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Re: Update GUI while JSli

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  To: comp.lang.java.gui
Philipp <sicsicsic@freesurf.ch> wrote:
> Knute Johnson a écrit :
>  > 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.)

-- 
Chris Smith

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Thread

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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