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Groups > comp.lang.java.gui > #4877

Re: Scope of a JLabel? Also "unchecked operation"

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On 1/3/2012 11:02 AM, A B wrote:

> 2) The itemStateChanged method can't recognise a perfectly good
> JTextArea that I want it to output to, just keeps saying that there is
> no variable called "display".


Right, now that I can read the darn thing, I can see that "display" is a 
local variable, and not accessible outside of the constructor (or before 
it's declared, in fact).

    public Vectorine() {
	...
       JTextArea display = new JTextArea("Type here.", 4, 18);
	...
    }

    public void itemStateChanged(ItemEvent event) {
	...
       display.setText("Option chosen: " + choice);
	...
    }

So the first instance of "display" can't bust out of those braces there 
("{}") because it has local scope.  You need to declare display with a 
broader scope to allow it to be recognized in both methods (probably 
instance scope).  For example:


class Vectorine extends JFrame implements ItemListener {
    private JTextArea display;

    public Vectorine() {
	...
       display = new JTextArea("Type here.", 4, 18);
	...
    }

    public void itemStateChanged(ItemEvent event) {
	...
       display.setText("Option chosen: " + choice);
	...
    }
}

<http://docs.oracle.com/javase/tutorial/java/javaOO/variables.html>

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Thread

Scope of a JLabel?  Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-03 19:02 +0000
  Re: Scope of a JLabel?  Also "unchecked operation" markspace <-@.> - 2012-01-03 11:05 -0800
  Re: Scope of a JLabel?  Also "unchecked operation" markspace <-@.> - 2012-01-03 11:18 -0800
    Re: Scope of a JLabel?  Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-03 21:22 +0000
      Re: Scope of a JLabel?  Also "unchecked operation" markspace <-@.> - 2012-01-03 14:10 -0800
        Re: Scope of a JLabel?  Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-04 21:05 +0000
          Re: Scope of a JLabel?  Also "unchecked operation" markspace <-@.> - 2012-01-04 13:10 -0800
          Re: Scope of a JLabel?  Also "unchecked operation" "Gavino" <invalid@invalid.invalid> - 2012-01-05 19:54 +0100
            Re: Scope of a JLabel?  Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-12 18:51 +0000
  Re: Scope of a JLabel? Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-04 20:58 +0000
    Re: Scope of a JLabel? Also "unchecked operation" "A B" <@bleBaker.uk> - 2012-01-12 18:53 +0000

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