source: 2011/23/sijoseha/Fera Proelia/Fera Proelia/Fera Proelia/ScreenManager.cs @ 2144

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

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

        InputState input = new InputState();

        SpriteBatch spriteBatch;
        SpriteFont menuFont, hudFont;

        bool isInitialized;

        public SpriteBatch SpriteBatch { get { return spriteBatch; } }
        public SpriteFont MenuFont { get { return menuFont; } }
        public SpriteFont HudFont { get { return hudFont; } }

        public ScreenManager(Game game)
            : base(game)
        {
            TouchPanel.EnabledGestures = GestureType.None;
        }

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

        protected override void LoadContent()
        {
            ContentManager content = Game.Content;
            spriteBatch = new SpriteBatch(GraphicsDevice);
            menuFont = content.Load<SpriteFont>("menuFont");
            hudFont = content.Load<SpriteFont>("hudFont");
            foreach (GameScreen screen in screens)
            {
                screen.LoadContent();
            }
        }

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

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

            bool otherScreenHasFocus = !Game.IsActive;
            bool coveredByOtherScreen = false;

            while (screensToUpdate.Count > 0)
            {
                GameScreen screen = screensToUpdate[screensToUpdate.Count - 1];
                screensToUpdate.RemoveAt(screensToUpdate.Count - 1);
                screen.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen);
                if (screen.ScreenState == ScreenState.Active)
                {
                    if (!otherScreenHasFocus)
                    {
                        screen.HandleInput(input);
                        otherScreenHasFocus = true;
                    }
                }
            }

            base.Update(gameTime);
        }

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

        public void AddScreen(GameScreen screen)
        {
            screen.ScreenManager = this;
            if (isInitialized)
            {
                screen.LoadContent();
            }
            screens.Add(screen);
            TouchPanel.EnabledGestures = screen.EnabledGestures;
        }

        public void RemoveScreen(GameScreen screen)
        {
            if (isInitialized)
            {
                screen.UnloadContent();
            }

            screens.Remove(screen);
            screensToUpdate.Remove(screen);
        }

        public GameScreen[] GetScreens()
        {
            return screens.ToArray();
        }
    }
}