Here the problem: my app will generate some files, and I want to give to the users the opportunity to exchange these files between them.

This requires 3 steps:

1. Saving the data: easily **done** in Storage implementing the
functions required by the Externalizable class;
2. Sharing the data: **done** (probably, right now it's impossible to check if the
result is correct because the missing step 3) with the sharing
methods offered by the framework, as soon as I understood I needed
to use as mimetype "application/octect-stream";
3. importing the downloaded data (shared by another user): **this one I can't manage to
find a way to make it work.** Loading the files from the app's Storage
is easy, but accessing to the folders out of the app's Storage is
something I can't manage to do.

I used FileSystemStorage in the hope of gaining access at least to the Download folder that (mostly) every phone has, but apparently I can't manage to accomplish the task

Using the FileSystemStorage on Android, for example, I have access to

* /storage/emulated/0
* /storage/emulated/legacy
* file:///system

The first two being related to the Storage of the app.

Acceding to file:/// I obtain a long list of folders, a partial list including

* media
* logs
* sdcard
* Removable
* ...
* root
* ...

But when I try to access some of these, they all appear to be empty. Either I make some mistake or the app can't see their content.

So I wonder if there is a way to accomplish the task, namely to have access to the files (probably in the Download folder) the user has downloaded, to import them.