how to load an image inside an extended class?

Contributed Library Questions

davos111

how to load an image inside an extended class?

in Contributed Library Questions • 1 year ago

Hi,

Am I missing something to load an image in a extended class?

the next example works when the class "Module" is a normal class, but fails when class "Module" is an extended class:

I got this error in an extended class: Exception in thread "Animation Thread" java.lang.NullPointerException

Am I missing something to initialize?

thank you a lot

import org.gicentre.utils.multisketch. *;

// Path

PImage imagen;

String path = sketchPath;

String dpath =dataPath("");

Module[] mods;

int count=201;

void setup(){

size(640, 360);

println("DP"+dataPath(""));

dpath =dataPath("");

mods = new Module[count];

println("DP"+dpath);

int cont = 0;

for (int y = 1; y <=5; y++) {

for (int x = 1; x <=3; x++) {

cont=cont+1;

mods[cont] = new Module("name"+x+":"+y, "photo.jpg",50*x,60*y);

}}

}

void draw() {

// background(0);

for (int i = 1; i < (15); i++) {

println("i"+i);

mods[i].update();

println("updated");

mods[i].draw();

println("drawed");

ellipse(120,120,40,40);

}

class Module extends EmbeddedSketch{

String nombre;

String archivo;

int xtemp;

int ytemp;

PImage imagen;

//PImage imagen;

Module(String nombre_, String archivo_, int xtemp_, int ytemp_) {

nombre= nombre_;

archivo=archivo_;

xtemp=xtemp_;

ytemp=ytemp_;

}

void setup(){

};

void update() {

String route=dpath+"/"+archivo; //directory path plus file

println("route"+route); // the path to the image

imagen=loadImage(route); //here the route is correct

image(imagen,40,60); //here the errorr null pointer exception appears when it is in an extended class...

}

void draw() {

ellipse(20,20,50,50);

}

Replies(7)

calsign

Re: how to load an image inside an extended class?

1 year ago

Firstly, why are you loading the image every time that update() is called?
Call it once when it is initialized...

Then, are you sure that the image you have loaded isn't null?
You can check with the following:

if(imagen.equals(null)) println("The image is null!");

That would explain the error...

Also, you might have to initialize your path variables inside setup() - there's a chance that they won't work properly beforehand.

davos111

Re: how to load an image inside an extended class?

1 year ago

Hi,

Thank you for your comment about calling the image in update(), I will check it.

I just set dataPath in the setup(), and inside the class in setup().

yes, the image is not null using :

if(imagen.equals(null)) { println("The image is null!");} else {println("not null");}; //it prints 'not null'

but the null pointer exception continues in the image(imagen,40,60) part...

is there another variable that I should setup?

thank you a lot

void setup(){

size(640, 360);

println("DP"+dataPath(""));

dpath =dataPath("");

dataPath("/Users/myusername/Documents/Processing/xx/data/");

mods = new Module[count];

}

class Module extends EmbeddedSketch{

void setup(){

// dataPath(dpath);

dataPath("/Users/myusername/Documents/Processing/xx/data");

println("datapath es>"+dataPath(""));

};

void update() {

imagen=loadImage(route); //here the route is correct

println("datapath is>"+dataPath(""));

if(imagen.equals(null)) { println("The image is null!");} else {println("not null");}; //it prints 'not null'

image(imagen,40,60); //here the errorr null pointer exception appears when it is in an extended class...

println("after");

}

PhiLho

Re: how to load an image inside an extended class?

1 year ago

The dataPath("/Users/myusername/Documents/Processing/xx/data/"); call sets nothing. It is a function to return a path, not to set it. If you have an absolute path, just use it.
What calsign was meaning was to define a global string variable, initialize it in setup(), and use it in your class.

Note that the line String dpath =dataPath(""); you defined at the global level just won't work: such function must be called within setup(), because at global level they are called before setup() is called, and that's only after size() is called that the path is defined. So your problem has nothing to do with the fact you extend a class or something.

Why don't you just do imagen = loadImage(archivo);? Internally, it calls dataPath(), so your convoluted path computing isn't useful, as long as the image file is in the data folder inside the sketch.

You can println() the path you get in the class, to ensure it is correct inside your class.

davos111

Re: how to load an image inside an extended class?

1 year ago

ok. thank you for the explanation about when it sets data path, and your time.

but, yes, the problem has to be with extending a class.

(I added the data path after trying to solve the problem).

at first I tried using:

imagen=loadImage(archivo);

(that is where this problem started because it loads the image when is in a class and it is null when it is in an extended class)

imagen=loadImage(archive);

the proof of this is that a simple imagen=loadImage(archivo) works inside a class and load the image, and it gives the null error if change only the class to extends EmbeddedSketch, or extends NApplet, ...

so, that is when I tried to look for the path, found the dataPath, and printing it path then it said /Applications/null/data, or /null/data. and tried to add it in the loadImage ("path"+file), or in loadImage(variablewithpath) directly ;, and after that I tried the datapath.

so, I guess that the /null in the path is why it can't find the image when it is extend.

I will check for the data path variable in the setup part...

thank you

PhiLho

Re: how to load an image inside an extended class?

1 year ago

Mmm, sketchPath which is the base variable to compute dataPath() is public, so it lets rogue libraries to change it for some obscure reason (perhaps EmbeddedSketch wants to simulate multiple sketches by manipulating this variable, among others). So they bring havoc in sketches relying on these (under-documented) functions.
So your hope is indeed to load the image, or set the path, in setup().

The problem wasn't about "extended class" in general, but extending EmbeddedSketch. So this thread should probably have been put in the Contributed Libraries section, as hinted by your import.

davos111

Re: how to load an image inside an extended class?

1 year ago

thank you,

I was thinking that I was forgetting something in programming when I try to load the image... because it happened in extending Embedded Sketch and extending NApplet.

oki, next time I will look for contributed libraries section

thank you

davos111

Re: how to load an image inside an extended class?

1 year ago

You are right...

I found a page about the EmbeddedSketch, and they say that loadImage directory is changed, and we have to set the parent directory in a variable. it works now...

thank you

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