<< Chapter < Page Chapter >> Page >

Default behavior

As I mentioned above, the default behavior of the sketch is to call the setup method once and to repeatedly call the draw method until the sketch is terminated, regardless of whether or not the setup and draw methods are overridden. If these methods are not overridden, the sketch will produce an output similar to thatshown in Image 1 .


As you will see later, for the sketch shown in Image 2 , the framework has been extended by overriding the setup and draw methods, and by defining a new class named Car . The code for the class named Car is on the hidden tab named Car in Image 2 and is also shown in Listing 1 .

Listing 1. code for the class named car.

class Car { color c;float xpos; float ypos;float xspeed; // The Constructor is defined with arguments.Car(color tempC, float tempXpos,float tempYpos, float tempXspeed) {c = tempC; xpos = tempXpos;ypos = tempYpos; xspeed = tempXspeed;} void display() {stroke(0); fill(c);rectMode(CENTER); rect(xpos,ypos,20,10);} void drive() {xpos = xpos + xspeed; if (xpos>width) { xpos = 0;} }}
Listing 1. Code for the class named Car.

Non-modifiable framework code

While we can extend the Processing framework by overriding methods, defining new methods, defining new classes, etc., we cannot, by default, modify theframework code.

Overall behavior of the Processing framework

Without seeing the source code, it appears that when we click the Run button in Java mode, the Processing framework:

  • Instantiates a new object of a class that we define in the leftmost tab of the PDE.
  • Calls the method named setup , (which may or may not be overridden in the new class) belonging to that object once and only once.
  • Calls the method named draw , (which may or may not be overridden in the new class) belonging to that object repeatedly at a default rate of 60 calls per second until the sketch is terminated.

We can

  • control how often the draw method is executed by calling the frameRate method,
  • prevent the draw method from being executed repeatedly by calling the noLoop method,
  • cause the draw method to be executed repeatedly by calling the loop method
  • cause the draw method to be executed once by calling the redraw method.

Programs or sketches that we write to run under the Processing framework must be compatible with the behavior described above.

Discussion and sample code

Now it's time to put the theory aside and take a look at an actual sketch.

Listing 1 shows the definition of a class named Car . This class is defined on the hidden tab in Image 2 .

Listing 2 shows the definition of the class named Cars in the leftmost tab of Image 2 . I am repeating it here so that you can copy and paste it into your PDE.

Listing 2. code for the class named cars.

Car myCar1;//instance variables Car myCar2;void setup() { size(200,200);myCar1 = new Car(color(255,0,0),0,100,2); myCar2 = new Car(color(0,0,255),0,10,1);}//end setup methodvoid draw() { background(255);myCar1.drive(); myCar1.display();myCar2.drive(); myCar2.display();}//end draw method
Listing 2. Code for the class named Cars.

A subclass of PApplet

You might think of the class that is defined in Listing 2 as the driver class. You will see later that it is a subclass of the Processing class named PApplet .

The name of the new class

When we create a new sketch, this class has a default name something like sketch_130223a .. We can change the name of the class when we select Save or Save As... from the File menu of the PDE.

Saving the sketch causes a sketchbook folder to be created containing a file with a name like sketch_130223a.pde , or whatever name we specify. The name of the sketchbook folder is the same as the nameof the class.

For the case of Image 2 , the sketchbook folder is named Cars and the file is named Cars.pde . (The file named Cars.pde is simply a text file containing Java source code. If you wereworking outside the PDE, you could name it Cars.java.)

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
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
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
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.
While the American heart association suggests that meditation might be used in conjunction with more traditional treatments as a way to manage hypertension
Beverly Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, The processing programming environment. OpenStax CNX. Feb 26, 2013 Download for free at http://cnx.org/content/col11492/1.5
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'The processing programming environment' conversation and receive update notifications?