Re: JFrame disaperes after creation.

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 15 May 2009 21:12:37 -0400

Message-ID:

<4a0e1307$0$90262$14726298@news.sunsite.dk>

iMohed@live.se wrote:

Hello guys. what am I doing wrong here ?? Im trying to create a
JFrame from a controler class with

View v = new view(this);

    MFrame[] frames = new MFrame[2];

        for (MFrame mF : frames) {

            mF = new MFrame();
            mF.setLayout(new BoxLayout(mF, BoxLayout.PAGE_AXIS));
            mF.add(mF.name);
            mF.add(mF.msg);
            mF.buttons.setLayout(new BoxLayout(mF.buttons,
BoxLayout.LINE_AXIS));
            int i = 0;
            for (JButton jB : mF.sSP) {
                jB = new JButton(type[i]);

                // ImageIcon iI = new ImageIcon();
                //jB.setIcon(iI);
                mF.buttons.add(jB);
                jB.addActionListener(ssp);
                jB.setActionCommand(type[i]);
                i++;
            }
            mF.add(mF.buttons);
            mF.add(mF.status);
            mF.add(mF.score);
            add(mF);
        }

then when i try to call

v.frames[0].msg.setText("Hello");

I get a nullpointerexception. Now why is that. I just dont get it.

Try run this for a hint:

public class ForLoops {
     public static void main(String[] args) {
         String[] sa = new String[2];
         try {
             for(String s : sa) {
                 s = new String("ABC");
             }
             String s2 = sa[0].substring(0, 1);
             System.out.println("No exception");
         } catch(NullPointerException npe) {
             System.out.println("Exception");
         }
         try {
             for(int i = 0; i < sa.length; i++) {
                 sa[i] = new String("ABC");
             }
             String s2 = sa[0].substring(0, 1);
             System.out.println("No exception");
         } catch(NullPointerException npe) {
             System.out.println("Exception");
         }
     }
}

Arne