I'm learning to program in C# using monodevelop and monogame. I'm fairly familiar with C and Java but in honesty, I'm still learning to think like an Object Oriented programmer. I wanted to use the following class to gather together relevant attributes of a sprite, together with methods to move, draw, accelerate, detect collisions etc. to tidy up the game code. This class appears in a file SpriteObject.cs and compiles without errors on build.
namespace MyFirstGame
{
class SpriteObject
{
private Texture2D Texture;
private Vector2 Position;
private Vector2 Velocity;
public SpriteObject(Texture2D texture, Vector2 position)
{
this.Texture = texture;
this.Position = position;
this.Velocity = Vector2.Zero;
}
public SpriteObject(Texture2D texture, Vector2 position, Vector2 velocity)
{
this.Texture = texture;
this.Position = position;
this.Velocity = velocity;
}
public Rectangle BoundingBox
{
get
{
return new Rectangle(
(int)Position.X,
(int)Position.Y,
Texture.Width,
Texture.Height);
}
}
public void Move(SpriteObject sprite)
{
this.Position += this.Velocity;
}
public void BounceX(SpriteObject sprite)
{
this.Velocity.X *= -1;
}
public void BounceY(SpriteObject sprite)
{
this.Velocity.Y *= -1;
}
public void Draw(SpriteBatch spriteBatch)
{
spriteBatch.Draw(Texture, Position, Color.White);
}
}
}
I'm am trying to use this class in the following code (which is a bastard mix of the untidy, but running, code I'm trying to clean up and the new class I'm trying to do it with). Note particularly the lines marked with A> and B>.
namespace MyFirstGame
{
/// <summary>
/// This is the main type for your game
/// </summary>
public class Game1 : Game
{
GraphicsDeviceManager graphics; // All default to private
KeyboardState oldKeyState;
SpriteBatch spriteBatch;
Boolean gameOn=true;
A> SpriteObject ballSprite, starSprite; // A couple of sprites...
Texture2D texStar, texBall; // This is a texture we can render.
public Game1()
{
graphics = new GraphicsDeviceManager(this);
graphics.PreferredBackBufferHeight = 900-32; // Force window size or it won't work...
graphics.PreferredBackBufferWidth = 1600; // Force window size
Content.RootDirectory = "Content";
graphics.IsFullScreen = true;
}
/// <summary>
/// Allows the game to perform any initialization it needs to before starting to run.
/// This is where it can query for any required services and load any non-graphic
/// related content. Calling base.Initialize will enumerate through any components
/// and initialize them as well.
/// </summary>
protected override void Initialize()
{
// TODO: Add your initialization logic here
oldKeyState = Keyboard.GetState();
base.Initialize();
}
/// <summary>
/// LoadContent will be called once per game and is the place to load
/// all of your content.
/// </summary>
// Set the coordinates to draw the sprite at.
Vector2 starPosition = Vector2.Zero;
Vector2 ballPosition = new Vector2(200, 0);
// Store some information about the sprite's motion.
Vector2 starSpeed = new Vector2(10.0f, 10.0f);
Vector2 ballSpeed = new Vector2(10.0f, 0.0f);
protected override void LoadContent()
{
// Create a new SpriteBatch, which can be used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);
texStar = Content.Load<Texture2D>("star");
texBall = Content.Load<Texture2D>("ball");
B> ballSprite = new SpriteObject(texBall, Vector2(200, 0), Vector2(10.0f, 0.0f)); // create two sprites
B> starSprite = new SpriteObject(texStar, Vector2.Zero, Vector2(10.0f, 10.0f));
}
/// <summary>
/// Allows the game to run logic such as updating the world,
/// checking for collisions, gathering input, and playing audio.
/// </summary>
/// <param name="gameTime">Provides a snapshot of timing values.</param>
protected override void Update(GameTime gameTime)
{
// Move the sprite by speed.
KeyboardState newKeyState = Keyboard.GetState();
if (newKeyState.IsKeyDown(Keys.Escape))
Exit();
if (collisionDetected()) gameOn = false; // If there's a collision then no movement.
//Could do with putting this in a seperate method or class, if there isn't one already...
if (gameOn)
{
if (newKeyState.IsKeyDown(Keys.PageUp) && oldKeyState.IsKeyUp(Keys.PageUp))
{
starSpeed.X *= 1.1f;
starSpeed.Y *= 1.1f;
}
else if (newKeyState.IsKeyDown(Keys.PageDown) && oldKeyState.IsKeyUp(Keys.PageDown))
{
starSpeed.X *= 0.9f;
starSpeed.Y *= 0.9f;
}
else if (newKeyState.IsKeyDown(Keys.Up) && oldKeyState.IsKeyUp(Keys.Up))
{
starSpeed.Y += 1.0f;
}
else if (newKeyState.IsKeyDown(Keys.Down) && oldKeyState.IsKeyUp(Keys.Down))
{
starSpeed.Y -= 1.0f;
}
else if (newKeyState.IsKeyDown(Keys.Left) && oldKeyState.IsKeyUp(Keys.Left))
{
starSpeed.X -= 1.0f;
}
else if (newKeyState.IsKeyDown(Keys.Right) && oldKeyState.IsKeyUp(Keys.Right))
{
starSpeed.X += 1.0f;
}
oldKeyState = newKeyState;
starPosition += starSpeed;
ballPosition += ballSpeed;
int MaxX =
graphics.GraphicsDevice.Viewport.Width - texStar.Width;
int MinX = 0;
int MaxY =
graphics.GraphicsDevice.Viewport.Height - texStar.Height;
int MinY = 0;
// Check for ball bounce
if (ballPosition.X > MaxX)
{
ballPosition.X = MaxX;
ballSpeed.X *= -1;
}
if (ballPosition.X < MinX)
{
ballPosition.X = MinX;
ballSpeed.X *= -1;
}
if (ballPosition.Y > MaxY)
{
ballSpeed.Y *= -1;
ballPosition.Y = MaxY;
}
ballSpeed.Y += 1;
// Check for bounce.
if (starPosition.X > MaxX)
{
starSpeed.X *= -1;
starPosition.X = MaxX;
}
else if (starPosition.X < MinX)
{
starSpeed.X *= -1;
starPosition.X = MinX;
}
if (starPosition.Y > MaxY)
{
starSpeed.Y *= -1;
starPosition.Y = MaxY;
}
else if (starPosition.Y < MinY)
{
starSpeed.Y *= -1;
starPosition.Y = MinY;
}
}
else
{
starSpeed=Vector2.Zero;
ballSpeed=Vector2.Zero;
}
}
private Boolean collisionDetected()
{
if (((Math.Abs(starPosition.X - ballPosition.X) < texStar.Width) && (Math.Abs(starPosition.Y - ballPosition.Y) < texBall.Height)))
{
return true;
}
else
{
return false;
}
}
/// <summary>
/// This is called when the game should draw itself.
/// </summary>
/// <param name="gameTime">Provides a snapshot of timing values.</param>
protected override void Draw(GameTime gameTime)
{
graphics.GraphicsDevice.Clear(Color.CornflowerBlue);
// Draw the sprite.
spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend);
spriteBatch.Draw(texStar, starPosition, Color.White);
spriteBatch.Draw(texBall, ballPosition, Color.White);
spriteBatch.End();
base.Draw(gameTime);
}
}
}
A> Marks where the new SpriteObject ballSprite, starSprite; are declared without any problems.
B> Marks where errors arise as I try to use the SpriteObject constructor to create and assign a value to my previously declared SpriteObjects - the errors as per the title of the post. Two such for the first line and one for the second.
The namespace hints at my level of experience with C#. If you could help me understand my almost certainly basic mistake I'd be very grateful.
Those two lines of code you indicated are missing the 'new' operator, which is required to instantiate the Vector2 (or any) class.
ballSprite = new SpriteObject(texBall, new Vector2(200, 0), new Vector2(10.0f, 0.0f));
starSprite = new SpriteObject(texStar, Vector2.Zero, new Vector2(10.0f, 10.0f));