Only one bullet on the screen. How can I fix this?

Question

I want that every enemy shoots independently a bullet. If an enemy’s bullet has left the screen, the enemy can shoot a new bullet. Not earlier. But for the moment, their always is just one bullet on the screen instead of three. I have three enemies, so their could be a maximum of three bullets simultaneously on the screen and not just one. What is wrong?

public class Map
{
    Texture2D myEnemy, myBullet;
    Player Player;
    List<Enemy> enemieslist = new List<Enemy>();
    List<Bullet> bulletslist = new List<Bullet>();

    float fNextEnemy = 0.0f;
    float fEnemyFreq = 3.0f;
    int fMaxEnemy = 3;

    Vector2 Startposition = new Vector2(200, 200);
    Vector2 currentEnemyPosition;

    GraphicsDeviceManager graphicsDevice; 

    public Map(GraphicsDeviceManager device) 
    { 
        graphicsDevice = device;

    } 

    public void Load(ContentManager content)
    {
    myEnemy = content.Load<Texture2D>("enemy");
    myBullet = content.Load<Texture2D>("bullet"); 
    Player = new Player(graphicsDevice);
    Player.Load(content);
    }

    public void Update(GameTime gameTime)
    {
        Player.Update(gameTime);
        float delta = (float)gameTime.ElapsedGameTime.TotalSeconds;

         for(int i = enemieslist.Count - 1; i >= 0; i--) 
        {
        // Update Enemy
        Enemy enemy = enemieslist[i];
        enemy.Update(gameTime, this.graphicsDevice, Player.playershape.Position, delta);
        currentEnemyPosition = enemy.Bulletstartposition;
        // Try to remove an enemy
        if (enemy.Remove == true)
        {
            enemieslist.Remove(enemy);
            enemy.Remove = false;
        }

        // Does the enemy shot?
        if ((enemy.Shot == true) && (bulletslist.Count < 1))
        // New bullet
          {
          Vector2 bulletDirection = Vector2.Normalize(Player.playershape.Position - currentEnemyPosition) * 200f;
          bulletslist.Add(new Bullet(currentEnemyPosition, bulletDirection, Player.playershape.Position));
          enemy.Shot = false;
          }
        }

        this.fNextEnemy += delta;
        //New enemy
        if (fMaxEnemy > 0)
        {
        if ((this.fNextEnemy >= fEnemyFreq) && (enemieslist.Count < 3))
        {
            Vector2 enemyDirection = Vector2.Normalize(Player.playershape.Position - Startposition) * 100f;
            enemieslist.Add(new Enemy(Startposition, enemyDirection, Player.playershape.Position));
            fMaxEnemy -= 1;
            fNextEnemy -= fEnemyFreq;
        }
        }

    for(int i = bulletslist.Count - 1; i >= 0; i--) 
    {
        // Update Bullet
        Bullet bullets = bulletslist[i];   
        bullets.Update(gameTime, this.graphicsDevice, delta);

        // Try to remove a bullet... Collision, hit, or outside screen.
        if (bullets.Remove == true)
            bulletslist.Remove(bullets);
        bullets.Remove = false;
    }              
  }

    public void Draw(SpriteBatch batch)
    {

        Player.Draw(batch);
        foreach (Enemy enemies in enemieslist)
        {
            enemies.Draw(batch, myEnemy);
        } 
        foreach (Bullet bullets in bulletslist)
        {
            bullets.Draw(batch, myBullet);
        } 
    }      
}

public class Enemy
{
 private float nextShot = 0;
 private float shotFrequency = 2.0f;  

    Vector2 vPos;
    Vector2 vMove;
    Vector2 vPlayer;
    public Vector2 Bulletstartposition;
    public bool Remove;
    public bool Shot;

    public Enemy(Vector2 Pos, Vector2 Move, Vector2 Player)
    {
        this.vPos = Pos;
        this.vMove = Move;
        this.vPlayer = Player;
        this.Remove = false;
        this.Shot = false;
    }

    public void Update(GameTime gameTime, GraphicsDeviceManager graphics, Vector2 PlayerPos, float delta)
    {           
        nextShot += delta;

        if (nextShot >= shotFrequency)
            {
            this.Shot = true;
            nextShot -= shotFrequency;
            }

        if (!Remove)
        {
            this.vMove = Vector2.Normalize(PlayerPos - this.vPos) * 100f;
            this.vPos += this.vMove * delta;
            Bulletstartposition = this.vPos;

            if (this.vPos.X > graphics.PreferredBackBufferWidth + 1)
            {
                this.Remove = true;
            }

            else if (this.vPos.X < -20)
            {
                this.Remove = true;
            }

            if (this.vPos.Y > graphics.PreferredBackBufferHeight + 1)
            {
                this.Remove = true;
            }

            else if (this.vPos.Y < -20)
            {
                this.Remove = true;
            }
        }
    }

    public void Draw(SpriteBatch spriteBatch, Texture2D myTexture)
    {
        if (!Remove)
        {
            spriteBatch.Draw(myTexture, this.vPos, Color.White);
        }
    }
}

public class Bullet
{
    Vector2 vPos;
    Vector2 vMove;
    Vector2 vPlayer;
    public bool Remove;

    public Bullet(Vector2 Pos, Vector2 Move, Vector2 Player)
    {
        this.Remove = false;
        this.vPos = Pos;
        this.vMove = Move;
        this.vPlayer = Player;
    }

    public void Update(GameTime gameTime, GraphicsDeviceManager graphics, float delta)
    {
            if (!Remove)
            {
                this.vPos += this.vMove * delta;                  

                if (this.vPos.X > graphics.PreferredBackBufferWidth +1)
                {
                    this.Remove = true;
                }

                else if (this.vPos.X < -20)
                {
                    this.Remove = true;
                }

                if (this.vPos.Y > graphics.PreferredBackBufferHeight +1)
                {
                    this.Remove = true;
                }

                else if (this.vPos.Y < -20)
                {
                    this.Remove = true;
                }
            }         
    }

    public void Draw(SpriteBatch spriteBatch, Texture2D myTexture)
    {
        if (!Remove)
        {
            spriteBatch.Draw(myTexture, this.vPos, Color.White);
        }
    }
}

Answer 1

You need to associate each enemy with the bullet it shot. Easiest is to add a field to the Enemy-class of type Bullet, and a field of type Enemy to the Bullet-class.

(If you want a more decoupled approach, you could create an interface IFireBullet)

Instead of checking if the number of bullets is less than one, you check if the enemy has an active bullet.

// Does the enemy shot?
if ((enemy.Shot == true) && (enemy.Bullet == null))
{
    …
}

And don't forget to clear the field when the bullet flies off screen. (This is where the Enemy-field is helpful.)