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C# ArgumentNullException was unhandled (SpriteBatch.Draw)

I am actually a new student in XNA, finding this library very interesting, but I still lack some knowledge to go further as I felt on a issue I can't fix on my own :(
The spriteBatch.Draw() method says my texture is null, however I have loaded it in a Resources.cs class and passed the texture in MainMenu.cs, so I don't really know where the problem resides, if anybody could help me about that I would be very thankful !
Resources.cs
class Resources
{
public static Texture2D pixel;
public static Texture2D startButton, loadButton, quitButton;
public static SpriteFont consoleFont;
public static void LoadContent(ContentManager Content)
{
pixel = Content.Load<Texture2D>("Pixel");
consoleFont = Content.Load<SpriteFont>("Console");
// UI Ressources :
startButton = Content.Load<Texture2D>("UI/StartButton");
loadButton = Content.Load<Texture2D>("UI/LoadButton");
quitButton = Content.Load<Texture2D>("UI/QuitButton");
}
}
MainMenu.cs
class MainMenu
{
// Fields
List<Button> buttons = new List<Button>();
// Constructors
public MainMenu()
{
this.buttons.Add(new Button(new Vector2(480, 132), 256, 48, Resources.startButton));
this.buttons.Add(new Button(new Vector2(480, 212), 256, 48, Resources.loadButton));
this.buttons.Add(new Button(new Vector2(480, 292), 256, 48, Resources.quitButton));
}
// Methods
// Update
public void Update()
{
}
// Draw
public void Draw(SpriteBatch spriteBatch)
{
foreach (Button button in buttons)
{
button.Draw(spriteBatch);
}
}
}
Button.cs
class Button : UIElement
{
int width, height;
Texture2D texture;
public Button()
{
}
public Button(Vector2 b_position, int b_width, int b_height, Texture2D b_texture)
{
this.position = b_position;
this.width = b_width;
this.height = b_height;
this.texture = b_texture;
}
public void Update()
{
}
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(texture, position, Color.White);
}
}

Simple realy
You just have to know the calling order of functions of Game1. First, Game1 constructor is called. That's where you've put mainMenu = new MainMenu();. After that go Initialize, Load and so on. You have to move mainMenu = new MainMenu(); from Game1 constructor to Load function, after the Resources.LoadContent(Content);, so the resources can be loaded before they are used in MainMenu. Your Game1.cs code should look like this:
public class GameMain : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
MainMenu mainMenu;
public GameMain()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
this.IsMouseVisible = true;
}
protected override void Initialize()
{
// TODO: Add your initialization logic here
base.Initialize();
}
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
Resources.LoadContent(Content);
mainMenu = new MainMenu();
}
protected override void UnloadContent()
{
// TODO: Unload any non ContentManager content here
}
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
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
// TODO: Add your drawing code here
spriteBatch.Begin();
mainMenu.Draw(spriteBatch);
spriteBatch.End();
base.Draw(gameTime);
}
}

While I do not see your Game class my first assumption is that your never calling the public static void LoadContent(ContentManager Content) method inside your Resources class. Since this function is instantiating your textures perhaps this isn't being called.

Thank you for your reply !
Indeed I forgot to include the Game class, is this the right way to call the resources ?
public class GameMain : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
MainMenu mainMenu;
public GameMain()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
this.IsMouseVisible = true;
mainMenu = new MainMenu();
}
protected override void Initialize()
{
// TODO: Add your initialization logic here
base.Initialize();
}
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
Resources.LoadContent(Content);
}
protected override void UnloadContent()
{
// TODO: Unload any non ContentManager content here
}
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
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
// TODO: Add your drawing code here
spriteBatch.Begin();
mainMenu.Draw(spriteBatch);
spriteBatch.End();
base.Draw(gameTime);
}
}

C# XNA Add a GameComponent from within a GameComponent

public class Menu : DrawableGameComponent
{
ContentManager Content;
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Audio MenuMusic;
public Menu(Game game) : base(game)
{
spriteBatch = Game.Services.GetService(typeof(SpriteBatch)) as SpriteBatch;
graphics = Game.Services.GetService(typeof(GraphicsDeviceManager)) as GraphicsDeviceManager;
Content = game.Content;
Content.RootDirectory = #"Content\Menu\";
*MenuMusic = new Audio(game);* // Instantiate the new DrawableGameComponent
Game.Components.Add(this);
MenuMusic.PauseTune = false;
}
public override void Initialize()
{
Menustate = MenuState.LoadContent;
base.Initialize();
}
protected override void LoadContent()
{
base.LoadContent();
}
protected override void UnloadContent()
{
base.UnloadContent();
}
public override void Update(GameTime gameTime)
{
base.Update(gameTime);
}
public override void Draw(GameTime gameTime)
{
base.Draw(gameTime);
}
}
public class Audio : DrawableGameComponent
{
public bool PauseTune
{
get { return PauseTune; }
set { PauseTune = value; }
}
SoundEffect Tune = null;
SoundEffectInstance SFXInstance;
public Audio(Game game) : base(game)
{
*game.Components.Add(this)*;// This is the problem. It adds an entirely new Game object. :(
}
public override void Initialize()
{
PauseTune = true;
base.Initialize();
}
protected override void LoadContent()
{
switch (Game1.Gamestate)
{
case GameState.Menu:
string AudioPath = #"Audio\";
Tune = Game.Content.Load<SoundEffect>(AudioPath + "Tune");
break;
case GameState.InitialiseGame:
break;
case GameState.PlayGame:
break;
default:
break;
}
if (Tune != null) SFXInstance = Tune.CreateInstance();
base.LoadContent();
}
protected override void UnloadContent()
{
base.UnloadContent();
}
public override void Update(GameTime gameTime)
{
if (Tune != null)
{
if (PauseTune)
{
if (SFXInstance.State == SoundState.Playing)
SFXInstance.Pause();
}
else
{
if (SFXInstance.State != SoundState.Playing)
SFXInstance.Play();
}
}
base.Update(gameTime);
}
public override void Draw(GameTime gameTime)
{
base.Draw(gameTime);
}
}
The probelem comes when I use the Menu to add a new Audio class instance.
The Audio constructor attempts to add the new GameCompent but fails.
What it actually does is create an entirely new Game instance, which then goes on to instantiate a new Menu that attempts to add a new Audio class instance..... Until I eventually get a - would you beleive? - stackoverflow error.
What am I doing wrong? / How can I add one component from within another?

DOH! Some days I should never turn on my computer :)
Or better yet - after a long, tiring day do NOT mess with mycode.
A self-referencing PauseTune property.

XNA Sprite doesn't seem to be updating?

I've looked through some other questions and haven't found my answer so I'm asking you lovely people as you have helped me before :)
I have a main class (RPG.cs) and a player class (Player.cs) and I want the Player class to be as self-contained as possible (because I don't want a huuuge main class) but here is my problem.
Problem
My Player sprite draws fine but when I want it to move, it won't update! At the moment I'm attempting to make it act like a cursor to test movement but eventually I'll have it bound to WASD or the arrow keys. So I want my sprite to follow my mouse at the moment but it just stays at 50, 50 (it's preset starting position) Have I missed something obvious? I'm new to XNA and I've spent half an hour on this problem!
RPG.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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 TestGame
{
public class RPG : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Texture2D PlayerTex;
Rectangle playerPos = new Rectangle(
Convert.ToInt32(Player.Pos.X),
Convert.ToInt32(Player.Pos.Y), 32, 32);
public RPG()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
IsMouseVisible = true;
}
protected override void Initialize() { base.Initialize(); }
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
PlayerTex = Content.Load<Texture2D>("testChar");
}
protected override void UnloadContent() { }
protected override void Update(GameTime gameTime)
{
if
(
GamePad.GetState(PlayerIndex.One)
.Buttons.Back == ButtonState.Pressed
)
this.Exit();
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.White);
spriteBatch.Begin();
spriteBatch.Draw(PlayerTex, playerPos, Color.White);
spriteBatch.End();
base.Draw(gameTime);
}
}
}
Player.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 TestGame
{
/// This is a game component that implements IUpdateable.
public class Player : Microsoft.Xna.Framework.GameComponent
{
public static Vector2 Pos = new Vector2(50, 50);
MouseState ms = Mouse.GetState();
public Player(Game game) : base(game) { }
/// Allows the game component to perform
/// any initialization it needs to before
/// starting to run. This is where it can
/// query for any required services and load content.
public override void Initialize() { base.Initialize(); }
/// Allows the game component to update itself.
public override void Update(GameTime gameTime)
{
Pos.X = ms.X;
Pos.Y = ms.Y;
base.Update(gameTime);
}
}
}
Hope you can help! :)

As mentioned in the comment, I am not going to solve every problem. But the main errors.
Let the player be responsible for its position, not the game. Furthermore, I would make the player responsible for drawing itself, but that goes a bit too far for this answer.
The following code should at least work.
public class Player : Microsoft.Xna.Framework.GameComponent
{
public Vector2 Pos { get; set; }
public Player(Game game) : base(game)
{
this.Pos = new Vector2(50, 50);
}
public override void Initialize() { base.Initialize(); }
public override void Update(GameTime gameTime)
{
var ms = Mouse.GetState();
Pos.X = ms.X;
Pos.Y = ms.Y;
base.Update(gameTime);
}
}
Then use the player in your game:
public class RPG : Microsoft.Xna.Framework.Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
Texture2D PlayerTex;
Player player;
public RPG()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
IsMouseVisible = true;
player = new Player(this);
Components.Add(player);
}
protected override void Initialize() { base.Initialize(); }
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
PlayerTex = Content.Load<Texture2D>("testChar");
}
protected override void UnloadContent() { }
protected override void Update(GameTime gameTime)
{
if
(
GamePad.GetState(PlayerIndex.One)
.Buttons.Back == ButtonState.Pressed
)
this.Exit();
base.Update(gameTime);
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.White);
spriteBatch.Begin();
spriteBatch.Draw(PlayerTex, player.Pos, Color.White);
spriteBatch.End();
base.Draw(gameTime);
}
}
I have removed the texture's size. Don't know if you really need this. If so, you can let Player expose a Rectangle, not just a Vector2.

The key solution which Nico included is just that you using the original rectangle coordinates you made when you draw:
Rectangle playerPos = new Rectangle(
Convert.ToInt32(Player.Pos.X),
Convert.ToInt32(Player.Pos.Y), 32, 32);
Here you make the rectangle using the players CURRENT starting time position.
Then you ALWAYS draw based on this rectangle you made ages ago and never updated:
spriteBatch.Draw(PlayerTex, playerPos, Color.White);
The right way as Nico mentioned is just to change the draw to this:
playerPos = new Rectangle(
Convert.ToInt32(Player.Pos.X),
Convert.ToInt32(Player.Pos.Y), 32, 32);
spriteBatch.Draw(PlayerTex, playerPos, Color.White);
Now you will be drawing at a new place every time. There are better ways to do this (like what nico did) but here is the core idea.

Update a string based on key presses

I hope this isn't a stupid question but I cannot figure this out.
I have a barebones game class:
public class Game1 : Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
String inputHolder;
public Game1()
: base()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
inputHolder = "Enter your keys: ";
}
protected override void Initialize()
{
base.Initialize();
InputManager.stringToUpdate = inputHolder;
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
}
protected override void UnloadContent()
{
}
protected override void Update(GameTime gameTime)
{
if (Keyboard.GetState().IsKeyDown(Keys.Escape))
{
Exit();
}
base.Update(gameTime);
InputManager.update(Keyboard.GetState());
}
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
base.Draw(gameTime);
Console.WriteLine(inputHolder);
}
}
I also have an InputManager class:
static class InputManager
{
public static string stringToUpdate;
public static void update(KeyboardState kbState)
{
if (stringToUpdate != null)
{
foreach (Keys k in kbState.GetPressedKeys())
{
stringToUpdate += k.ToString();
}
}
}
}
However no matter what keys I press the original string inputHolder is not affected even though strings are treated as reference types in C#.
I have tried changing
InputManager.stringToUpdate = inputHolder;
to
InputManager.stringToUpdate = ref inputHolder;
and nothing happens.
What am I missing here?

As has already been said, strings are immutable. Wrapping the inputHolder string in a class will give you the desired effect:
public class InputHolder
{
public string Input { get; set; }
}
public class Game1 : Game
{
GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
InputHolder inputHolder = new InputHolder();
public Game1()
: base()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
inputHolder.Input = "Enter your keys: ";
}
protected override void Initialize()
{
base.Initialize();
InputManager.inputHolderToUpdate = inputHolder;
}
// etc
protected override void Draw(GameTime gameTime)
{
GraphicsDevice.Clear(Color.CornflowerBlue);
base.Draw(gameTime);
Console.WriteLine(inputHolder.Input);
}
}
static class InputManager
{
public static InputHolder inputHolderToUpdate;
public static void update(KeyboardState kbState)
{
if (inputHolderToUpdate != null)
{
foreach (Keys k in kbState.GetPressedKeys())
{
inputHolderToUpdate.Input = inputHolderToUpdate.Input + k.ToString();
}
}
}
}

xna Loading content from a non GameComponent class

I am a relative beginner in XNA and am trying to create a screenManager for an C# XNA game. Everything in my code seems to work fine until I reach the LoadContent method in my MainMenu class which derives from Screen which is a custom standalone class. This is where I get my GraphicsDevice component not found ContentLoad exception.
This is on the the statement: texture = c.Load<Texture2D>("Textures/Start");
where c is a ContentManager.
This statement and the program works okay if I put it in the Update method of my class. However, I only want to load this texture once, not with each call to Update(GameTime). I think I must be calling load before some Content info is being initialized but I'm not sure what. There are some commented out statements in MainMenu.LoadContent that do pretty much the same thing and all produce the same error. I'm posting my entire code here. Hope it isn't flooding the forum.
Here's Game1.cs:
namespace RoomGame
{
/// <summary>
/// This is the main type for your game
/// </summary>
public class Game1 : Microsoft.Xna.Framework.Game
{
public static GraphicsDeviceManager graphics;
SpriteBatch spriteBatch;
GameController gameController;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
gameController = new GameController(this,this.Content);
this.Components.Add(gameController);
}
}
}
GameController.cs:
namespace RoomGame
{
public class GameController : DrawableGameComponent
{
public Game game;
public ContentManager content;
public ScreenController screenController;
public MainMenu menu;
public GameController(Game game,ContentManager c)
: base(game)
{
this.game = game;
content = c;
screenController = new ScreenController(this);
menu = new MainMenu(this,this.content);
screenController.AddScreen(menu);
}
public override void Initialize()
{
base.Initialize();
screenController.Initialize();
}
protected override void LoadContent()
{
base.LoadContent();
}
protected override void UnloadContent()
{
base.UnloadContent();
}
public override void Update(GameTime gameTime)
{
screenController.Update(gameTime);
base.Update(gameTime);
}
public override void Draw(GameTime gameTime)
{
base.Draw(gameTime);
screenController.Draw(gameTime);
}
}
}
screenController.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
namespace RoomGame
{
public class ScreenController
{
public List<Screen> screens = new List<Screen>();
GameController gameController;
SpriteBatch spriteBatch;
public ScreenController(GameController gc)
{
this.gameController = gc;
}
public void Initialize()
{
spriteBatch = new SpriteBatch(this.gameController.GraphicsDevice);
}
public void Update(GameTime gameTime)
{
foreach (Screen screen in screens)
{
if (screen.isUpdating)
screen.Update(gameTime);
}
}
public void Draw(GameTime gameTime)
{
foreach (Screen screen in screens)
{
if (screen.isDrawn)
{
spriteBatch.Begin();
screen.Draw(gameTime,spriteBatch);
spriteBatch.End();
}
}
}
public void AddScreen(Screen screen)
{
if (!screens.Contains(screen))
{
screen.LoadContent(this.gameController.game.Content);
screens.Add(screen);
//screen.Initialize();
}
}
}
}
Screen.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.Content;
namespace RoomGame
{
public class Screen
{
public ScreenController screenController;
public bool isUpdating=true;
public bool isDrawn=true;
public GraphicsDeviceManager graphics;
/*public Screen(ScreenController sc)
{
this.screenController = sc;
this.isActive = true;
}*/
public virtual void Initialize()
{ }
public virtual void LoadContent(ContentManager c)
{ }
public virtual void Update(GameTime gameTime)
{ }
public virtual void Draw(GameTime gameTime,SpriteBatch sb)
{ }
}
}
MainMenu.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.Content;
namespace RoomGame
{
public class MainMenu : Screen
{
GameController gameController;
Texture2D texture;
Vector2 position;
ContentManager content;
//public GraphicsDeviceManager graphics;
public MainMenu(GameController gc,ContentManager c)
{
this.gameController = gc;
this.content = c;
this.isUpdating = true;
this.isDrawn = true;
//this.graphics = this.gameController.game.graphics;
}
public override void LoadContent(ContentManager c)
{
texture = c.Load<Texture2D>("Textures/Start");
//texture = this.gameController.game.Content.Load<Texture2D>("Textures/Start");
//texture=this.gameController.content.Load<Texture2D>("Textures/Start");
//texture = this.gameController.Game.Content.Load<Texture2D>("Textures/Start");
}
public override void Update(GameTime gameTime)
{
//texture = this.gameController.content.Load<Texture2D>("Textures/Start");
position = new Vector2(100, 100);
}
public override void Draw(GameTime gameTime,SpriteBatch sb)
{
sb.Draw(texture, position, Color.White);
}
}
}
Thanks in advance....
EDIT
I found my error. I was calling ScreenController.Add before the LoadContent in GameController. I put it after the base.LoadContent in gameController and it works now. I hope this can help somebody but if anyone know a better way of approaching this please let me know.

You call MainMenu.LoadContent from the constructor of the ScreenController which in turn is called by the Game's constructor. LoadContent should be called at the appropriate time. So move the call to AddScreen to the LoadContent method of the GameController.