A basic question on accessing one variable from different classes in Eclipse/ JAVA.

fraknoi

A basic question on accessing one variable from different classes in Eclipse/ JAVA.

in Integration and Hardware • 1 year ago

Hi all,

While "migrating" my code from PDE to Eclipse, I came across what I am afraid this is a Java fundamental, but despite my best effrorts, I can't figure it out;

Here is what I am trying to do :

In my main class, I capture a mouse click into a Boolean:

public class MyProcessingSketch extends PApplet ()

public boolean mouseClickedHere ;

…

public void setup () {

mouseClickedHere =true ...

I want to use this boolean in another class:

Public class shapeShow () ;

If (mouseClikedHere) … etc…

Well, that works in PDE (because classes beeing "inner", I suppose?) , but not in Java (I thought that "public" was supposed to do that...).

I know that I could pass the variable as a parameter, but I have tons of those, so it consider it totally unpractical (and ugly). Is there another solution ?

thanks,

Replies(5)

jas0501

Re: A basic question on accessing one variable from different classes in Eclipse/ JAVA.

1 year ago

See

http://processing.org/learning/eclipse/

The global variable in the IDE becomes a variable of the parent PApplet so

PApplet parent;

shapeShow(PApplet p)

{

parent = p;

}

if(mouseClickedHere) ...

would look like

if(parent.mouseClickedHere) ...

fraknoi

Re: A basic question on accessing one variable from different classes in Eclipse/ JAVA.

1 year ago

Thks Jas,

..but I have been trying that as well, and can't get it to work.

So, I just made the test again, based on the example Stripes from the tutorial - in the original version (which works well), the main class passes the mouse coordinates to another class (stripe) as parameters. I altered it to use a variable instead:

In the main class, I created a public variable myMouseX:

... I altered accrodingly the call to the method ...

... and in the stripe class, I used this variable

I get this error, "mYMouseX cannot be resolved or is not a field".

any hint ?

PhiLho

Re: A basic question on accessing one variable from different classes in Eclipse/ JAVA.

1 year ago

You declared parent as PApplet, not as MyProcessingSketch. PApplet has no myMouseX field, indeed.
Two possible cures:
- declare parent as MyProcessingSketch;
or
- access the variable with ((MyProcessingSketch) parent).myMouseX
or
- make a method local variable like MyProcessingSketch mps = (MyProcessingSketch) parent; and use it instead of parent in the method (better if there are several usages).
(Yes, that's more than 2, but the last two are strongly related.)

fraknoi

Re: A basic question on accessing one variable from different classes in Eclipse/ JAVA.

1 year ago

Ahhhh yes! Thanks a lot, phi.lo

So, now I realize that when I pass " this." as the parent class, it is seen either as the subset PApplet , or as the extendesd MyProcessingSketch, depending on how I declared it....Teaches me a (beginer) lesson !

merci encore,

PhiLho

Re: A basic question on accessing one variable from different classes in Eclipse/ JAVA.

1 year ago

Yes, there can be lot of things behind a variable... Your MyProcessingSketch is also a PApplet which is also an Applet and perhaps more, all the way up to begin an Object, like all objects in Java. When going up, you have less methods (and fields) but you make a more generic object: if you set the type to MyProcessingSketch, you have to rename all the cast if you rename the sketch (but Eclipse allows to do it easily) while a PApplet won't change but offers less possibilities.

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