On Mar 31, 2008, at 2:06 PM, Mike wrote:
I suppose it's possible. The spawned thread does a lot of setup then
iterates some arrays of a bunch of objects in the filesystem that it
needs to delete. The idea is to update the progress bar one
increment with each item being deleted. I'm using a MacBook 2.16 Ghz
but I doubt that the main thread is too slow to be able to do the
updates.
The issue wouldn't be the main thread being too slow, but the worker
thread being too fast, as it were. You'd be surprised how often you
can be wrong with this kind of stuff. I've wasted hours thinking "It
surely can't be x" and then actually measuring and finding it was x
all the time. How big is the bunch of objects your program needs to
delete? How long does it take to delete one item?
Also, I set a message text item with the name of each item being
deleted in the window as the worker thread runs. I never see it
change even for an instant. I find it hard to believe that there
can't be any visual update no matter how quickly the worker thread
completes.
If you change the UI values with setNeedsDisplay: calls, they only get
updated once in every iteration of the main run loop. If there's a lot
going on on that run loop, you may see just one value change (the last
one) or none at all if you reset the values when you're done. If
you're using bindings I'm not sure about the timing, but it's
definitely not going to be faster than direct calls.
Have you measured how long it takes for your worker thread to complete
its task? If it's less than a second, I'm not sure if you need a
progress bar at all. A progress bar combined with changing text
doesn't make a lot of sense if that updates faster than your user can
read anyway, so you might want to tone down the update speed.
Hank
Hank Heijink (Mailinglists) wrote:
Just checking the obvious here - is it possible that your worker
thread completes its work so fast that the main run loop hasn't
updated the screen once before it's done? Keep in mind that the
main thread has to display your window with the progress bar and
the text and (depending on your implementation) that your worker
thread may be working (and completing) while that's being done.
On Mar 30, 2008, at 2:55 PM, Mike wrote:
I have all my UI running on my app's main thread. I have a worker
thread that I detach with
detachNewThreadSelector:toTarget:withObject: (my worker thread).
In my worker thread I do a tight processing loop and one of the
things I do in the loop is call two methods in the main thread to
update the display (a text message and progress bar) - via
performSelectorOnMainThread:withObject:waitUntilDone:modes.
However, when the loop runs in the spawned thread, the display
doesn't get updated. If I insert a sleep(1) call into the loop,
then the display updates.
Why doesn't the main thread process the changes to the UI unless I
call sleep? I thought the whole idea of using a separate thread
was so that the main thread could continue to run on its own?
Thanks,
Mike
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