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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

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
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.
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
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Source:  OpenStax, The processing programming environment. OpenStax CNX. Feb 26, 2013 Download for free at http://cnx.org/content/col11492/1.5
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