On Sun, Aug 30, 2009 at 2:48 PM, Nick_Zaillian <[email protected]> wrote:

> Okay, actually, you can disregard that last comment.
> "Thou shalt not modify the UI from a background thread, for that is
> the way of sin" pretty explicitly gives me my answer.   I gotta say,
> this is pretty inconvenient.  Must be the reason that Electrum Drum
> Machine (the only other Android drum sequencer I've seen) doesn't give
> the user any visual indication of playback position.


Do your time critical stuff in a separate thread.  Post messages to the main
thread when there is something interesting it has changed for it to redraw.
Or if you know you will be continually drawing, have your main thread
continually running a draw loop where it draws whatever the current state is
in onDraw() (but you will probably pay the price of more CPU usage for
this).  Or if you really want to, use a surface view to have a dedicated
part of the UI that another thread can redraw outside of updates (but you
are going to need to be much more careful about threading and other issues
if you do this).

It is perfectly possible to use the framework to have a UI update while
doing background audio stuff.  Heck, the media player does this just fine,
as do many other apps.

-- 
Dianne Hackborn
Android framework engineer
[email protected]

Note: please don't send private questions to me, as I don't have time to
provide private support, and so won't reply to such e-mails.  All such
questions should be posted on public forums, where I and others can see and
answer them.

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