Whether or not the specification of notifying a listener multiple times
was intentional or driven by the implementation, it is part of the spec,
and some applications could be relying on it. I do agree that there is
no guarantee as to the order, which might simplify things. I can think
of two possible implementations:
1. Use a counter as you mentioned below as a possibility. If you did
this, you would need to add an additional LinkedHashSet of objects
containing the Listener and a count. You could initialize that set to
null and only constructing it in the (rather unlikely) case that a
listener is added when it is already in the set of listeners. You could
then test for "if (countSet == null)" in the various operations and do
the simple thing if it is.
2. Since adding a listener more than once is unlikely, you could switch
from a LinkedHashSet to an ArrayList the first time that a listener is
added more than once. You would keep a Collection of listeners,
initialize it to a LinkedHashSet, and dynamically switch from a
LinkedHashSet to an ArrayList (copying existing entries) in addListener
if the collection contains the listener already. This would be simpler
logic than keeping track of the count for each object.
I would lean towards the second optoin. It gives the desired speed up
for the common case where we don't add a listener more than once, and in
the worst case, switches back to what we have today.
-- Kevin
On 2/12/2020 4:03 AM, Danny Gonzalez wrote:
Hi Jeanette,
True, I hadn't read that spec in ObservableValueBase.
Although that does seem odd behaviour to me. Obviously as the original
implementation was using an array I can see how the implementation drove that
specification.
Non of the JavaFx unit tests test for that specific case as the unit tests all
passed. It would be nice if there was a specific test case for this behaviour.
I would need to store a registration count for each listener to satisfy this
requirement.
On 12 Feb 2020, at 11:34, Jeanette Winzenburg
<faste...@swingempire.de<mailto:faste...@swingempire.de>> wrote:
Zitat von Danny Gonzalez
<danny.gonza...@screamingfrog.co.uk<mailto:danny.gonza...@screamingfrog.co.uk>>:
Hi Ed,
I have submitted a pull request and the branch is here:
https://github.com/screamingfrog/jfx/tree/listeners_optimisation
hmm .. the change seems to be breaking spec of add/remove listeners
"If the same listener is added more than once, then it will be notified more than
once".
or what am I missing?
