source: 2011/23/sijoseha/Fera Proelia/Fera Proelia/Fera Proelia/ScreenManager.cs @ 2119

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

namespace Fera_Proelia
{
    public class ScreenManager : DrawableGameComponent
    {
        List<GameScreen> screens = new List<GameScreen>();
        List<GameScreen> screensToUpdate = new List<GameScreen>();

        SpriteBatch spriteBatch;

        bool isInitialized;

        public SpriteBatch SpriteBatch { get { return spriteBatch; } }

        public ScreenManager(Game game)
            : base(game)
        {
        }

        public override void Initialize()
        {
            base.Initialize();
            isInitialized = true;
        }

        protected override void LoadContent()
        {
            ContentManager content = Game.Content;
            spriteBatch = new SpriteBatch(GraphicsDevice);

            foreach (GameScreen screen in screens)
            {
                screen.LoadContent();
            }
        }

        protected override void UnloadContent()
        {
            foreach (GameScreen screen in screens)
            {
                screen.UnloadContent();
            }
        }

        public override void Update(GameTime gameTime)
        {
            screensToUpdate.Clear();
            foreach (GameScreen screen in screens)
                screensToUpdate.Add(screen);

            bool otherScreenHasFocus = !Game.IsActive;

            while (screensToUpdate.Count > 0)
            {
                GameScreen screen = screensToUpdate[screensToUpdate.Count - 1];
                screensToUpdate.RemoveAt(screensToUpdate.Count - 1);

                screen.Update(gameTime, otherScreenHasFocus);
            }

            base.Update(gameTime);
        }

        public override void Draw(GameTime gameTime)
        {
            foreach (GameScreen screen in screens)
            {
                screen.Draw(gameTime);
            }
            base.Draw(gameTime);
        }
    }
}