There is QuickOffice app on Android (it comes preinstalled on some, and is also available on other platforms). Be aware that if you use its cloud storage functionality that an access token is sent to one of their servers which then accesses the actual cloud server (Google Docs, Dropbox etc). This is not disclosed in any way.
What it means is that when their servers get hacked, the hackers will have full access to any storage you provided the credentials for. For all you know, they already do.
I've been back and forth with their support, with their latest statement being this nonsense: "However, I've been told that we are doing our cloud storage access in a very secure way, even more secure than accessing same cloud storage via web browser or native application."
Be afraid, very afraid.