How to access Android Lollipop DocumentFile files

Question

How is it possible to access files which are generated from a DocumentFile in Android KitKat/Lollipop in Native JNI Code, so I can use fopen, fread, etc. I'm particular asking this to access the external SD-Card files via the NDK.

Answer 1

You can use file descriptors:

ParcelFileDescriptor filePfd;
DocumentFile file;
filePfd = getContentResolver().openFileDescriptor(file.getUri(), "w");
int fd = filePfd.getFd();

This int fd can be passed to JNI and used as usual C++ file descriptor:

FILE* file = NULL;
file = fdopen(fd, "r+b");

And you need permission to access to file or directory on SD-card