How to work with dual sim cards android?

Question

Java

You need to write software for backup contacts, including those on SIM cards, SMS messages (Incoming and outgoing), and a call log marked SIM1 or SIM2, etc.
API exists only starting from android version 5.1
And what about old people 4.2, 4.4?
Are there any libraries for this task?
And throw a couple of examples from the git hub on the robot with multi-sim, otherwise I didn’t find anything and Google didn’t help :(

Answer 1

At one time, this question was interesting - I opened up some kind of dialer app with xpda and looked. Calls to some undocumented functions through reflection - if I remember correctly. But it seems that it did not work with all multi-sim phones. it was still vendor-specific then. Pleasure is something else, in general.
Take a look - not sure if it's 100% what you're looking for, but there's something there. Like android 4.4 (sdk 19)
https://github.com/dragos-niculescu/dualsim