Hi Johan,
100 is an integer according to the Java specs, so I guess it was a bug in RoboVM.
Is there a reason why you are accessing the NSMutableDictionary using the Core Foundation methods instead of just converting it when necessary for the CGImageSourceCreateThumbnailAtIndex()?
Also, you should not call dealloc() or release() on Objective-C objects, these will be handled by the Java GC and NatJ automatically. We are thinking of removing these methods from future versions of the bindings so they are not confusing anyone.
There could be cases, where you are allocating a lot of huge native objects in a tight loop, that are not used afterwards, and the Java GC may take too much time to release them (meaning that iOS may kill your app due to high memory usage before that happens), then you can call ObjCRuntime.disposeObject() to force the disposal of the native peers. But this is the exception to the rule and should not be used in most cases.
Best Regards,
Gergely