Quick dumb question

Programming Questions

innocentb..

in Programming Questions • 2 years ago

Okay I feel a little guilty for asking this question but...

I'm starting a new project with a class called Background, and the method updateBG in the Background class works when it is called from setup() but not draw() (it gives me a null pointer exception).

Here's the full code of my project so far...

int x;
Background bg;
void setup(){
size(800,400);
Background bg = new Background(0,40,60);
updateBG(); //this works
}
void draw(){
print("test");
bg.updateBG(); //this doesn't
}
class Background {
Background(int r, int g, int b){
background(r,g,b);
}
public void updateBG(){
background(255);
}
}

Replies(2)

quarks

In line 2 you declare a global variable called bg which being being global is available to the whole sketch.

In line 6 you declare a second bg, which since it is declared in setup is only vailable in setup, this is called a local vraiable and local variables are not avaiable outside the block {} they are declared in.

Change line 6 to

bg = new Background(0,40,60);

also line 7 needs to be

bg.updateBG();

innocentb..

Re: Quick dumb question

2 years ago

Works great. Thank you so much.

Top Reply