Android Scoped Storage

How can I request premission to acess a folder ?

val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE).apply {
            flags = Intent.FLAG_GRANT_WRITE_URI_PERMISSION or Intent.FLAG_GRANT_READ_URI_PERMISSION or
                    Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
        }

startActivityForResult(intent, OPEN_DIRECTORY_REQUEST_CODE)

How can I obtain an InputStream from a file Uri ?

 val p: ParcelFileDescriptor = contentResolver.openFileDescriptor(fileUri, "r") ?: return null

 val reader = BufferedReader(InputStreamReader(FileInputStream(p.fileDescriptor)))

How can I obtain an OuputStream from a file Uri ?

 val p: ParcelFileDescriptor = contentResolver.openFileDescriptor(fileUri, "w") ?: return false
 val outStream =  OutputStreamWriter(FileOutputStream(p.fileDescriptor)) 

How can I request permission persistance to a parent Uri ?

    // Request persistence
    val takeFlags: Int = Intent.FLAG_GRANT_READ_URI_PERMISSION or
            Intent.FLAG_GRANT_WRITE_URI_PERMISSION
    // Check for the freshest data.
    contentResolver.takePersistableUriPermission(uri.data!!, takeFlags)