It works:
Uri selectedUri = Uri.parse(Environment.getExternalStorageDirectory() + "/myFolder/");
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(selectedUri, "resource/folder");
startActivity(intent);
Have a nice codding :)
EDIT:
If the current solution doesn't help you, then these file/directory choosers libraries can be helpful:
https://android-arsenal.com/tag/35