[freemarketteddy]

I think one subtle difference is that in iOS there is some degree of parallelism even in the UI Updates as they happen in the NSRunLoop of the main thread(main NSRunLoop).

So that an UI Update that is waiting for hardware can be delayed and the next UI update in the loop can be processed.

I dont seem to recall any such pattern for Java main thread UI Updates.

[saurik]

An NSRunLoop is normally a CFRunLoop, and a CFRunLoop is pretty much just "get next task; run that task; loop": if one task blocks, it cannot run the next one; the only way for it to look like it is doing multiple things at once is for code to reenter the runloop using CFRunLoopRun(), which is hardly ever used (it increases the size of the stack pretty quickly and breaks assumptions about single-threaded concurrency). Any concurrency with hardware compositing is going to happen at the kernel or hardware levels, not in the app.