Good point, you win the pool! On Mar 30, 12:43 am, Alexey Zinger <[email protected]> wrote: > My money is jLabel2 is null. Even if userID is null, jLabel2.setText("" + > userID) should still work. Not to mention that calling JLabel.setText with > null is allowed. > > Alexey > 2001 Honda CBR600F4i (CCS) > 2002 Suzuki Bandit 1200S > 1992 Kawasaki > EX500http://azinger.blogspot.comhttp://bsheet.sourceforge.nethttp://wcollage.sourceforge.net > > ________________________________ > From: Casper Bang <[email protected]> > To: The Java Posse <[email protected]> > Sent: Mon, March 29, 2010 6:15:55 PM > Subject: [The Java Posse] Re: Changing JLabel text from other Class > > First of all, there are far better forums for these kind of questions. > A good one would be Sun's Swing > forum:http://forums.sun.com/forum.jspa?forumID=57 > > Secondly, your code is practically impossible to read because of all > the comments. When you post sample code, remember to trim it down to > just the essentials where the problem is reproducible. > > Third, when encountering an NPE (Null Pointer Exception), one of the > referenced objects must not have been instantiated. Start tracing > backwards from there and deduce where Null could've been introduced, > either by logically tracking code paths or by using a debugger. > > The culprit in this case is userID, based on the fact that the > exception is thrown from the event dispatching thread which is invoked > when you call setText. You have an awful lot of similar variables, uID > as the parameter, userIDapp as a copy of uID that you print out and > then finally the userID which you probably never set. > > /Casper > > On Mar 29, 7:34 pm, Marco <[email protected]> wrote: > > > > > Hello, > > > I have 2 classes one is the application and the other one the login > > screen, when i start the application i create a JFrame with the login > > screen. My login screen checks the username and password in a mysql db > > and when correct it returns the userID to the application (because the > > application needs to know this). This al works with the following > > code : > > > in the login screen class 'Login' i have the code > > [code] > > > Agenda ag = new Agenda(); > > > ... > > > if(userOK){ > > System.out.println("userOK gets executed."); //to check if the > > credentials where ok > > jLabel1.setBackground(Color.green); > > jLabel1.setText("You can enter"); //jLabel1 on the login > > screen itself > > System.out.printf("userid %d\n",userID); //to check the value of the > > userID (this works) > > ag.setUserID(userID); //method in the application class > > 'Agenda' to set the userID there > > } > > [/code] > > > in the application class 'Agenda' i have the setUserID method: > > [code] > > public void setUserID(int uID){ > > System.out.println("setUserID"); //to check if the method gets > > called = ok > > userIDapp=uID; > > System.out.printf("userid %d\n",userIDapp);//to check if the uID > > argument gets assigned to the locale variable userIDapp = ok > > jLabel2.setText(""+ userID); //when i try to set the text of > > jLabel2 a JLabel in the 'Agenda' class i get an error also when i just > > put jLabel2.setText("test");} > > > [/code] > > > the error: > > > Exception in thread "AWT-EventQueue-1" java.lang.NullPointerException > > at agenda.Agenda.setUserID(Agenda.java:93) > > > line 93 = > > [code] > > jLabel2.setText(""+ userID); > > [/code] > > > I'm still learning so if i make big mistakes here forgive me and teach > > me better ways > > > thanks > > > Marco > > -- > You received this message because you are subscribed to the Google Groups > "The Java Posse" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group > athttp://groups.google.com/group/javaposse?hl=en.
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