In order to be able to access (read / write) media files on the external storage, the following permission must be declared in the manifest:
“android.permission.WRITE_EXTERNAL_STORAGE”
If you only need reading rights, this is enough:
“android.permission.READ_EXTERNAL_STORAGE”
Usually, each component / extension automatically asks for these permissions, if needed.
Note: WRITE_EXTERNAL_STORAGE is sufficient as it implicitly grants READ permission.