我试图创建一个简单的游戏来测试碰撞检测，但它不会正常运行。它构建得很好，但我得到这个错误在运行它:"NullReferenceException:对象引用不设置为对象的实例"。
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);
}
}
}
抛出异常的行是SpriteManager中的player.Update(gameTime, Game.Window.ClientBounds);。完整的异常消息是"System类型的未处理异常"。在Project 3.exe中发生了NullReferenceException。附加信息:对象引用未设置为对象的实例。"
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);
}
}
}
我不知道为什么它不工作。我已经尝试了很多不同的东西，但由于我是xna的新手，我可能错过了一些简单的东西。
任何帮助都将是非常感激的。
编辑:忘记添加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; }
}
}
您没有实例化position。您将position变量传递给UserControlledSprite的构造函数，但不将其应用于类范围内的变量。您需要声明另一个变量来保存position变量，该变量仅对构造函数方法可见。
这意味着UserControlledSprite对象第一次调用Update时，position += direction;将抛出NullReferenceException。老实说，我不知道你怎么没有得到编译时错误，因为position将不存在于Update的上下文中，除非你没有向我们展示整个代码。
对不起，我还不能发表评论。
当你创建一个玩家(UserControlledSprite)时，你似乎不需要从"UserControlledSprite(…parameters…)"中调用Sprite构造函数。
public UserControlledSprite(Texture2D textureImage, Vector2 position, int collisionOffset, Vector2 speed)
{
}
可能需要是:
public UserControlledSprite(Texture2D textureImage, Vector2 position, int collisionOffset, Vector2 speed)
: base(TextureImage, position, collisionOffset, speed)
{
}
设置要传递的数据也很有用。所以你传入textureImage, position, collisionOffset和speed。我看到您在Sprite类中拥有变量，但我没有看到您在使用构造函数创建它们时设置它们。除非，告诉我如果是这种情况，请传递与变量自动设置的名称相同的参数?如果不是这样，那么确保你在sprite类中实际设置了position, collisionOffset, speed和textureImage到它们实际传递的参数。我一直认为你不能在参数中使用与类的变量相同的名称。
所以你必须这样做(如果上面是真的):
public UserControlledSprite(Texture2D _textureImage, Vector2 _position, int _collisionOffset, Vector2 _speed)
: base(_textureImage, _position, _collisionOffset, _speed)
{
//Do this either here or in Sprite.
this.textureImage = _textureImage;
this.position = _position;
this.collisionOffset = _collisionOffset;
this.speed = _speed.
}