Access files on OneDrive by my APP -- 2

I have an Android App, written in Basic4Android (i.e. Java based language), that needs to download files stored in OneDrive space of a customer of mine. I need assistance on this subject. The ideal should be a lib or an object callable by my code, but we can also examine other ways, like doing a stand-alone App for doing the task. Being neophite of this subject, some preliminary discussion is necessary to decide further details.