<Swing Dev> 6179357: Generics: JList: ListCellRenderer & prototypeCellValue

[Florian Brunner]

Ok, I'll think about some examples.

-Florian

Alexander Potochkin schrieb:
> Hello Florian
>
> I must confess that I don't think it is desirable
> to generify every class in Swing, so #1 looks good for me
> :-)
>
> Two generic parameters add to much of typing, in my opinion
>
> Could you please provide a complete example of a JList
> with a custom ListCellRenderer that proves that renderer should be 
> generified
>
> By the way the more examples the better,
> another one which promotes JList generifying
> would also help to promote this idea for Swing team members
>
> Thanks
> alexp
>
>> So, 2 votes for option 3), which is a reasonable one, I think.
>>
>> Pavel? Anyone else?
>>
>> -Florian
>>
>> Am Sonntag, 22. Februar 2009 schrieb Erik Lundqvist:
>>> Hi,
>>> ListCellRenderer should absolutely be generic which rules out option 
>>> 1 :)
>>> I cannot remember ever using the prototypeCellValue so a bit worried 
>>> about
>>> saying too much about how people are using it, but it does not seem
>>> unreasonable that it should be of the same type so I would go for 
>>> Option 3
>>> as well which seems the simpler and most common use case.
>>>
>>> //erik
>>>
>>> 2009/2/21 Florian Brunner <fbrunnerlist at gmx.ch>
>>>
>>>> Hi,
>>>>
>>>> I think adding generics to the ListCellRenderer could also be 
>>>> useful. The
>>>> problem is that in JList
>>>> the same cell renderer is used for the items as for the
>>>> prototypeCellValue - and the
>>>> prototypeCellValue doesn't necessarily have be of the same type as the
>>>> items!
>>>>
>>>> So I think we have 3 options:
>>>>
>>>> 1) Don't provide a generic cell renderer/ allow only Object as 
>>>> parameter
>>>> for the cell renderer in
>>>> JList.
>>>>
>>>> 2) Add a second generic parameter. Eg. something like:
>>>> class JList <E, P super E>{ ... }
>>>>
>>>> and use P for the prototypeCellValue property as well as for the cell
>>>> renderer.
>>>>
>>>> 3) Require prototypeCellValue to be of type E. In the probably rare
>>>> cases, where this is a problem
>>>> one can still specify a common base class of the items and the
>>>> prototypeCellValue as the generic
>>>> parameter or use a raw type JList.
>>>>
>>>>
>>>>
>>>> I think it would be a pity not to provide a generic cell renderer 
>>>> (1) and
>>>> think 2) is inconvenient
>>>> and confusing, since in my experiences prototypeCellValue is only used
>>>> rarely.
>>>>
>>>> So I'm voting for 3). For which option do you vote? For which reason?
>>>>
>>>>
>>>>
>>>> Note I also propose to use:
>>>>
>>>> ListCellRenderer<? super E> cellRenderer
>>>>
>>>> rather than
>>>>
>>>> ListCellRenderer<E> cellRenderer
>>>>
>>>> in JList. This would make it more flexible. Do you agree? (It's 
>>>> actually
>>>> the first time, I think, I
>>>> use 'super' with generics myself, but I think this is a good use 
>>>> case of
>>>> it. So any comments are
>>>> welcome. ;-) )
>>>>
>>>> -Florian
>>
>>
>