Question

I am trying to implement a simple counter in my XNA game. Thought this would be simple enough. I have the following code:

    elapsed = gameTime.ElapsedGameTime.TotalMilliseconds;
        timer -= (int)elapsed;

        if (timer <= 0)
        {
            timer = 10;   //Reset Timer
        }

But elapsed never changes from 0.0. Am I missing something obvious here? I suspect I am. I have gameTime declared at the top and initialised as usual.

As asked, here is a bit more code:

public class Game1 : Microsoft.Xna.Framework.Game
{

private GameTime zombieTime; 



    public Game1()
    {
        zombieTime = new GameTime();
        // Other (unrelated) stuff here
    }



    protected void AddZombie()
    {
        elapsed = zombieTime.ElapsedGameTime.TotalMilliseconds;
        timer -= (int)elapsed;

        if (timer <= 0)
        {
            timer = 10;   //Reset Timer
            Zombie zombie = new Zombie(ScreenWidth, ScreenHeight, random);
            zombie.LoadContent(this.Content, "ZombieSprites/ZombieLeft1");
            zombies.Insert(0, zombie);
        }
     }

    protected void Update()
    {
        AddZombie();
        // Other game update stuff here
    }
}

I am sorry, I believed the original code snippet would have been enough. I read some pages online where people posted examples of a timer and used the method I have used above. I understand some of the comments made here about the update going fast enough so that elapsed time will always be 0.

Answer 1

You’re not using the correct GameTime. zombieTime is never updated by anything so it will always be zero’d out. The GameTime you want to use is passed into the Update() function already for you.

The correct way to do it would be like this:

protected void AddZombie(GameTime gameTime)
{
    float elapsed = gameTime.ElapsedGameTime.TotalMilliseconds;
    timer -= (int)elapsed;

    if (timer <= 0)
    {
        timer = 10;   //Reset Timer
        // Rest of stuff goes here
    }
}

protected void Update(GameTime gameTime)
{
    AddZombie(gameTime);
}