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我試圖創建一個簡單的遊戲來測試碰撞檢測，但它不會正常運行。它構建得很好，但運行時出現此錯誤：「NullReferenceException：對象引用未設置爲對象的實例」。xna中的NullReferenceException
SpriteManager.cs：
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 Project_3
{
public class SpriteManager : Microsoft.Xna.Framework.DrawableGameComponent
{
private Game1 _Game1;
//SpriteBatch for drawing
SpriteBatch spriteBatch;
//A sprite for the player and a list of automated sprites
UserControlledSprite player;
List<Sprite> spriteList = new List<Sprite>();
public SpriteManager(Game1 game)
: base(game)
{
// TODO: Construct any child components here
_Game1 = game;
}
public override void Initialize()
{
// TODO: Add your initialization code here
base.Initialize();
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(Game.GraphicsDevice);
//Load the player sprite
player = new UserControlledSprite(
Game.Content.Load<Texture2D>("Images/bill"),
Vector2.Zero, 10, new Vector2(6, 6));
//Load several different automated sprites into the list
spriteList.Add(new AutomatedSprite(
Game.Content.Load<Texture2D>("Images/kit"),
new Vector2(150, 150), 10, Vector2.Zero));
spriteList.Add(new AutomatedSprite(
Game.Content.Load<Texture2D>("Images/kit"),
new Vector2(300, 150), 10, Vector2.Zero));
spriteList.Add(new AutomatedSprite(
Game.Content.Load<Texture2D>("Images/beast"),
new Vector2(150, 300), 10, Vector2.Zero));
spriteList.Add(new AutomatedSprite(
Game.Content.Load<Texture2D>("Images/beast"),
new Vector2(600, 400), 10, Vector2.Zero));
base.LoadContent();
}
public override void Update(GameTime gameTime)
{
// Update player
player.Update(gameTime, Game.Window.ClientBounds);
// Update all sprites
foreach (Sprite s in spriteList)
{
s.Update(gameTime, Game.Window.ClientBounds);
}
base.Update(gameTime);
}
public override void Draw(GameTime gameTime)
{
spriteBatch.Begin(SpriteSortMode.FrontToBack, BlendState.AlphaBlend);
// Draw the player
player.Draw(gameTime, spriteBatch);
// Draw all sprites
foreach (Sprite s in spriteList)
s.Draw(gameTime, spriteBatch);
spriteBatch.End();
base.Draw(gameTime);
}
}
}
拋出異常是從SpriteManagerplayer.Update(gameTime, Game.Window.ClientBounds);線。完整的異常消息是「在Project 3.exe中發生了類型爲」System.NullReferenceException「的未處理異常。附加信息：未將對象引用設置爲對象實例。」
UserControlledSprite.cs：
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.Input;
namespace Project_3
{
class UserControlledSprite : Sprite
{
// Movement stuff
MouseState prevMouseState;
// Get direction of sprite based on player input and speed
public override Vector2 direction
{
get
{
Vector2 inputDirection = Vector2.Zero;
// If player pressed arrow keys, move the sprite
if (Keyboard.GetState().IsKeyDown(Keys.Left))
inputDirection.X -= 1;
if (Keyboard.GetState().IsKeyDown(Keys.Right))
inputDirection.X += 1;
if (Keyboard.GetState().IsKeyDown(Keys.Up))
inputDirection.Y -= 1;
if (Keyboard.GetState().IsKeyDown(Keys.Down))
inputDirection.Y += 1;
// If player pressed the gamepad thumbstick, move the sprite
GamePadState gamepadState = GamePad.GetState(PlayerIndex.One);
if (gamepadState.ThumbSticks.Left.X != 0)
inputDirection.X += gamepadState.ThumbSticks.Left.X;
if (gamepadState.ThumbSticks.Left.Y != 0)
inputDirection.Y -= gamepadState.ThumbSticks.Left.Y;
return inputDirection * speed;
}
}
public UserControlledSprite(Texture2D textureImage, Vector2 position, int collisionOffset, Vector2 speed)
{
}
public override void Update(GameTime gameTime, Rectangle clientBounds)
{
// Move the sprite based on direction
position += direction;
// If player moved the mouse, move the sprite
MouseState currMouseState = Mouse.GetState();
if (currMouseState.X != prevMouseState.X ||
currMouseState.Y != prevMouseState.Y)
{
position = new Vector2(currMouseState.X, currMouseState.Y);
}
prevMouseState = currMouseState;
// If sprite is off the screen, move it back within the game window
if (position.X < 0)
position.X = 0;
if (position.Y < 0)
position.Y = 0;
if (position.X > clientBounds.Width - 150)
position.X = clientBounds.Width - 150;
if (position.Y > clientBounds.Height - 150)
position.Y = clientBounds.Height - 150;
base.Update(gameTime, clientBounds);
}
}
}
我不知道爲什麼它不工作。我嘗試了一堆不同的東西，但由於我對xna很陌生，因此我可能錯過了一些簡單的東西。
任何幫助將不勝感激。
編輯：忘了補充Sprite.cs：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
namespace Project_3
{
abstract class Sprite
{
// Stuff needed to draw the sprite
Texture2D textureImage;
// Collision data
int collisionOffset;
// Movement data
protected Vector2 speed;
protected Vector2 position;
// Abstract definition of direction property
public abstract Vector2 direction
{
get;
}
public Sprite()
{
}
public Sprite(Texture2D textureImage, Vector2 position, int collisionOffset, Vector2 speed)
//: this(textureImage, position, collisionOffset, speed)
{
}
public virtual void Update(GameTime gameTime, Rectangle clientBounds)
{
}
public virtual void Draw(GameTime gameTime, SpriteBatch spriteBatch)
{
// Draw the sprite
if (textureImage != null)
{
spriteBatch.Draw(textureImage, position, Color.White);
}
}
// Gets the collision rect based on position, framesize and collision offset
public Rectangle collisionRect
{
get
{
return new Rectangle(
(int)position.X + collisionOffset,
(int)position.Y + collisionOffset,
150 - (collisionOffset * 2),
150 - (collisionOffset * 2));
}
}
public Game1 _Game1 { get; set; }
}
}
嘗試Game.Content.Load（「/ Images/bill」）注意/之前圖像 –
Alekstim
2013-03-22 20:06:49
Visual Studio調試器允許您將鼠標懸停在變量上以查看其值。做到這一點，並找出哪個變量是null，這是取消引用。 – 2013-03-22 20:07:54
'player'爲null。我嘗試了一些不同的東西，但我不確定如何調試這樣的東西。 – 2013-03-22 20:13:13