On Android 4.4.2 Environment.getExternalStorageDirectory().getPath() returns /storage/emulated/0 but this path does not exist on my Nexus5 Android
Sometimes /storage/emulated/0 can be written to, but reads fail... so tests for "writability" are not sufficient. This is such an annoying problem, I have come up with an equally annoying but effective solution. Hardcode "/mnt/sdcard" Yea, I said it.
Looks like someone else said it first ... storing android application data on SD Card
More joy... http://forums.bignerdranch.com/viewtopic.php?f=414&t=7407