Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.java.gui > #2051

Re: Listeners Still Respo

Show all headers | View raw

  To: comp.lang.java.gui
Thomas A. Russ wrote:

> Hal Vaughan <hal@thresholddigital.com> writes:
> 
>> I have the following code (with line numbers for convenience):
>> 
>> //jList is a JList
>> 1       jList.setFocusable(false);
>> 2       jList.removeListSelectionListener(this);
>> 3       jList.setListData(new String[0]);       //Clear in case new data
>> is empty //Other code for setting data
>> 11      jList.setSelectedIndex(refIndex);
>> 12      jList.setFocusable(true);
>> 13      jList.addListSelectionListener(this);
>> 14      componentIndex = jList.getSelectedIndex();
>> 
>> I've removed the class itself as the ListSelectionListener at the start
>> (at
>> line 2), then add it later (at line 13).  While testing, I found my data
>> was being updated more frequently than appropriate and when it was
>> updated,
>> it would loop through multiple times.  I tracked it back, by throwing an
>> error and printing a stack trace, to both lines 3 and 11.  Both of these
>> lines, at different times, are triggering the ListSelectionListener.
>>
>> Both of the offending lines are after I've removed the Listener and
>> before I
>> reattach it.  Why are they triggering the Listener when it's not
>> attached?
> 
> My best guess would be that you are adding "this" as a
> ListSelectionListener more than once.  The remove will only remove a
> single instance of the matching listener, not all instances of the
> matching listener.  That would explain both why you still get updates
> after a single removal, as well as why you end up getting multiple
> responses.

That's what it turned out to be.  The problem was one was added within the
class and it was added from the class that created it.  Since they were in
two different places, I didn't make the connection until I took Roedy's
suggestion and had it list the listeners, then realized I had to find where
it was added the 2nd time.

Thanks!

Hal

---
 * Synchronet * The Whitehouse BBS --- whitehouse.hulds.com --- check it out free usenet!
--- Synchronet 3.15a-Win32 NewsLink 1.92
Time Warp of the Future BBS - telnet://time.synchro.net:24

Back to comp.lang.java.gui | Previous | Next | Find similar | Unroll thread

Thread

Re: Listeners Still Respo "Hal Vaughan" <hal.vaughan@THRWHITE.remove-dii-this> - 2011-04-27 15:36 +0000

csiph-web