XNA Game Studio 4.0 : XNA Game Studio Storage (part 1) - Recreating the Project on Xbox, Devices and Containers

Recreating the Project on Xbox

Because you need to use the storage api, as well as various IO functions, update the using statements at the beginning of your new game1.cs code file:

using System.IO;
using Microsoft.Xna.Framework.Storage;

You need the sprite font again to render the data, so add a new sprite font to your content project named Font. Include the variables for your list of points and the following font:

List<Vector2> points;
SpriteFont font;

Add the initialization of the list in the Initialize overload:

points = new List<Vector2>();

Also, include the creation of the sprite font in your LoadContent overload:

font = Content.Load<SpriteFont>("font");

To render your points, add the following code before the base.Draw call in your Draw overload:

spriteBatch.Begin();
foreach (Vector2 position in points)
{
    spriteBatch.DrawString(font, "x", position, Color.White);
}
spriteBatch.End();

The code that you used to add new points to the screen in the Windows Phone project unfortunately does not work here. There is no touch screen for your Xbox 360! So instead, let users input points with the controller by allowing them to move a cursor around the screen and then pressing the A button to add points. To implement this simple feature, add a couple new variables to your project:

Vector2 currentPos;
GamePadState lastState;

The first variable is the current position of the onscreen cursor, and the second is the last frame’s state of the controller. Initialize the current position variable in your initialization method as well:

currentPos = Vector2.Zero;

To draw the cursor on the screen so users can see where they will place points, add the following line to your project before the End call on spriteBatch:

spriteBatch.DrawString(font, "*", currentPos, Color.Red);

To allow the user to update its position, add the following code to the Update method:

GamePadState state = GamePad.GetState(PlayerIndex.One);
if (state.IsButtonUp(Buttons.A) && (lastState.IsButtonDown(Buttons.A)))
{
    // Add a new point here
    points.Add(currentPos);
}
// Move the current cursor
currentPos.X += (state.ThumbSticks.Left.X * 10);
currentPos.Y -= (state.ThumbSticks.Left.Y * 10);
// Don't let it go beyond the screen
if (currentPos.X < 0)
    currentPos.X = 0;
if (currentPos.Y < 0)
    currentPos.Y = 0;
if (currentPos.X > GraphicsDevice.Viewport.Width)
    currentPos.X = GraphicsDevice.Viewport.Width;
if (currentPos.Y > GraphicsDevice.Viewport.Height)
    currentPos.Y = GraphicsDevice.Viewport.Height;
lastState = state;

The code here is pretty self-explanatory; it adds a new point to the list (at the current position) if the A button was pressed in the last frame and released in this frame. It increments the X member of the current position by how much you press the left thumbstick (multiplying by 10 makes the cursor move faster). It does the same thing with the Y member, except it decrements instead because the Y axis on the stick goes from 1 to –1. It then does some basic bounds to ensure that the cursor stays within the viewport, and stores the last state of the gamepad.

With that portion of the code done, save the data when you exit and restore it when you launch.

Devices and Containers

Let’s take a few moments to discuss the StorageDevice, because it is one of the sources of the most common mistakes when dealing with storage on the Xbox. The Xbox 360 provides a number of places to store data. You might have a hard drive, you might have one or more memory units, and now you can even have USB memory sticks attached. Each one of these is considered a device and can be used to store data for your games. Notice an example of a list of devices in which to choose in Figure 1.

Figure 1. Devices on an Xbox 360

Each device can have a wide variety of containers in it, and much like on the phone, each game has all of its data segregated from all other games. When navigating to the system memory blade in the Xbox 360 dashboard, you can see how much data each game is storing, such as in Figure 2.

Figure 2. Game data on an Xbox 360

StorageContainer objects are the equivalent of the IsolatedStorageFile object you used previously. The big difference is that a game can have multiple containers, where each game is limited to a single isolated storage store. As you can see in Figure 3, this single game has three distinct storage containers in it.

Figure 3. Multiple storage containers per game

When you view this screen on the dashboard, it shows the containers that were created for the game, not the files themselves.