Ask HN: What are some good android apps to encrypt files on android?

There is Encryptr - simple and easy to use. It stores your sensitive data — like passwords, credit card data, PINs, or access codes — in the cloud. https://play.google.com/store/apps/details?id=org.devgeeks.e...

I suggest looking at the apps and tools developed by the Guardian Project https://guardianproject.info/code/

There was an encrypted note-taking app but it's not developed any more.

The generic solution is to use GnuPG.