File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
http://aspose.com/file-tools
The moose likes Beginning Java and the fly likes NPE with JTextArea Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Java » Beginning Java
Bookmark "NPE with JTextArea" Watch "NPE with JTextArea" New topic
Author

NPE with JTextArea

scott beveridge
Greenhorn

Joined: Mar 03, 2005
Posts: 11
Hi,

I get an NullPointerException when I try and call a append() or setText() method for a JTextArea but not a JTextField when everything else remains the same. Here is the revelant code.



Then from another class file.


As I said setting the JTextField works fine, but I get an NPE pointing at both references to the JTextArea, please someone tell me what I've done wrong. I'm using JCreator and XP.

Thanks,

Scott

[ June 11, 2005: Message edited by: scott beveridge ]
[ June 11, 2005: Message edited by: scott beveridge ]
KR Campbell
Ranch Hand

Joined: Mar 26, 2004
Posts: 124
Your problem is that you have two variables with the same name but different scope. You have instantiated the local version in createUserInterface() but not the instance variable. Thus, the local one hides the other one. Try:

instead of:

Regards
Kenny
KR Campbell
Ranch Hand

Joined: Mar 26, 2004
Posts: 124
... that is, it hides it within the scope of the method.
scott beveridge
Greenhorn

Joined: Mar 03, 2005
Posts: 11
Thanks for the reply. This still does not work.

I originally had this but changed it because:
When I try this now I get a compile error of

"cannot resolve symbol:
auditJTextArea = new JTextArea();"

and of course everywhere that references it.

I've retyped "new JTextArea()" a thousand times but still no joy.

Scott
Ernest Friedman-Hill
author and iconoclast
Marshal

Joined: Jul 08, 2003
Posts: 24187
    
  34

I don't know about "can't resolve symbol" errors, but you ought to get an "invalid type" error, because auditJTextArea is declared as a TextArea, but you're assigning a JTextArea to it -- those are two different classes.


[Jess in Action][AskingGoodQuestions]
Abdulla Mamuwala
Ranch Hand

Joined: Jan 09, 2004
Posts: 225
Looking back at what Earnest said,



Here auditJTextArea has a reference type TextArea.



and here the runtime object for auditJTextArea is of type auditJTextArea.

Both TextArea and auditJTextArea belong to different class hierarchies, this gives a "Type Mismatch" compile time error.
scott beveridge
Greenhorn

Joined: Mar 03, 2005
Posts: 11
Yeah I've tried both TextArea and JTextArea, usually not at the same time (that doesn't work either).

I think the problem is a mistake in scope somewhere.
I'll keep trying and thanks for your input.

scott
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: NPE with JTextArea