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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 .

Extensibility

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

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.
Bharti
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Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
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Maciej
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for teaching engĺish at school how nano technology help us
Anassong
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
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Devang Reply
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
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Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
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Cied
types of nano material
abeetha Reply
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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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