space-android/res/xml/exposed_filepaths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="file" path="/" />
    <!-- yes, valid for ALL external storage and not only our app folder, since we can't use @string/data_folder
    as a value for 'path' attribute; in practice, we will only generate URIs in our folders, of course -->
</paths>