Re: Graphics - how to show partial progress.

From:
Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>
Newsgroups:
comp.lang.java.help
Date:
Tue, 18 Dec 2007 15:46:43 -0800
Message-ID:
<xNKdnbPmhqh1xvXanZ2dnUVZ_r2nnZ2d@comcast.com>
rossum wrote:

I am writing a graphics program that calculates individual colour
values for every point, hence it runs rather slowly as the
calculations for each point are somewhat complex. What I want to be
able to do is to show progress-so-far every so often, so the user gets
to see something, rather than a long wait with a blank screen. I know
I can do an updating % progress bar, but I would rather actually show
the progress on the screen so they can see a partial picture while the
next part is being calculated.

I am new to Java graphics, so I am probably missing some obvious
technique here; my google-fu has not found anything relevant to what I
want. In other languages I have used a technique with two Graphics
objects, updating one while displaying the other, but in this case I
cannot find a Component.setGraphics() method. Would it be possible to
do a similar thing with two separate JPanel objects?

The partial code below shows what I am trying, I need a "display and
continue calculating" function that I can call at intervals while
calculating points.

Does anyone have any suggestions?

Thanks in advance,

rossum

[snip code]
What you really want to do is draw to a BufferedImage, and then in your
paintComponent method, paint that image.

Make sure you use proper threading and synchronization, other wise
you'll either block the EDT (and have an unresponsive UI), or you'll end
up with undefined behavior that may appear to work to you, but breaks
everywhere else.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

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