Implementing Searchview, Recyclerview with checkbox

I am creating an app that allows the user to create a groupchat and Im using firebase to store all the data. Now I am facing an issue about searching a friend to add to group. Inside my layout there's a searchview(from here), custom recyclerview with checkbox. So my question is:

1. How to saved a checkbox state even if I use a searchview to search for users?
2. Is there a library/source code for that because I want to make my code simple and clean (Note: I am using firebase)

Here is my code for that (link). Feel free to comment anything or suggest to improve it.