A general GameScreen implementation

A few weeks ago, Eli posted a design for a GameScreen and a GameScreenManager to use in XNA. The GameScreen is a base class, like Game, that implements one layer of a game (e.g. the game itself, or a menu, or a title screen). The GameScreenManager is used by the Game class to switch between these screens using a stack-based design.

I ended up implementing this design for my book, and I've been using a few weeks with no problems so I thought I'd post it here for the XNA community to use. To use the GameScreenManager, declare a public instance of it on your Game object, along with any screens that are spawned by Game and not by other screens.


public GameScreenManager screenManager;
// Screens
StartMenuScreen menuscreen;
PlayScreen play;


public Game1()
{

...
screenManager = new GameScreenManager(2);
...

}

Add the first screen during Game.Initialize() by creating the screen, initializing it, and calling GameScreenManager.Push. I also create the other screen at this point, but I don't initialize it until it's invoked.


protected override void Initialize()
{

// TODO: Add your initialization logic here
play =
new PlayScreen(this);
play.Initialize();
screenManager.Push(play);
menuscreen = new StartMenuScreen(this);
...

}

At some point later, if the menu is invoked, I initialize it and push it over top of the play screen:

// if the menu isn't already up
if (screenManager.Peek() != menuscreen)
{
GamePad.SetVibration(PlayerIndex.One, 0, 0);
// install menu screen
menuscreen.Initialize();
screenManager.Push(menuscreen);


Lastly, when the menu is finished, I fire an event back Game, which removes it.

public void MenuScreenFinished(int Selection)
{

screenManager.Pop();
if (Selection == 0)
return;
if (Selection == 1)
{
play.ResetGame();
}
if (Selection == 2)
{
this.Exit();
}

}

You can download the GameScreen.cs and a sample screen here.

Also, I should probably hawk the fact that my book is available for pre-order.