Try this code to return all storage folder name.
Mark my post here:
fooobar.com/questions/36365 / ...
Do not forget to add permission.
Accessing external storage
To read or write files to external storage, your application must have the READ_EXTERNAL_STORAGE or WRITE_EXTERNAL_STORAGE system permissions. For instance:
<manifest ...> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> ... </manifest>
source share