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Then Listing 9 calls the drawString method on the graphics context received as an incoming parameter of type Graphics to display the value in the first line of text near the center of Figure 1 .

The drawString method takes three parameters. The first is the string that is to be drawn in the game window and the next two are the horizontal and verticalcoordinates for the location in which the string is to be drawn.

Draw the saved value of delta

Then Listing 9 calls the drawString method again to draw the saved value of delta from the most recent call to the update method as the second line of text near the center of Figure 1 .

End of discussion

That concludes the discussion of the program named Slick0130a . Although this is a simple program, it should provide a little more insight intoone approach to creating a game program using the Slick2D library.

Run the program

I encourage you to copy the code from Listing 10 . Compile the code and execute it,making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.


You learned about a property of the GameContainer class named running , and how it is used by the start method to keep the game loop running.

You learned about the salient features of the gameLoop method of the AppGameContainer class.

You learned about the updateAndRender method of the GameContainer class and how it decides when and if to call the update and render methods of the object of the Game class that is wrapped by the container.

You touched on the difference between normal delta and smoothed delta.

You learned about minimumLogicInterval and maximumLogicInterval and how the contents of those two variables are used to determine if, when, and how many times to call the update method during each iteration of the game loop. You also learned how the contents of these twovariables are used to determine the value that is passed as delta each time the update method is called.

You learned that the render method is normally called once and only once during each iteration of the game loop.

You saw a simple example of how you can use the value of delta that is received by the update method to control the behavior of a game program.

You learned that you can set the size of the game window when you instantiate an object of the AppGameContainer class by passing dimension parameters to the constructor.

You learned that you can set the target frame rate by calling the setTargetFrameRate method on the GameContainer object.

You learned how to display text in the game window.

What's next?

In the next module, we will take a look at displaying images with transparency.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Slick0130: The game loop
  • File: Slick0130.htm
  • Published: 02/04/13
  • Revised: 06/09/15 for 64-bit

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

Complete program listing

Listing 10 provides a complete listing of the program named Slick0130a .

Listing 10 . Source code for the program named Slick0130a.
/*Slick0130a.java Copyright 2012, R.G.BaldwinA very skinny Slick program. Barely more than a skeleton. Tested using JDK 1.7 under WinXP*********************************************************/ import org.newdawn.slick.AppGameContainer;import org.newdawn.slick.BasicGame; import org.newdawn.slick.GameContainer;import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException;public class Slick0130a extends BasicGame{//Instance variables for use in computing and // displaying total time since program start and// time for each frame. double totalTime = 0;int incrementalTime = 0; public Slick0130a(){//Call to superclass constructor is required. super("Slick0130a, Baldwin.");}//end constructor //----------------------------------------------------//public static void main(String[] args)throws SlickException{ try{AppGameContainer app = ( new AppGameContainer(new Slick0130a(),400,200,false)); app.start();}catch(SlickException e){ e.printStackTrace();}//end catch }//end main//----------------------------------------------------// @Overridepublic void init(GameContainer gc) throws SlickException {//Set the frame rate in frames per second. gc.setTargetFrameRate(2);}//end init//----------------------------------------------------// @Overridepublic void update(GameContainer gc, int delta) throws SlickException{//Compute and save total time since start in seconds. totalTime += delta/1000.0;//Save delta for display in render method.incrementalTime = delta;}//end update //----------------------------------------------------//public void render(GameContainer gc, Graphics g) throws SlickException{//Truncate totalTime to one decimal digit and // displaydouble time = (int)(totalTime*10)/10.0; g.drawString("totalTime: "+time,100.0f,100.0f);//Display incremental time.g.drawString("incrementalTime: " + incrementalTime, 100.0f,120.0f);}//end render }//end class Slick0130a


Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
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
How can I make nanorobot?
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
how can I make nanorobot?
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Anatomy of a game engine. OpenStax CNX. Feb 07, 2013 Download for free at https://legacy.cnx.org/content/col11489/1.13
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