Re: [riena-dev] ListenerList vs ArrayList

[Christian Campo <christian.campo@xxxxxxxxxxxx>]

I think we should agree on something (either duplicates or not). Now  
you, Elias, removed the ListenerList to allow duplicates while
Thorsten just on monday replaced an ArrayList with the ListenerList.

There should be a unique policy throughout Riena. I am sure what the  
policy is in Eclipse. I thought the ListenerList that we use is just
a copy of the class of Riena with an API that supports Generics. So  
the "offiicial" class in Eclipse that should be used for Listeners  
does not
allow duplicates (or better it ignores them).

If you ignore what could happen is that if you add the same listener  
twice and then remove one, no listener is registered (since there is  
no counter). So
can a programmer know that a listener he wants to register (this  
particular instance) is already registered ? If he can, then he is  
doing something wrong
registering it the second time. Its a little that we dont throw an  
exception for duplicates then, but that is the way the Eclipse class  
behaves.

IMHO I think since the ListenerList exists we should use it for each  
and every case where a Listener is required. Since the original  
implementation from
Eclipse ignores duplicates (and hence does not allow them), we could  
think about throwing some kind of runtime exception and document that  
duplicate
listeners are not allowed.

What do you guys think ?

christian


Am 27.08.2008 um 07:31 schrieb Stefan Liebig:

> We could also extend ListenerList to allow duplicates. There is  
> already an enum Mode that could be
> extended for that.
> However, does it make sense for a listener to be notified multiple  
> times for the same event?
>
> Stefan
>
> Volanakis, Elias wrote:
> > Just FYI, in the Tree/Table/List-Ridget I changed the container for  
> > the
> > double click listeners to ArrayList (recently changed to  
> > ListenerList).
> > The reason for using an ArrayList is that adding duplicate  
> > listeners is
> > explicitly permitted there.
> >
> > This fixes the recent test failures in #testAddDoubleClickListener.
> > Feel free to discuss if you disagree. The alternative is to adjust  
> > the
> > tests / javadoc to disallow duplicate listeners.
> >
> > Thanks,
> > Elias.
> >
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