Jack wrote:
> Right now my test program uses a very simple method: I have a handler
> that is called to start the animation. The handler's handleMessage()
> method calculates the new frame, invalidates the view, and calls
> sendMessageDelayed(obtainMessage(0), 50);
>
> However, the animation isn't smooth - especially, for some reason, in
> landscape mode. Portrait mode seems much better (on a G1, if it
> matters).
That is to be expected.
> This suggests to me that this isn't the right way to... handle... this
> problem. What would be a better way?
You can think of the main application ("UI") thread as being a message
loop driven by a message queue. Whenever you call setText() or
invalidate() or whatever, you are really putting a message on that
queue. That queue's messages are processed whenever Android isn't
executing your code (e.g., callbacks like onCreate() or onClick() or
handleMessage()).
What your sendMessageDelayed() is doing is putting a message on the
queue with a time associated with it. Android will ignore that message,
even if it is at the head of the queue, until that time elapses.
However, just because the time has elapsed does not mean that it will
get executed immediately, because Android may have moved on to other
messages, or be in your code, or whatever.
Hence, sendMessageDelayed() or postDelayed() or kin will result in some
degree of choppiness, depending on what else is going on.
This is a chunk of the reason for AnimationDrawable and the Animation
classes -- they will give you smooth animations.
> Starting
> a new thread whenever the animation starts and having it repeatedly
> calculate and invalidate instead of relying on the handler, even
> though it means creating and destroying a new thread every time?
That wouldn't help, because you cannot update the UI from the background
thread. All the background thread will do is wind up telling the UI
thread, via a message on the queue, to go do something.
--
Mark Murphy (a Commons Guy)
http://commonsware.com | http://twitter.com/commonsguy
Android Training in US: 14-18 June 2010: http://bignerdranch.com
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