Davide,
I know, it’s sad, but to the best of my knowledge, you can’t develop native Android applications with Eclipse anymore.
At Genuitec, MyEclipse has included a couple of Mobile app development solutions, but unfortunately they had to be discontinued – you can read about them here: https://www.genuitec.com/forums/topic/phonegap-support-in-myeclipse-2016/
What you should still be able to do with Eclipse, is hybrid application development, the above link has some tips.
Hope this helps!