<Swing Dev> [11] Review Request: JDK-5076761 : JList.setSelectedValue(null, ...) doesn't do anything

[Semyon Sadetsky]

On 01/05/2018 10:16 PM, Sergey Bylokhov wrote:

> On 05/01/2018 18:01, Semyon Sadetsky wrote:
>> Can you explain what is wrong with the suggested  approach?  It is 
>> flexible to handle both null and non-null containing JList.
>
> Because it is wrong direction try to support some approach which is 
> undefined behavior. The null has a special meaning in 
> JList.getSelectedValue/setSelectedValue() as well as in a few other 
> methods mentioned below. The usage of unspecified null values may 
> result in a run time exception either immediately or at some later time.
I didn't find any spec that mentions null as a special value as well as 
any pointer that JList couldn't contain null.
getSelectedValue() may not be an indicator because there are several 
replacements setSelectedIndex(), setSelectedIndices(), 
getSelectedValues(), getSelectedValuesList() which supports null.
Other components are unrelated.
>
>>
>> On 01/05/2018 04:25 PM, Sergey Bylokhov wrote:
>>> I doubt that support of null values in the data model is intentional 
>>> because JList is "A component that displays a list of *objects* and 
>>> allows the user to select one or more items."
>>>
>>> The null behavior was not specified and work in most cases because 
>>> some of the getXXX methods in ListModel sub-classes and JList have a 
>>> special meaning of null:
>>>
>>> JList.getSelectedValue(): Returns {@code null} if there is no 
>>> selection.
>>> ListModel.getElementAt(int index): In most cases implemented to 
>>> return null if index is incorrect.
>>>
>>> Similar method TableModel.getValueAt(int,int) is also usually 
>>> implemented to return null if value is not found or some error occured.
>>>
>>> JComboBox.setSelectedItem(): use <code>null</code> to clear the 
>>> selection
>>> ComboBoxModel.setSelectedItem(): <code>null</code> to clear the 
>>> selection
>>> ComboBoxModel.getSelectedItem(): <code>null</code> if there is no 
>>> selection
>>>
>>> So I suggest to follow initial intention here, because it is too 
>>> late to add validation of the values.
>>>  - The null value in get() will mean no-selection.
>>>  - The null value passed to set() will clear selection.
>>>
>>> On 05/01/2018 02:15, Pankaj Bansal wrote:
>>>> Hi Semyon/Sergey,
>>>>
>>>> Yes, JList can contain null elements as it can be added to data 
>>>> model. I think this changes a lot in this bug. I think the 
>>>> selection needs to be cleared when the object passed is not present 
>>>> in the list, irrespective of it being null or not. I have made code 
>>>> changes. Please have a look.
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~pbansal/5076761/webrev.02/
>>>>
>>>> Regards,
>>>> Pankaj Bansal
>>>>
>>>> -----Original Message-----
>>>> From: Semyon Sadetsky
>>>> Sent: Friday, January 5, 2018 6:59 AM
>>>> To: Pankaj Bansal; swing-dev at openjdk.java.net
>>>> Subject: Re: <Swing Dev> [11] Review Request: JDK-5076761 : 
>>>> JList.setSelectedValue(null, ...) doesn't do anything
>>>>
>>>> Hi Pankaj,
>>>>
>>>> Can JList contain null value?
>>>>
>>>> --Semyon
>>>>
>>>>
>>>> On 01/02/2018 11:26 PM, Pankaj Bansal wrote:
>>>>> Hi Sergey,
>>>>>
>>>>> Thanks for the review.
>>>>>
>>>>> I have made the suggested changes. Please have a look.
>>>>> webrev: http://cr.openjdk.java.net/~pbansal/5076761/webrev.01/
>>>>>
>>>>> Regards,
>>>>> Pankaj Bansal
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: Sergey Bylokhov
>>>>> Sent: Wednesday, January 3, 2018 3:31 AM
>>>>> To: Pankaj Bansal; swing-dev at openjdk.java.net; Prasanta Sadhukhan
>>>>> Subject: Re: [11] Review Request: JDK-5076761 :
>>>>> JList.setSelectedValue(null, ...) doesn't do anything
>>>>>
>>>>> Hi, Pankaj.
>>>>> The fix looks fine, but I suggest to update the spec as well and 
>>>>> describe the behavior if "null" value is passed.
>>>>>
>>>>> On 02/01/2018 02:07, Pankaj Bansal wrote:
>>>>>> Hi All,
>>>>>>
>>>>>> Please review the fix for JDK 11.
>>>>>>
>>>>>> Bug:
>>>>>>
>>>>>> https://bugs.openjdk.java.net/browse/JDK-5076761
>>>>>>
>>>>>> Webrev:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~pbansal/5076761/webrev.00/
>>>>>>
>>>>>> Issue:
>>>>>>
>>>>>> When setSelectedValue is called on JList with null object, it should
>>>>>> clear all selection. But it is not doing anything.
>>>>>>
>>>>>> Fix:
>>>>>>
>>>>>> In setSelectedValue if the object is null, the setSelectedIndex is
>>>>>> called with -1. but this does not clear the selection. We should be
>>>>>> calling clearSelection instead of SetSelectedIndex.
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> Pankaj Bansal
>>>>>>
>>>>>
>>>>> -- 
>>>>> Best regards, Sergey.
>>>>
>>>
>>>
>>
>
>