ContactsMethod.kt

private fun contacts(): Flowable<SimpleContact> =
        Flowable.generate<SimpleContact, Cursor>(
                Callable<Cursor> {
                    contentResolver.query(Contacts.CONTENT_URI,
                            arrayOf(Contacts.DISPLAY_NAME, Contacts.STARRED),
                            null, null,
                            "${Contacts.DISPLAY_NAME} ASC")
                },

                BiFunction<Cursor, Emitter<SimpleContact>, Cursor> { cursor, emitter ->
                    if (cursor.moveToNext()) {
                        emitter.onNext(SimpleContact.from(cursor))
                    } else {
                        emitter.onComplete()
                    }
                    return@BiFunction cursor
                },

                Consumer<Cursor> {
                    cursor -> cursor.close()
                }
        )