Spotlight: Fileseal is a user-friendly automatic file encryption app for Android
Specifying a target folder means both existing and newly added files inside the folder and its subfolders will be automatically encrypted, stored in the target folder under encrypted sub-folders and syncing with cloud services, should you choose so.
Files uploaded to cloud services are universally encrypted, while the original and un-encrypted files are erased immediately using secure delete methods, minimising the chance of recovery after removal. Fileseal also contains a built-in image viewer and a rudimentary file manager, letting you see and manipulate photos without exposing them to external applications.
Fileseal is free to use, and contains an optional Premium upgrade. The steep $15 price of admission will unlock multiple folder protection, ad removal, an increase of file size limit, extended mode for secure-deleted files, and other things.