Presto Mp3 Player is free mp3 player which supports background playing, lock screen control, and working offline.
Google Drive download
Unlimited Playlist support
Controlling from lock screen
In order to transfer your mp3 files over wifi to Presto Mp3 player, tap "Load MP3" button and select WIFI TRANSFER. Browse the URL address which will be generated on your computer. The web page will allow you to select mp3 files from your pc and transfer them to player. Your pc and phone must be using same internet network.
After downloading your files, you will be able to listen them anytime.