;

		Texture2D Background;
		Texture2D Pieces;

		//Call, but do not create a new GameBoard
		GameBoard gameBoard;

		//Creates spaces where the game pieces will go
		public Rectangle EmptyPiece = new Rectangle(0, 288, 48, 48);

		//The size in pixels for the water graphic
		public const int MaxWaterHeight = 192;
		public const int WaterWidth = 192;

		//The position of the filled water image
		public Vector2 waterOverlayStart = new Vector2(112, 320);

		//The location where the water will be drawn
		public Vector2 waterPosition = new Vector2(576, 336);

		//Stores information about current flood
		float floodCount = 0.0f;

		public void LoadContent(ContentManager myContent)
		{
			spriteBatch = new SpriteBatch(GraphicsDevice);

			Background = myContent.Load<texture2d>
				(@"Textures\Backgrounds\Bkg_Red");
			Pieces = myContent.Load<texture2d>
				(@"Textures\Tile_Sheets\Ts_Red");
		}

		public void DrawBackground()
		{
			//Red
			spriteBatch.Draw(Background,
				new Rectangle(0, 0,
					windowWidth, windowHeight),
				Color.White);
		}

		public void DrawAnimatedWater()
		{
			int waterHeight = (int)(MaxWaterHeight * (floodCount / 100));

			//Animate the Red water
			spriteBatch.Draw(Background,
				new Rectangle(
					(int)waterPosition.X,
					(int)waterPosition.Y + (MaxWaterHeight - waterHeight),
					WaterWidth, waterHeight),
				new Rectangle(
					(int)waterOverlayStart.X,
					(int)waterOverlayStart.Y + (MaxWaterHeight - waterHeight),
					WaterWidth, waterHeight), Color.White);
		}

		//Draws an empty piece at a specific x and y location
		public void DrawEmptyPiece(int pixelX, int pixelY)
		{
			//Red
			spriteBatch.Draw(
				Pieces,
				new Rectangle(pixelX, pixelY,
					GamePiece.PieceWidth, GamePiece.PieceHeight),
				EmptyPiece, Color.White);
		}

		//Draws static unanimated piece at a specific x and y location
		public void DrawStandardPiece(int x, int y, int pixelX, int pixelY)
		{
			//Red
			spriteBatch.Draw(
				Pieces, new Rectangle(pixelX, pixelY,
					GamePiece.PieceWidth, GamePiece.PieceHeight),
				gameBoard.GetSourceRect(x, y),
				Color.White);
		}

		//Draws a falling piece at a specific x and y location
		public void DrawFallingPiece(int pixelX, int pixelY, string positionName)
		{
			//Red
			spriteBatch.Draw(
				Pieces,
				new Rectangle(pixelX, pixelY -
					gameBoard.fallingPieces[positionName].VerticalOffset,
					GamePiece.PieceWidth, GamePiece.PieceHeight),
					gameBoard.fallingPieces[positionName].GetSourceRect(),
					Color.White);
		}

		//Draws a fading piece at a specific x and y location
		public void DrawFadingPiece(int pixelX, int pixelY, string positionName)
		{
			//Red
			spriteBatch.Draw(
				Pieces,
				new Rectangle(pixelX, pixelY,
					GamePiece.PieceWidth, GamePiece.PieceHeight),
					gameBoard.fadingPieces[positionName].GetSourceRect(),
					Color.White *
					gameBoard.fadingPieces[positionName].alphaLevel);
		}

		//Draws a rotating piece at a specific x and y location
		public void DrawRotatingPiece(int pixelX, int pixelY, string positionName)
		{
			//Red
			spriteBatch.Draw(
				Pieces,
				new Rectangle(pixelX + (GamePiece.PieceWidth / 2),
					pixelY + (GamePiece.PieceHeight / 2),
					GamePiece.PieceWidth, GamePiece.PieceHeight),
				gameBoard.rotatingPieces[positionName].GetSourceRect(),
				Color.White,
				gameBoard.rotatingPieces[positionName].RotationAmount,
				new Vector2(GamePiece.PieceWidth / 2,
					GamePiece.PieceHeight / 2),
				SpriteEffects.None, 0.0f);
		}
	}
}

</texture2d></texture2d>

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