Dropbox has some mobile apps that have some fairl complex client-side logic with multithreading (https://tech.dropbox.com/2014/04/building-carousel-part-i-how-w

Dropbox has some mobile apps that have some fairl complex client-side logic with multithreading (https://tech.dropbox.com/2014/04/building-carousel-part-i-how-we-made-our-networked-mobile-app-feel-fast-and-local/ https://tech.dropbox.com/2014/04/building-carousel-part-i-ho...), so they use a cross-platform C++ library with bindings to Obj-C and Java with their Djinni library (https://github.com/dropbox/djinni/ https://github.com/dropbox/djinni/)