<< Chapter < Page
  Xna game studio     Page 2 / 11
Chapter >> Page >

General background information

You learned how to design, create, and use a simple Sprite class in an earlier module. You also learned to use a generic List object to store references to objects of the Sprite class.

Preview

I will explain improvements made to the Sprite class and will show you how to write a Game1 class that takes advantage of those improvements.

The screen output

Figure 1 shows a reduced screen shot of the program while it is running.

Figure 1 . Screen shot of the running program.

missing image

Lots and lots of sprites

When this screen shot was taken, the program had 24 space rocks, 12 red power pills and six UFOs all navigating in the game window.

Discussion and sample code

As usual, I will discuss and explain the program code in fragments. A complete listing of the Sprite class is provided in Listing 19 and a complete listing of the Game1 class is provided in Listing 20 .

The Sprite class

The Sprite class begins in Listing 1 with the declaration of several instance variables.

Listing 1 . Beginning of the Sprite class.

namespace XNA0128Proj { class Sprite {private Texture2D image; private Vector2 position = new Vector2(0,0);private Vector2 direction = new Vector2(0,0); private Point windowSize;private Random random; double elapsedTime;//in milliseconds//The following value is the inverse of speed in // moves/msec expressed in msec/move.double elapsedTimeTarget;

The purpose of these instance variables will become clear later in the discussion.

Properties

This class has the following properties:

  • Position - position of the sprite in the game window relative to the upper left corner of the game window. The X and Y values aresaved as type Vector2 in the instance variable named position .
  • WindowSize - The dimensions of the game window. The width and height values are saved as type Point in the instance variable named windowSize .
  • Direction - Direction of motion of the sprite expressed as a 2D vector with an X and a Y component. The length of this vector is thedistance that the sprite moves each time it moves. The values are saved as type Vector2 in the instance variable named direction .
  • Speed - Speed of the sprite expressed in moves per millisecond. The actual speed in pixels per millisecond is the product ofthis value and the length of the direction vector.

Other instance variables

In addition, the class has the following instance variables that are set either by the constructor or by a method:

  • image - the image that is drawn to represent the sprite in the game window. The image can be modified as the game progresses throughcalls to the SetImage method.
  • random - a reference to a random number generator.
  • elapsedTime - used to keep track of the amount of elapsed time in milliseconds since the last time that the sprite wasactually moved.
  • elapsedTimeTarget - will be explained later.

The first three property accessor methods

The first three property accessor methods are shown in Listing 2 .

Listing 2 . The first three property accessor methods.

//Position property accessor public Vector2 Position {get { return position;} set {position = value; }//end set}//end Position property accessor //-------------------------------------------------////WindowSize property accessor public Point WindowSize {set { windowSize = value;}//end set }//end WindowSize property accessor//-------------------------------------------------// //Direction property accessorpublic Vector2 Direction { get {return direction; }set { direction = value;}//end set }//end Direction property accessor

Questions & Answers

what is biology
Hajah Reply
the study of living organisms and their interactions with one another and their environments
AI-Robot
what is biology
Victoria Reply
HOW CAN MAN ORGAN FUNCTION
Alfred Reply
the diagram of the digestive system
Assiatu Reply
allimentary cannel
Ogenrwot
How does twins formed
William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
what is genetics
Josephine Reply
Genetics is the study of heredity
Misack
how does twins formed?
Misack
What is manual
Hassan Reply
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
Joseph Reply
what is biology
Yousuf Reply
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
Joseph Reply
what is the blood cells
Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
What is classification
ISCONT Reply
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Condoleezza Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Xna game studio' conversation and receive update notifications?

Ask