Get folders name from Assets directory

I'm trying to get the names of my folders in "assets". I can get the names of the files with an AssetManager by using the method assetManager.list(). But the problem is that it return only files' name and not folders' names. So I'm trying to use the listFiles() method but i can't access to the Assets directory; I've try the following :

File dir = new File ("file:///android_asset/");
File[] files= dir.listFiles();

But it doesn't work :( ... Is there a way to get the folders' names contained in the Assets directory ?

Copyright Notice：Content Author:「Nox」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/3281245/get-folders-name-from-assets-directory