Time for action - updating and drawing the StarField

  1. Add the Update() and Draw() methods to the StarField class:
    public void Update(GameTime gameTime)
{
foreach (Sprite star in stars)
{
star.Update(gameTime);
if (star.Location.Y > screenHeight)
{
star.Location = new Vector2(
rand.Next(0, screenWidth), 0);
}
}
}
public void Draw(SpriteBatch spriteBatch)
{
foreach (Sprite star in stars)
{
star.Draw(spriteBatch);
}
}

What just happened?

When the star field needs to be updated, a foreach loop processes each item in the stars list, running the sprite's Update() method. The method then checks the star's Location property's Y component to determine if the star has moved off the bottom of the screen. If it has, the star is assigned a new Location with a random X component and a Y component of zero, placing the star at a random location along the top of the screen.

The StarField.Draw() method simply passes along the spriteBatch object to each of the individual stars in the stars list and instructs them to draw themselves.

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