In my recent project, I am storing my settings.xml file to the default download path in android mobile. What I found is that it fetches all the data from that file and displays in my application perfectly till android version 5(i.e; till Lollipop). When I try the same thing in Android 6(i.e; Marshmallow), It gives me error saying "Device not open". I do know why this thing happens. It's because of new "app permissions" concept since android version 6. So what I did was manually go and switch on the app permission for storage for my app and it worked.

So there has to be something for this new "app permissions" concept that lets developer ask users to switch on permission like android studio does for android app development.