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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.


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.


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

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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