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Re: Update GUI while JSli

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  To: comp.lang.java.gui
Chris Smith a ocrit :
> Philipp <sicsicsic@freesurf.ch> wrote:
>> Knute Johnson a ocrit :
>>  > You need to take a look at JSlider.getValueIsAdjusting().  With this
>>  > method you can test in your ChangeListener whether the slider is
>>  > moving.  If it is, don't bother to update your GUI until it stops.  Or
>>  > make occaisional updates while it is moving.
>>
>> I want to update my GUI only when the slider is moving. So your second 
>> solution, ie. making occasional updates seems adapted.
>>
>> How could I implement that? Maybe I can just compare the present time to 
>> the last repaint time and if the differenc is above a value (say 0.1s), 
>> call a repaint. Is this good design (especially with this hard coded 
>> value of 0.1 s)?
> 
> Repaint events are coalesced in the event queue automatically by the 
> event queue implementation, so I think you're doing more work than 
> necessary.  Just call repaint() from the ChangeListener, and repaint in 
> paintComponent.  This will update as often as possible, but no more 
> often, so the most lag you'll get is the time required to paint once.  
> The effect described upthread, where the painting falls behind and 
> catches up in steps, can't occur with repaint events.
> 
> A way to mess this up is to do significant calculation in the 
> ChangeListener in addition to calling repaint() and let those get behind 
> regardless of painting.  If this is a problem, you could try to avoid 
> the issue by setting flags that arrange for the calculation to be done 
> in paintComponent instead (of course, storing the result so you don't 
> repeat the calculation for EVERY repaint).
> 
> (If the calculation is TOO expensive, then it should be moved into an 
> alternate thread; but if that's needed, you have no reasonable hope of 
> updating your GUI as the slider is moving anyway.)
> 

Thanks for your very complete answer. I think I will end up implementing 
your last solution. The one with a different thread. This also because 
the repaint method cannot be easily adapted to do the computation.

Philipp

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Update GUI while JSlider "Philipp" <philipp@THRWHITE.remove-dii-this> - 2011-04-27 15:35 +0000
  Re: Update GUI while JSli "Andrew Thompson" <andrew.thompson@THRWHITE.remove-dii-this> - 2011-04-27 15:35 +0000
  Re: Update GUI while JSli "Andrew Thompson" <andrew.thompson@THRWHITE.remove-dii-this> - 2011-04-27 15:35 +0000
  Re: Update GUI while JSli "Chris Smith" <chris.smith@THRWHITE.remove-dii-this> - 2011-04-27 15:35 +0000
    Re: Update GUI while JSli "Philipp" <philipp@THRWHITE.remove-dii-this> - 2011-04-27 15:35 +0000

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