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Re: art of writing a resp

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  To: comp.lang.java.programmer
Wesley Hall wrote:
> Timasmith wrote:
> > Having played around with someones variant of Swingworker I have found
> > pleasing results with using a background thread for actions initiated
> > by a table, tree or menu.  Clicking on the said item kicks off the
> > action while letting the gui items respond appropriately.  In fact
> > rather than hardcoding it everywhere I extended an ActionListener to do
> > just that.
>
> Just remember that Swing is NOT thread safe so any updates you do to
> visual components should be done on the AWT thread. It is OK to use a
> thread to go off and fetch data etc, but when the data returns and you
> want to display it you must use SwingUtilities.invokeLater to update the
> GUI as you will get occasional strange behaviour.
>
> > Now when it comes to buttons there is a different story.  When you
> > press a button you want a good solid push but with the background
> > thread I get a bouncy button that immediately springs back to its
> > position - too quickly in my estimation.  Since the action it is
> > performing may be quick or slow its difficult to guage the slow ones
> > only for background processing.
> >
> > I guess I could introduce an artifical pause for the button but any
> > other ideas on that.
>
> Not really, it has been a while since I did any swing but presumably the
> button stays 'pressed' for as long as the action listener is running. If
> you are making that run very short with threading, it is not suprising
> that this is happening.
>
> You would be better of forking a thread to go a fetch data from the
> server and having the action listener prepare the GUI for when the data
> comes back, so if you are hitting a button to display a dialog, build
> the dialog in memory on the AWT thread while your worker goes of and
> fetches the data. If your GUI builds before your data comes back use the
> classes in java.util.concurrent to synchronize the threads, then use
> invokeLater to pass the data to the dialog, display the dialog and
> return from the action listener.
>
> In doing this, you are finding a balance between single threading (where
> the time delay is building gui time + collecting data time), and doing
> everything in another thread (which, on the AWT thread is almost 0 time
> and makes your button look like it isnt doing anything). What you have
> instead is a button that remains depressed for however long the data
> fetch takes (without gui building time which is happening concurrently).
>
> You could also consider showing the dialog as soon as it is built and
> have the fields populate when the data comes back. This will give your
> application a very responsive real (with all clicks responding visually
> in a fraction of a second) but you could end up with dialogs that look
> empty for a few seconds if the dialog builds much before the data is
> returned.
>
>
> > Is there a way to flip the hourglass regardless of the control you are
> > waving over?  Gets a little complex perhaps as you might want to
> > hourglass one frame but not another.
>
> I seem to remember hourglass cursors being a bit of a pain in the neck.
> There was a nice java tip on javaworld that enabled you to push an
> action handler on the event queue so that any event that took over x
> amount of time would automatically flip the cursor. This was much nicer
> than doing it manually for every button click... lets see if I can find
> it...
>
>
> Yup... here it is... its a bit old now (published in 2000) but should do
> the job. There could be a more modern solution, but I am a little out of
> the loop as everyone seems to want web apps these days...
>
> http://www.javaworld.com/javaworld/javatips/jw-javatip87.html
> 
> Have fun.

Thanks, great tips - I can't wait to do them.

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art of writing a responsi "Timasmith" <timasmith@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000
  Re: art of writing a resp "Wesley Hall" <wesley.hall@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000
    Re: art of writing a resp "Timasmith" <timasmith@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000
    Re: art of writing a resp "Fred Kleinschmidt" <fred.kleinschmidt@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000
  Re: art of writing a resp "Andrew Thompson" <andrew.thompson@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000
    Re: art of writing a resp "Lew" <lew@THRWHITE.remove-dii-this> - 2011-04-27 15:26 +0000

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