Creating a Simple XNA Windows Phone 7 Application

1. Problem

You have to create a Windows Phone 7 application by using XNA.

2. Solution

Use Visual Studio 2010 (either Express, Professional, or Superior edition). Use the Windows Phone Game (4.0) project template.

3. How It Works

Press Ctrl+Shift+N after opening Visual Studio 2010. This brings up the New Project dialog box. Select the XNA Game Studio 4.0 template from the Installed Templates on the left and select the Windows Phone Game (4.0) project template (see Figure 1). Type SimpleXNAApplication in the project Name text box and then click the OK button.

Figure 1. Create a new XNA Windows Phone 7 application by using the Windows Phone Game (4.0) project template.

After few moments, you will have two projects in the solution. One contains the files to create the game, and the other is specifically for game resources such as sprites, images, and sounds.

3.1. The Code

The main file in the project is Game1.cs; it contains the code to create a game in Windows Phone 7 using the Game1 class derived from the Game class (in Figure 2 is shown its own class diagram). The project template does nothing relevant other than creating the code to paint the screen with the CornflowerBlue color. But it is worth noting the class structure and its methods to understand how the XNA game works.

Figure 2. The Game1 and Game classes diagram.

In the class's constructor, a GraphicsDeviceManager object is created. This object represents the graphic device manager of the Windows Phone and contains properties used to change resolution, toggle full-screen mode, and more. It sets the refreshing frame rate to 30 frames per second (fps), which means that in 1 second, the Update method is called 30 times.

public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";

            // Frame rate is 30 fps by default for Windows Phone.
            TargetElapsedTime = TimeSpan.FromTicks(333333);
        }

The Initialize method is where you have to put the code to initialize your objects.

protected override void Initialize()
        {
            // TODO: Add your initialization logic here

            base.Initialize();
        }

The next method that is called by the XNA framework is LoadContent. In this method, you have to load the content previously added to the Content project in the solution. You can add images, sounds, sprites, 3D models, and all your game resources.

protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            // TODO: use this.Content to load your game content here
        }

					  

Finally, the XNA game framework enters into a loop in which two methods are automatically called one by one—first the Update method and then the Draw method. In the Update method, you have to add the code that manages the game's logic, the sprites' movement, a collision algorithm, and so on. The Draw method is where you draw the game objects and you have to be faster to do it. Your game code shouldn't update and check objects in the Draw method.

protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

					  

// TODO: Add your update logic here

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            // TODO: Add your drawing code here

            base.Draw(gameTime);
        }

There is another method defined in the code that is used to unload the content when the game is closed.

protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

4. Usage

Press Ctrl+F5 to see the game running in the emulator (see Figure 3).

Figure 3. SimpleXNAApplication running on the Windows Phone 7 Emulator