Object help new user

Processing Libraries
1

I’m a realtively new user. I’ve been watching Dan SHiffman videos and studying the examples given in the processing environment. Lately, I’ve been studying the example in the contributed libraries/controlP5/controllers/controlP5Button. In this example there is a function
<
public void controlEvent(ControlEvent theEvent) {
println(theEvent.getController().getName());
n = 0;
}

The argument seems to be an Object(?). But I can not find it in the code. After nosing around a little it seems it is part of the controlP5 library and it is a Java Object. Is this correct? How can I better understand what the function shown above works? Thanks Mike
/>

please format code with </> button * homework policy * asking questions

2

please read the docu of controlP5

the function above is called automatically when a button is clicked for example and allows you to evaluate the button or whatever.

see https://github.com/sojamo/controlp5/blob/master/examples/controllers/ControlP5button/ControlP5button.pde

3

WHere do I find the document controlP5? This is exactly what I’m looking for. I would like to have the opportunity to read about things, rather than guess. Mike

4

I found a document on GitHub. Is this the document you are refering to? I intend to study this and hopefully it will help me out, thanks, Mike

5

I have to admit the documentation is not very good.

see http://www.sojamo.de/libraries/controlP5/#resources

There are also examples directly in the processing IDE:

  • Menu File | Examples | Contributed Libraries | ControlP5

Chrisir

6

Thanks for the reply. Holy Cow there is a large gap between the beginner YouTube videos and these examples. This is where I’m having trouble finding information regarding these items that are beyond the beginner stuff. I started to look over the cp5 radio button example. There is a lot of short cut items here that I can guess at, but what really has me stumped right now is the object method with two dot syntax.
for example;
<theEvent.getGroup().getValue()/>
I don’t want to ask questions for every item like this a comes up. I would like to see a good reference book with how this stuff works. Thanks Mike

7

Well I’m trying to understand how this code works, by guessing. Looking at the control P5 radiobutton example. It has some code;
< cp5 = new ControlP5(this);
r1 = cp5.addRadioButton(“radioButton”)
.setPosition(100,180)
.setSize(40,20)
.setColorForeground(color(120))
.setColorActive(color(255))
.setColorLabel(color(255))
.setItemsPerRow(5)
.setSpacingColumn(50)
.addItem(“50”,1)
.addItem(“100”,2)
.addItem(“150”,3)
.addItem(“200”,4)
.addItem(“250”,5)
;
/>
First what is “this” key word really do? Could I replace it with r1 in this simply example?
Then the rest seems to be a run on statement. There are no ; after each line and just one ; at the end. Is this some kind of short hand? How would you write it out in a long more visual descriptive way? I tried adding ;'s and cp5 prior to the dot’s and r1 = cp5 prior to the dot, but errors occur. Confused, Mike

8

here, the event is the radio button.
It consists of 5 items (the group).

so this: theEvent.getGroup() gives you the object group.

Then we get the value from the group (pressed item)

so this can be written in a row (theEvent.getGroup().getValue()), or you can tear it apart:

    println("\t "+theEvent.getValue());
    ControlGroup gr=theEvent.getGroup();   // step 1 
    myColorBackground = color(int(gr.getValue()*50), 0, 0);     // step 2

Yeah, did you check the JavaDoc?

http://www.sojamo.de/libraries/controlP5/reference/index.html

It’s a reference to your Sketch and hands a pointer to the Sketch. It’s a technical thing, dunno.

No.

Yes.

Yes.

all with the dot are referring to cp5.addRadioButton(“radioButton”)…

so a long form is to use r, the object we are referring to.


  // *********************************
  r = cp5.addRadioButton("radioButton");
  // *********************************

  r.setPosition(20, 160);
  r.setSize(40, 20);
  r.setColorForeground(color(120));
  r.setColorActive(color(255));
  r.setColorLabel(color(255));
  r.setItemsPerRow(5);
  r.setSpacingColumn(50);
  r.addItem("50", 1);
  r.addItem("100", 2);
  r.addItem("150", 3);
  r.addItem("200", 4);
  r.addItem("250", 5);

So when we init the radio button, we pass a lot of values / properties to it.

Chrisir

9

Thanks for the reply, I really appreciate your help. I’ve been reading about ‘this’. Apparently, it passes the current object, which I thought was r1 in the example, to the constructor of the class.Just to be clear, is the controlP5 the class and the .addRadioButton(), for example are functions within that class?
I tried the long notation and found that it still works. I think that I will use the long hand until I really understand what I’m doing.
The last question is in regard to the double dot stuff, for example,
<theEvent.getGroup().getValue()/>
Does this mean that within the function ‘theEvent’ there is another function ‘getGroup()’ and in that function another function getValue()?
Again I appreciate your help. Mike

10
  • A correction: theEvent isn’t a function but a function (aka method in Java) parameter.
  • A parameter is initialized by the argument passed to it when invoking its function.
  • That parameter theEvent is declared as datatype ControlEvent.
  • It means we can access any public member of that type using the operator . dot.
  • Inside that controlEvent() callback function we can see the method getGroup() is invoked over its parameter theEvent.
  • And after that another method named getName() is chain-invoked over the object returned by the method getGroup().
  • In order to know which datatype belongs the object returned by method getGroup() we need to read the docs about datatype ControlEvent though.
11

Thanks, I think I need some time to digest all this, but good stuff. Mike

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