Keeping an oft-redrawn interface interactive by preparing drawing in thread

Question

Hi!
I require rapid updates (say, every 0.1 s) to several UIViews which reflect the state of constantly-changing model objects. Doing the updates on the main thread blocks the interface pretty quickly, so I tried to move the main drawing code to a thread which renders to an image, which is then drawn later on the main thread.
I'm getting EXCBADACCESS errors on -\[UIImage drawAtPoint:\], however.
CGSize size = \[self frame\].size;
UIGraphicsBeginImageContext(size);
UIImage *img = \[UIImage imageNamed:@"MyImage.png"\];
[img drawAtPoint:CGPointZero]; // EXCBADACCESS here
And the backtrace:
#0 0x3104ee65 in CGSBlendBGRA8888toARGB8888 ()
#1 0x31186b49 in rgba32_image ()
#2 0x00560e12 in ripl_Mark ()
#3 0x00563328 in ripl_BltImage ()
#4 0x0054e9d1 in ripc_RenderImage ()
#5 0x0055d997 in ripc_DrawImage ()
#6 0x30fef3f5 in CGContextDrawImage ()
#7 0x30a676ba in -\[UIImage drawInRect:blendMode:alpha:\] ()
#8 0x30a65013 in -\[UIImage drawAtPoint:blendMode:alpha:\] ()
#9 0x30a64f92 in -\[UIImage drawAtPoint:\] ()
I also noticed that I'm sometimes getting EXCBADACCESS on the main thread, in unrelated drawing code. It would appear that the creation of the image context is app-global, and causing trouble for other drawing routines.
So, my question is this: What's the accepted solution to keep an interface interactive, while providing frequent view updates? If I was writing an OS X app, I'd do the above, using -\[NSImage lockFocus\] and -\[NSImage unlockFocus\]. No joy here, though!
It seems my only path at this point is to do the compositing manually, with the underying char arrays of the bitmap images. That's nasty, though.
Many thanks in advance

Answer 1

I'm not reading that either, but to help you for next time:
- use more than 1 sentence to describe your problem
- only post the RELEVANT code, or a small test program with the same problem if possible.
At least you formatted it, I'll give you that.
Cheers,
Radish21
PS. I think in this case, posting another (better worded) thread might be a good idea, because no one is going to read this one. In general though, don't :)