XNA - Rectangle Error

Question

im working on a pong game, and im trying to make so when the ball collides the paddle, it bounces off..as simple as that. But when i use rectangles, cus i think using if(ballRect.Intersects(gPaddle.gRect)) is the best way of making a collision. But when i start my game, everything goes wrong, the ball dissappears, and the paddle textures gets wierd, a part of it doesnt follow the paddle and yeah.. heres the code:

GreenPaddle.cs:

    public class GreenPaddle
{
    public Texture2D gPtexture;
    public Vector2 position;
    public Rectangle gpRect;
    public Vector2 origin;
    public int speed = 2;

    public GreenPaddle()
    {

    }

    public void LoadContent(ContentManager Content)
    {
        gPtexture = Content.Load<Texture2D>("greenpaddle");
        position = new Vector2(20, 200);
        gpRect = new Rectangle((int)position.X, (int)position.Y,
            gPtexture.Width, gPtexture.Height);
    }

    public void Update(GameTime gameTime)
    {
        KeyboardState keyState = Keyboard.GetState();

        //Movement
        PaddleMovement();

        //Border Collision
        isCollidingWithBorders();
      }

    public void Draw(SpriteBatch spriteBatch)
    {
        spriteBatch.Draw(gPtexture, position, gpRect, Color.White);
    }

    public Boolean isCollidingWithBorders()
    {
        if (position.Y < 83 && gpRect.Y < 83)
        {
            position.Y = 83;
            gpRect.Y = 83;
            return true;
        }

        if (position.Y > 400 && gpRect.Y > 400)
        {
            position.Y = 400;
            gpRect.Y = 400;
            return true;
        }

        else { return false; }

    }

    public void PaddleMovement()
    {
        KeyboardState keyState = Keyboard.GetState();
        if (keyState.IsKeyDown(Keys.W))
        {
            position.Y -= speed;
            gpRect.Y -= speed;
        }
        if (keyState.IsKeyDown(Keys.S))
        {
            position.Y += speed;
            gpRect.Y += speed;
        }
    }
}

Ball.cs:

 public class Ball
{
    GreenPaddle gPaddle = new GreenPaddle();

    Texture2D ballTexture;
    Vector2 ballPosition;
    Rectangle ballRect;
    int speed = 2;
    bool movingUp, movingLeft;

    public Ball()
    {
        movingLeft = true;
        movingUp = true;
    }

    public void LoadContent(ContentManager Content)
    {
        ballTexture = Content.Load<Texture2D>("ball");
        ballPosition = new Vector2(380, 225);
        ballRect = new Rectangle((int)ballPosition.X, (int)ballPosition.Y,
            ballTexture.Width, ballTexture.Height);

    }

    public void Update(GameTime gameTime)
    {
        BallMovement();

    }

    public void Draw(SpriteBatch spriteBatch)
    {
        spriteBatch.Draw(ballTexture, ballPosition, ballRect, Color.White);
    }

    public void BallMovement()
    {
        if (movingUp) { ballPosition.Y -= speed; ballRect.Y -= speed; }
        if (!movingUp) { ballPosition.Y += speed; ballRect.Y += speed; }
        if (movingLeft) { ballPosition.X -= speed; ballRect.X -= speed; }
        if (!movingLeft) { ballPosition.X += speed; ballRect.X += speed; }

        if (ballRect.Intersects(gPaddle.gpRect))
            movingLeft = false;

        if (ballPosition.Y < 85)
        {
            movingUp = false;
        }
    }
}

Game1.cs:

public class Game1 : Microsoft.Xna.Framework.Game
{
    GraphicsDeviceManager graphics;
    SpriteBatch spriteBatch;


    Texture2D BackGround;
    GreenPaddle gPaddle = new GreenPaddle();
    Ball ball = new Ball();

    public Game1()
    {
        graphics = new GraphicsDeviceManager(this);
        Content.RootDirectory = "Content";
        graphics.PreferredBackBufferHeight = 500;
    }

    protected override void Initialize()
    {
        // TODO: Add your initialization logic here

        base.Initialize();
    }

    /// <summary>
    /// LoadContent will be called once per game and is the place to load
    /// all of your content.
    /// </summary>
    protected override void LoadContent()
    {
        // Create a new SpriteBatch, which can be used to draw textures.
        spriteBatch = new SpriteBatch(GraphicsDevice);

        BackGround = Content.Load<Texture2D>("pongBG");
        gPaddle.LoadContent(Content);
        ball.LoadContent(Content);
    }

    /// <summary>
    /// UnloadContent will be called once per game and is the place to unload
    /// all content.
    /// </summary>
    protected override void UnloadContent()
    {
        // TODO: Unload any non ContentManager content here
    }

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

        gPaddle.Update(gameTime);
        ball.Update(gameTime);

        base.Update(gameTime);
    }

    /// <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)
    {
        GraphicsDevice.Clear(Color.CornflowerBlue);

        spriteBatch.Begin();
        spriteBatch.Draw(BackGround, new Vector2(0f, 0f), Color.White);
        gPaddle.Draw(spriteBatch);
        ball.Draw(spriteBatch);
        spriteBatch.End();

        base.Draw(gameTime);
    }
}

What should i do? What am i missing? Thanks in advance :)

Answer 1

The collision test is inside the Ball class. In it you are testing whether the ball collides with a private member of the class called gPaddle, NOT the one that your game uses and that you update and draw.

Replace

GreenPaddle gPaddle = new GreenPaddle();

with

GreenPaddle gPaddle;
...
public Ball(GreenPaddle paddle)
{
     this.gPaddle = paddle;      
}

Also, don't use 2 booleans and a scalar to denote velocity. Use a Vector2. Your BallMovement method is wrong as well. You should reflect the ball upon intersection in the paddle which means to reverse its direction in BOTH x and y axes:

With 2 bools:

    if (ballRect.Intersects(gPaddle.gpRect))
     {
          movingLeft = !movingLeft
          movingTop = !movingTop;
     }

With a Vector2 as speed:

     if (ballRect.Intersects(gPaddle.gpRect))
     {
          velocity = -velocity;
     }