You're never going to have a truly cross platform tool set. The UI/UX paradigms are just too different. There are already several solutions for sharing library

You're never going to have a truly cross platform tool set. The UI/UX paradigms are just too different. There are already several solutions for sharing library code for business logic between the platforms, either using C++, or compiling Java to Objective-C, and that's about as good as you're gonna get.