C:/Users/Andreas Schiffler/Desktop/SVN/NewGamePhysics/GravityChooser/Screens/GravityChooserLoadingScreen.cs

//-----------------------------------------------------------------------------
// GravityChooserLoadingScreen.cs
// (A. Schiffler, 2009-2011)
//-----------------------------------------------------------------------------

namespace GravityChooser
{
    using System;
    using Microsoft.Xna.Framework;
    using Microsoft.Xna.Framework.Graphics;
    using NewGamePhysics.StateManager;

    class GravityChooserLoadingScreen : GameScreen
    {
        #region Fields

        bool loadingIsSlow;

        bool otherScreensAreGone;

        GameScreen[] screensToLoad;

        #endregion

        #region Initialization

        private GravityChooserLoadingScreen(ScreenManager screenManager, bool loadingIsSlow,
                              GameScreen[] screensToLoad)
        {
            this.loadingIsSlow = loadingIsSlow;
            this.screensToLoad = screensToLoad;

            TransitionOnTime = TimeSpan.FromSeconds(0.5);
        }

        public static void Load(ScreenManager screenManager, bool loadingIsSlow,
                                PlayerIndex? controllingPlayer,
                                params GameScreen[] screensToLoad)
        {
            // Tell all the current screens to transition off.
            foreach (GameScreen screen in screenManager.GetScreens())
                screen.ExitScreen();

            // Create and activate the loading screen.
            GravityChooserLoadingScreen loadingScreen = new GravityChooserLoadingScreen(screenManager,
                                                            loadingIsSlow,
                                                            screensToLoad);

            screenManager.AddScreen(loadingScreen, null);
        }

        #endregion

        #region Update and Draw

        public override void Update(GameTime gameTime, bool otherScreenHasFocus,
                                                       bool coveredByOtherScreen)
        {
            base.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen);

            // If all the previous screens have finished transitioning
            // off, it is time to actually perform the load.
            if (otherScreensAreGone)
            {
                ScreenManager.RemoveScreen(this);

                foreach (GameScreen screen in screensToLoad)
                {
                    if (screen != null)
                    {
                        ScreenManager.AddScreen(screen, null);
                    }
                }

                // Once the load has finished, we use ResetElapsedTime to tell
                // the  game timing mechanism that we have just finished a very
                // long frame, and that it should not try to catch up.
                ScreenManager.Game.ResetElapsedTime();
            }
        }

        public override void Draw(GameTime gameTime)
        {
            // If we are the only active screen, that means all the previous screens
            // must have finished transitioning off. We check for this in the Draw
            // method, rather than in Update, because it isn't enough just for the
            // screens to be gone: in order for the transition to look good we must
            // have actually drawn a frame without them before we perform the load.
            if ((ScreenState == ScreenState.Active) &&
                (ScreenManager.GetScreens().Length == 1))
            {
                otherScreensAreGone = true;
            }

            // The gameplay screen takes a while to load, so we display a loading
            // message while that is going on, but the menus load very quickly, and
            // it would look silly if we flashed this up for just a fraction of a
            // second while returning from the game to the menus. This parameter
            // tells us how long the loading is going to take, so we know whether
            // to bother drawing the message.
            if (loadingIsSlow)
            {
                SpriteBatch spriteBatch = ScreenManager.SpriteBatch;
                SpriteFont font = ScreenManager.Fonts["game"];

                const string message = "Loading...";

                // Center the text in the viewport.
                Viewport viewport = ScreenManager.GraphicsDevice.Viewport;
                Vector2 viewportSize = new Vector2(viewport.Width, viewport.Height);
                Vector2 textSize = font.MeasureString(message);
                Vector2 textPosition = (viewportSize - textSize) / 2;

                Color color = new Color(255, 255, 255, TransitionAlpha);

                // Draw the text.
                spriteBatch.Begin();
                spriteBatch.DrawString(font, message, textPosition, color);
                spriteBatch.End();
            }
        }

        #endregion
    }
}

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