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

[Alexander Potochkin]

Hello Florian

Thank you for the constructive examples!

I looked at the usage of prototypeCellValue property,
following the JList.updateFixedCellSize() method

I found this code in the 
DefaultListCellRenderer.getListCellRendererComponent():


	if (value instanceof Icon) {
	    setIcon((Icon)value);
	    setText("");
	}
	else {
	    setIcon(null);
	    setText((value == null) ? "" : value.toString());
	}

It means that value always can be an icon,
so we need to do something about that

I also think that shouldn't generify prototypeCellValue,
since it doesn't give as any visible advantage,
moreover some programmers may use an object of a special type
that toString() method returns something meaningful for prototypeCellValue

Thanks
alexp

> Here is a second sample.
> 
> It's not really a  real-world sample, but should be useful to show that also JList of other "value" 
> types than String, such as Integer, Long and Short, can profit from generics.
> 
> It also shows why JList should specify
> ListCellRenderer<? super E> cellRenderer
> 
> rather than
> 
> ListCellRenderer<E> cellRenderer
> 
> (Here: a common Number-cell renderer is used.)
> 
> -Florian
> 
> Am Dienstag, 3. März 2009 schrieb Alexander Potochkin:
>> Hello Tom
>>
>> It's nice to see you here
>>
>>>> Could you please provide a complete example of a JList
>>>> with a custom ListCellRenderer that proves that renderer should be
>>>> generified
>>> I bet if you used NetBeans to find implementations of ListCellRenderer
>>> even within the JDK most useful implementations would cast the value
>>> argument.
>> anyway, it is always better to have a fixed set of examples to discuss
>>
>>> (I prefer option 3, btw.)
>> Thanks
>> alexp
>>
>>> Tom Hawtin
> 
>