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The overridden LoadContent method is shown in Listing 3 .
Listing 3 . The overridden LoadContent method.
protected override void LoadContent() {
//Create a new SpriteBatch object, which can be// used to draw textures.
spriteBatch = new SpriteBatch(GraphicsDevice);//Load the image
myTexture = Content.Load<Texture2D>("dogcropped");
//Initialize instance variablesspriteCol = 0;
spriteRow = 0;frameWidth = myTexture.Width / spriteColLim;
frameHeight = myTexture.Height / spriteRowLim;msPerFrame = fast;
spriteEffect = flipEffect;winWidth = Window.ClientBounds.Width;
}//end LoadContent The code to load the image, which is a sprite sheet, is the same as code that I have explained in earlier modules.
Some of the instance variables in Listing 1 were initialized when they were declared. Others couldn't be initialized when they were declared for a varietyof reasons.
Some could have been initialized in the constructor and others couldn't because the required information wasn't yet available.
I elected to initialize variables in the LoadContent method. By the time the LoadContent method executes, all of the information necessary to initialize the variables is available.
The variables named spriteCol and spriteRow will be used as counters to keep track of and to specify the column and row fora particular sprite image as shown in Figure 1 . The columns are numbered from 0 through 4 (five columns) and the rows are numbered from 0 through 1 (two rows).
These two variables specify the width and the height of an individual sprite image (see Figure 1 ). The width and the height of the individual sprite images are computed by dividing the total width of the image loaded in Listing 3 by the number of sprite images in a row and by dividing the total height of the imageloaded in Listing 3 by the number of sprite images in a column.
Listing 1 declares two variables named fast and slow and initializes their values to 175 milliseconds and 525 millisecondsrespectively. These two values are used to switch the animation frame rate between a fast rate and a slow rate by assigning one or the other value to thevariable named msPerFrame . The fast value is assigned to msPerFrame in Listing 3 to specify a fast frame rate when the animation begins.
The SpriteEffects enumeration lists the following effectsthat can be applied to a sprite when it is drawn:
The images in the raw sprite sheet shown in Figure 1 are all facing to the left. The FlipHorizontally enumeration value will be used to cause the images to face to the right when the dog is moving from left to rightacross the game window. The None enumeration value will be used to cause the images to face to the left (the default) when the dog is movingfrom right to left across the game window.
This is accomplished with the variables named spriteEffect , flipEffect , and noEffect . The value of spriteEffect is initialized to flipEffect in Listing 3 because the dog starts off moving from left to right.
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