Processing 1.0 - Processing Discourse - Global Class Costructor or in draw??

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Global Class Costructor or in draw?? (Read 474 times)

G_Rasputin

Global Class Costructor or in draw??
Apr 2^nd, 2007, 12:52pm

Hello Guys,

when i tried to call the class befor the setup or draw command i got a:

java.lang.NullPointerException

at processing.core.PApplet.registerNoArgs(PApplet.java:758)

at processing.core.PApplet.registerDispose(PApplet.java:749)

at de.bezier.mysql.MySQL.<init>(MySQL.java:83)

BUT when i called «MysqlAnfrage Datenbank= new MysqlAnfrage(this);» within draw it workes. But i would like to call it only once.

Does somebody know where my mistake lies?

Thanks a lot!!!

void setup(){

background(0);

size(XSize, YSize);

}

void draw()
{
MysqlAnfrage Datenbank= new MysqlAnfrage(this);

Datenbank.getData(startvon,incIntervall);
......
}

class MysqlAnfrage(){

......

}

st33d

Re: Global Class Costructor or in draw??
Reply #1 - Apr 2^nd, 2007, 1:06pm

Before setup() you should state all the elements you are going to use. You can give primitives values here (int, byte, String, float, etc.) but you can't instantiate objects here.

In setup() you get everything prepared, so here you can instantiate objects and all kinds of stuff.

setup() is rather like a class constructor, you give everything values in it. The bit before the constructor is just for stating the contents - not activating the contents.

fjen

Re: Global Class Costructor or in draw??
Reply #2 - Apr 2^nd, 2007, 1:07pm

ok, aaron was faster ... here's my 2 cents:

Code:


MysqlAnfrage Datenbank;

void setup(){ 
    background(0); 
    size(XSize, YSize); 
    Datenbank= new MysqlAnfrage(this); 
} 
 
void draw() 
{ 
    Datenbank.getData(startvon,incIntervall); 
...... 
} 
 
class MysqlAnfrage(){ 
...... 
}

this is not available before the applet is fully created (except inside it's constructor). calling it outside any global functions will not work correctly. the idea is to use setup() for these kind of things ...

F

G_Rasputin Ex Member	Re: Global Class Costructor or in draw?? Reply #3 - Apr 2^nd, 2007, 1:22pm thanks a lot guys!

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