Repeatedly Shooting Bullets

Question

I'm making an XNA shooter game. How do I have my sprite repeatedly shoot bullets instead of waiting for one bullet to go off the screen. Do I do this with and array?

Answer 1

I imagine somewhere you have: Bullet bullet;

Then some methods such as:

ShootBullet(int x, int y)
{
  Bullet b = new Bullet(x, y);
}

Draw()
{
  b.Draw(SpriteBatch); //or SpriteBatch.Draw(b.tex, b.bounds, b.x, b.y)
}

Update()
{
    b.Update(); //or b.X += b.xAccel
}

Because of this, you are only allowing yourself one bullet at a time. What you want to do, since I imagine you aren't looking for the most efficient method, is to do the following.

List<Bullet> bulletsOnScreen;

In your constructor put:

bulletsOnScreen = new List<Bullet>();

Then do the following:

ShootBullet(x,y)
{
  Bullet b = new Bullet(x,y);
  bulletsOnScreen.Add(b);
}

Draw()
{
  foreach(Bullet b in bulletsOnScreen)
    b.Draw();
}

Update()
{
  foreach(Bullet b in bulletsOnScreen)
    b.Update();

  if(b.bounds.X > screen.X) //add more logic for being off screen
    bulletsOnScreen.Remove(b);
}

This will maintain a list of bullets you can keep track of, and when the bullet is no longer on screen (this is where you need to put in logic to determine if a bullet is off screen) it removes it from the list of bullets.

Answer 2

You could create a timer class, then invoke the timer so when it's finished, the timer allows the next bullet to be shot.

I'm pretty sure this would work Create a separate class named Timer and put this in it.

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

namespace (your namespace) {
class Timer
    {
        int TimeToDelay;
        int TimeElapsed;
        public bool IsTimerDone;

        public void StartTimer(GameTime gt, int AmountOfTime)
        {
            while (AmountOfTime < TimeElapsed)
            {
                IsTimerDone = false;
                TimeToDelay = AmountOfTime;
                if (IsTimerDone == false)
                {
                    if (TimeToDelay == gt.ElapsedGameTime.TotalSeconds)
                    {
                        IsTimerDone = true;

                    }
                    else TimeElapsed += 1;
                }
            }
        }
    }
}

Then Invoke the timer class in the main game class.

namespace (GameNameHere)
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

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

        /* DECLARE INIT VARIABLES */
    // Declare Timer
        Timer timer;
    Bool BulletReady = true;    

        protected override void Initialize()
        {
            /* Init logic */

        // Create New Instance of The Timer     
        timer = new Timer();        

            base.Initialize();
        }

        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);


        }

        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();

            // REPLACE CONTROL CODE WITH INVOKE/BUTTONPRESS HERE
            // if (GamePad.GetState(PlayerIndex.One).Buttons.A == ButtonState.Pressed)
            // {
                if (BulletReady == true)
                {
                    if (timer.IsTimerDone == false)
                    {
                        // replace 1 with amount of time (in seconds)
                        timer.StartTimer(gameTime, 1);
                        BulletReady = false;
                    }
                    else if (timer.IsTimerDone == true)
                    {
                        BulletReady = true;
                    }

                }

                }
            // }


            // 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

            base.Draw(gameTime);
        }
    }
}

The bulletready boolean value is for so you can shoot again. If it is true, You can shoot, vice versa.

Basically, for the invoke, Create the timer's variable, Create a new instance in the initialization, Then in update, check for gamepad input, and if the bulletready is true, start a timer for the amount of time you want the bullet to be on cool down.