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The code in the main method instantiates an object of the GUI class. The code showing in the GUI class definition declares several instance variables, initializing some of them.

Beginning of the constructor for the GUI class

Listing 2 shows the beginning of the constructor for the GUI class.

Listing 2 . Beginning of the constructor for the GUI class.
GUI(){//constructor //Set JFrame size, title, and close operation.setSize(hSize,vSize); setTitle("Copyright 2008,R.G.Baldwin");setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//Create a new drawing canvas and add it to the // center of the JFrame.myCanvas = new MyCanvas(); this.getContentPane().add(myCanvas);//This object must be visible before you can get an// off-screen image. It must also be visible before // you can compute the size of the canvas.setVisible(true); osiWidth = myCanvas.getWidth()/2;osiHeight = myCanvas.getHeight();

The code in Listing 2 is straightforward and shouldn't require an explanation beyond the embedded comments.

Create two off-screen images

Here is where things begin to get interesting. Listing 3 creates two off-screen images and gets a graphics context on each of them.

Listing 3 . Create two off-screen images.
osiA = createImage(osiWidth,osiHeight); Graphics2D g2Da = (Graphics2D)(osiA.getGraphics());osiB = createImage(osiWidth,osiHeight);Graphics2D g2Db = (Graphics2D)(osiB.getGraphics());

Java programs are not constrained to simply draw on the screen. It is possible to create an off-screen image, get a graphics context on it,and use methods of the Graphics and/or Graphics2D classes to draw on the off-screen image.

The off-screen image can then be used for a variety of purposes including:

  • writing the image into a disk file.
  • copying the image to a Canvas object for display on the screen.

Will copy off-screen images to the screen

In this program, we will copy each of the off-screen images to a Canvas object in a side-by-side format (see Figure 1 ) and display the Canvas object on the content pane in a JFrame object.

While animation is not the purpose of using off-screen images in this program, such off-screen images are often used to produce clean animation. Code isexecuted to produce an off-screen image and then the entire image is copied to the screen in a single blast. This prevents the user from seeing thedevelopment of the image that might otherwise be visible if the code was executed to produce the image directly onto the screen.

The createImage method

There are seven different versions of the createImage method in the JDK 1.7 standard library. The version of the method used in this programis defined in the Component class and inherited into the JFrame class. According to the Sun documentation, this method creates anoff-screen drawable image to be used for double buffering.

The two required parameters are width and height. If the image is later displayed on the screen, the units of width and height are measured in pixels.The values contained in the width and height parameters in Listing 3 were computed in Listing 2 . The width of each off-screen image is set to half the width of the canvas. The height of each off-screen image is set to theheight of the canvas. This facilitates the display of the two images in the side-by-side format shown in Figure 1 .

Questions & Answers

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
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.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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