Recently I found a fancy library that does this thing.
Or you can look up for your own.
There was, a country code picker extension by Deep Host, but that requires downloading an app, and we cannot guarantee whether their extension works because he usually does not support them. Hence, I am putting this suggestion here.
I have seen this before, what I mean is a list of countries.
The user used a JSON file to store countries, but I am thinking about a spinner dialog of countries that can display country flag images. ListViews can display images, but I am thinking a spinning dialog of country codes.
It's really a great idea, about 2 months before I had the same idea and planned to make new extension for this and also found the same library you have, but it's not possible to make extension with this library, as it uses so much of XML stuff, i have found one more library and I'll start working on it after 19 March(as it's the last date of my examination)