此方法不接受此参数的空值。

Question

我想为windows phone 7制作一个宠物护理游戏，但我有问题，它告诉我我有一个空方法，但我不知道为什么我在游戏中每个州都有一个枚举。

下面是消息的图片：new=10%253A1377747418

这是主文件。

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.Input.Touch;
using Microsoft.Xna.Framework.Media;
using Mochi_Mochi_Pets_Life.Script.Screen;

namespace Mochi_Mochi_Pets_Life
{

public class MainFile : Microsoft.Xna.Framework.Game
{
    GraphicsDeviceManager graphics;
    SpriteBatch spriteBatch;
    ScreenStates screentState;

    Rectangle TouchS_Y_X;

    Logo logo;
    Menu0 menu;
    Choose_Pets choose_pets;
    ScreenStates.CurrentGameState GameState;

    public MainFile()
    {
        graphics = new GraphicsDeviceManager(this);
        Content.RootDirectory = "Content";
        Content.RootDirectory = "Script\\Screen";

        choose_pets = new Choose_Pets();

        this.screentState = new ScreenStates();
        this.logo = new Logo(GraphicsDevice);
        this.menu = new Menu0();
        // Frame rate is 30 fps by default for Windows Phone.
        TargetElapsedTime = TimeSpan.FromTicks(333333);

        // Extend battery life under lock.
        InactiveSleepTime = TimeSpan.FromSeconds(1);

        GameState = ScreenStates.CurrentGameState.Logo;


    }


    protected override void Initialize()
    {
        choose_pets.Initialize_choosepets();
        // TODO: Add your initialization logic here
        base.Initialize();
    }


    protected override void LoadContent()
    {
        TouchS_Y_X = new Rectangle(0, 0, 1, 1);
        // Create a new SpriteBatch, which can be used to draw textures.
        spriteBatch = new SpriteBatch(GraphicsDevice);

        if (GameState == ScreenStates.CurrentGameState.Logo)
            this.logo.Load(this.Content, this.GraphicsDevice);

        if (GameState == ScreenStates.CurrentGameState.Menu)
            this.menu.Load_Menu(GraphicsDevice, Content);

        if (logo.FadeOut_logo == true)
            GameState = ScreenStates.CurrentGameState.Menu;

        if (GameState == ScreenStates.CurrentGameState.CharactersChooser)
        this.choose_pets.Load_ChoosePet(this.Content, this.GraphicsDevice);
        // TODO: use this.Content to load your game content here
    }


    protected override void UnloadContent()
    {
        // TODO: Unload any non ContentManager content here
        //this.logo.Unload_logo(Content);
    }


    protected override void Update(GameTime gameTime)
    {

        // Allows the game to exit
        if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            this.Exit();

                    if (GameState == ScreenStates.CurrentGameState.Logo)
                logo.Update_logo(gameTime);


                    if (GameState == ScreenStates.CurrentGameState.CharactersChooser)
                    choose_pets.Update_petchoose(gameTime);

        // TODO: Add your update logic here

        base.Update(gameTime);
    }


    protected override void Draw(GameTime gameTime)
    {
        GraphicsDevice.Clear(Color.Black);

        spriteBatch.Begin();

                    if (GameState == ScreenStates.CurrentGameState.Logo)
                        logo.Draw(spriteBatch);

                    if (logo.FadeOut_logo == true)
                        menu.Draw_Menu(spriteBatch);

                    if (GameState == ScreenStates.CurrentGameState.CharactersChooser)
                        choose_pets.Draw_petChoose(spriteBatch);

        spriteBatch.End();
        base.Draw(gameTime);
    }
}
}

这个菜单给我带来了问题

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

    namespace Mochi_Mochi_Pets_Life
    {
class Menu0
{
    Texture2D Text2D_Background;
    Rectangle Rec_Background;

    Texture2D ButtonText2DPlay;
    Rectangle ButtonRecPlay;


    public void Load_Menu(GraphicsDevice Graphics_Menu, ContentManager Content_Menu)
    {
        Content_Menu.RootDirectory = "Content"; 

        Text2D_Background = Content_Menu.Load<Texture2D>("UI\\MenuBack");
        Rec_Background = new Rectangle(0, 0, Graphics_Menu.Viewport.Width,                 Graphics_Menu.Viewport.Height);

        ButtonText2DPlay = Content_Menu.Load<Texture2D>("UI\\Buttons\\New Games");
        ButtonRecPlay = new Rectangle(Graphics_Menu.Viewport.Width, 400, 150, 40);
    }


    public void Draw_Menu(SpriteBatch Spritebatch_Menu)
    {
        Spritebatch_Menu.Draw(Text2D_Background, Rec_Background, Color.White);
        Spritebatch_Menu.Draw(ButtonText2DPlay, ButtonRecPlay, Color.White);
    }
}
    }

好的，这是做的是，当我的标志褪色为==真，游戏状态跳转到主马努，但它永远不会发生错误，我会感谢你的帮助。

Answer 1

Loading_Menu从不被调用，因此纹理Text2D_Background总是为空。

您应该认识到，LoadContent只在游戏中被调用，所以比较游戏状态是无用的，因为只会加载Logo内容。

作为解决方案，您可以在initalization时加载所有内容，如果需要的内容之前没有加载，则可以在游戏状态更改时加载它。

Answer 2

我认为您的Text2D_Background是空的，这是因为您从不调用Load_Menu。您在gameState中签入LoadContent，它将返回false。

if (GameState == ScreenStates.CurrentGameState.Menu)

LoadContent只被调用一次，我不明白为什么要检查gameState值。