<< Chapter < Page
  Digital signal processing - dsp     Page 18 / 25
Chapter >> Page >

The code in Listing 24 :

  • Creates the JPanel object, and sets its layout property to GridLayout.
  • Creates the requisite number of objects of the MyCanvas class (which extends Canvas), setting the background colors of the panels alternately towhite and gray.
  • Adds the MyCanvas objects to the cells in the grid. (Note that the constructor for each MyCanvas object receives an integer that specifies itsposition in the stack of MyCanvas objects. We will see how that information is used later.)

More routine construction code

The code in Listing 25 is simply more routine code required to:

  • Finish the construction of the GUI object
  • Set its location and size on the screen
  • Make it visible

Once again, I will let the comments serve as the explanation for this code.

Listing 25. More routine construction code.
//Add the sub-assemblies to the // frame. Set its location, size,// and title, and make it visible. getContentPane().add(ctlPnl,"South"); getContentPane().add(canvasPanel,"Center"); setBounds(0,0,frmWidth,frmHeight);setTitle("Graph01, " + "Copyright 2002, " +"Richard G. Baldwin"); setVisible(true);//Set to exit on X-button click setDefaultCloseOperation(EXIT_ON_CLOSE); //Get and save the size of the// plotting surface width = canvases[0].getWidth(); height = canvases[0].getHeight();

Force a repaint

As you will see later, the actual plotting behavior of this program is defined by the code in an overridden version of the paint method in the MyCanvas class. I will discuss that code in some detail later.

One way to cause the code in the overridden paint method to be executed is to call the repaint method on a reference to a MyCanvas object.

The code in Listing 26 calls the repaint method on each MyCanvas object in sequence, to guarantee that they are properly painted when the GUI object first becomes visible.

Listing 26. Force a repaint.
for(int cnt = 0; cnt<number; cnt++){ canvases[cnt].repaint(); }//end for loop}//end constructor

Similar code will be used again later to cause the graphs to be repainted each time the user presses the Graph button in the bottom right corner of Figure 1 .

End of the constructor

The code in Listing 26 also ends the constructor for the GUI object. When the constructor finishes execution, the GUI appears on the screen with all plotting areas properly painted.

Re-plotting the data

[link] shows the beginning of the event handler that is registered on the button to cause the functions to be re-plotted.

Beginning of the re-plot code.
public void actionPerformed( ActionEvent evt){//Re-instantiate the object that // provides the datatry{ if(args != null){data = (GraphIntfc01)Class. forName(args).newInstance();}else{ data = new junk();}//end else }catch(Exception e){//Known to be safe at this point. // Otherwise would have aborted// earlier. }//end catch

The purpose of the event handler is to cause the functions to be re-plotted after the user changes the plotting parameters.

Questions & Answers

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
QuizOver.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Digital signal processing - dsp' conversation and receive update notifications?