My bullet fails to move as it should

Question

I'm working on a small game, and as my title states, the bullet is not moving properly. When I click, it simply draws the bullet at the set position, and remains stationary. For some reason, the Update function of the bullet doesn't constantly run. So any help would be appreciated, thanks. Currently, I have two classes (not including the Game1.cs), which are: Bullet class and Humvee(player) class.

Here's the code for my Bullet class:

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

namespace Humvee
{
public class Bullet
{
    // Unique id assigned to each bullet
    int bullet_id;

    public bool bullet_active = false;

    // This declares the position of the bullet upon creation (is changed in constructor for debugging purposes)
    public Vector2 Position = new Vector2(400, 240);

    // This declares the direction of the bullet upon creation (not used for now)
    public Vector2 Direction = new Vector2(0, 0);

    // This declares the speed of the bullet upon creation (not used for now)
    public Vector2 Speed = new Vector2(0, 0);

    // Stores the touch location for each bullet
    public Vector2 Destination = new Vector2(0, 0);

    public Bullet()
    {
    }

    // Constructor that assigns each bullet a unique id, starting position, and a boolean to know whether it's active or not
    public Bullet(int id, Vector2 destination)
    {
        bullet_id = id;
        Position.X = 100;
        Position.Y = 240;
        Destination = destination;
    }

    public void Update(GameTime gameTime, Vector2 touch_location, Vector2 touch_direction)
    {
            // Finds the difference between the location of the touch and the bullet
            Vector2 speed_difference = new Vector2(0,0);
            speed_difference.X = Math.Abs(Destination.X - Position.X);
            speed_difference.Y = Math.Abs(Destination.Y - Position.Y);

            //Update the Sprite and change it's position based on the passed in speed, direction and elapsed time.
            Position += touch_direction * speed_difference * (float)gameTime.ElapsedGameTime.TotalSeconds;

    }

    //Draw the sprite to the screen
    public void Draw(SpriteBatch theSpriteBatch, Texture2D Bullet_Texture)
    {
        theSpriteBatch.Draw(Bullet_Texture, Position, Color.White);
    }
}
}

Here's the Humvee class:

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

namespace Humvee
{
class Humvee
{
    // Position of the player
    public Vector2 Position = new Vector2(400,240);

    // Will be used to assign a unique id to each bullet
    public int b_id = 1;

    Bullet testbullet = new Bullet();

    // It creates a new bullet and calls the Update function from Bullet class which causes the bullet to 'shoot'
    public void ShootBullet(GameTime gameTime, Vector2 touch_location, Vector2 touch_direction)
    {
        testbullet = new Bullet(1, touch_location);
        testbullet.bullet_active = true;
        testbullet.Update(gameTime, testbullet.Destination, touch_direction);

    }

    public void Update(GameTime gameTime, Vector2 touch_location, Vector2 touch_direction)
    {
        ShootBullet(gameTime, touch_location, touch_direction);   
    }


    //Draw the sprite to the screen
    public void Draw(SpriteBatch theSpriteBatch, Texture2D humveesprite, Texture2D bulletsprite)
    {
        testbullet.Draw(theSpriteBatch, bulletsprite);
        theSpriteBatch.Draw(humveesprite, new Vector2(400, 240), Color.White);

    }

}
}

And here's part of the Game1 class code:

Humvee testhumvee;

    // Stores the sprites of the objects
    Texture2D background;
    Texture2D bullet;
    Texture2D player;

    Vector2 touch_direction; // Stores the direction of the tap
    Vector2 touch_location; // Stores the location of the tap

    bool shoot_isactive = false;

protected override void Update(GameTime gameTime)
    {
        // Allows the game to exit
        if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            this.Exit();

        #region Touch code
        //Touch
        T_Collec = TouchPanel.GetState();
        foreach (TouchLocation tl in T_Collec)
        {
            while (TouchPanel.IsGestureAvailable)
            {
                GestureSample gesture = TouchPanel.ReadGesture();
                if (gesture.GestureType == GestureType.Tap)
                {
                    if (tl.Position.X > testhumvee.Position.X && tl.Position.Y > testhumvee.Position.Y)
                    {
                        touch_direction = new Vector2(1, 1);

                    }
                    else if (tl.Position.X < testhumvee.Position.X && tl.Position.Y > testhumvee.Position.Y)
                    {
                        touch_direction = new Vector2(-1, 1);
                    }
                    else if (tl.Position.X < testhumvee.Position.X && tl.Position.Y < testhumvee.Position.Y)
                    {
                        touch_direction = new Vector2(-1, -1); 
                    }
                    else if (tl.Position.X > testhumvee.Position.X && tl.Position.Y < testhumvee.Position.Y)
                    {
                        touch_direction = new Vector2(1, -1);
                    }

                    touch_location = tl.Position;
                    shoot_isactive = true;
                 }

            }
        #endregion

            // TODO: Add your update logic here
            if (shoot_isactive == true)
            {
                testhumvee.Update(gameTime, touch_location, touch_direction);
            }
            base.Update(gameTime);
        }
    }

Answer 1

There are a couple of issues with the layout that could be causing you confusion.

First up is that your Update() method of the Humvee seems to be a rather bad name as its not Updating so much as Shooting a bullet.

Second up is that you are never calling Update on the bullet object anywhere. I can gather that you may have wanted to do it at the start of the Bullet's Draw() method so that it will calculate its new position and then draw itself there. (While not important right now you may want to consider doing the Update elsewhere as you will generally only want to do Draw() specific code when drawing, but that is another matter all together).

Since you are seeing things I am going to assume that at least draw is being done and so my above comment would suffice to get the bullet moving as long as you also adhere to @Gajet's comments. You have seen

Position += firedDirection + velocity + elapsedTime;

as the way to update bullets, but you need to know that firedDirection is a vector and velocity and elapsedTime should be real values (floats or doubles, whatever you are using). So if you get very unexpected results that would be the next area to look into.

Answer 2

What you want to do is to inherit your Humvee and Bullet classes from DrawableGameComponent, then add them to the Game.Components list as you create them.

This way Games base implementation of Update and Draw will call these methods for you, to fire a bullet you would call Humvee.ShootBullet directly and Humvee.Update method should no longer call ShootBullet (or you wind up firing a bullet every frame).

Add the following line to Humvee.ShootBullet:

Game.Components.Add(testbullet);

Since this allows you to fire any number of bullets you need to remove them from the Components collection at some point, like when they hit their target or go out of the game area/screen.

Answer 3

Your architecture and you code are flawed.

You forget to update existing bullets. The bullet is updated only through your humvee::update. And each time you update your humvee you shoot a new one.

When you stop updating your humvee you stop updating the last bullet...

You need to update all bullets from somewhere else.