exception: contentPane cannot be set to null.

[Chaosje]

hey there,

im a programmer thats new to the world of Java and im having an issue :S
I'm trying to create a program, and it gives me the following error:
"
IllegalComponentStateException: contentPane cannot be set to null."

i have no idea how i should be doin this, and dont know if its even possible the way ive programmed this so maybe you guys could give me a hand?

thx in advance....

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;

/**
 *
 * @author Chaos
 */
public class CronusApp extends JFrame implements ActionListener{
   private JMenuBar menubar;
    private JMenu Bestand, Opties;
    private JMenuItem Sluiten, Help;
    private Login loginpaneel;
    private KeuzePanel keuzepaneel;


    public CronusApp()
    {
        //hier even ingelogd bijgezet om te testen, als deze veranderd naar fals, verdwijnt het inlogscherm en komt het keuzepanel tevoorschijn
         boolean ingelogd = false;

      loginpaneel = new Login();
      if (ingelogd == true)
      {
          setContentPane(loginpaneel);

         //dit zijn de 2 menu keuzes
        menubar = new JMenuBar();
        Bestand = new JMenu("Bestand");
        Opties = new JMenu("Opties");
        menubar.add(Bestand);
        menubar.add(Opties);

        //dit zijn de knoppen in het menu
        Sluiten = new JMenuItem("Sluiten");
        Help = new JMenuItem("Help");
        Bestand.add(Sluiten);
        Opties.add(Help);

        Sluiten.addActionListener(this);
        Help.addActionListener(this);

        setJMenuBar(menubar);
      }
      if(ingelogd == false)
      {
          setContentPane(keuzepaneel);
      }
      
       
    }
}

p.s. i havent added the action performed, but they are somewhere down here, theyre just not part of the problem and i wanted to save you useless lines of code

[ojn]

It's guessing it's

setContentPane(keuzepaneel);

that's causing the error. keuzepaneel is never initialized and therefor null.

[Chaosje]

so how should it be ? :$

i thought naming the attribute and then placin the contentpane was enough :S
since "keuzepaneel" is an instance of "KeuzePanel(a different class)".. or am I just understanding it wrong?

if so ,

how should it be ?

[Jodokus]

since "keuzepaneel" is an instance of "KeuzePanel(a different class)".. or am I just understanding it wrong?

Yes. you are. It is just a declaration of a variable of the proper type.
Like ojn remarked you have to initialize it, e.g. by constructing it like:
private KeuzePanel keuzepaneel = new KeuzePanel();
provided this constructor exists. Only after that "keuzepaneel" is referencing an instance.

[Chaosje]

Thank you, that totally clarified it for me :D
you guys r the best :D

[Jodokus]

ojn and I both have reputation 0 until now. :confused:
Mark your thread as solved.