What maps for android can be used offline?

Question

Android

Hello!
Prompt for a map library for android applications that would meet the following requirements:
1. Works offline.
2. There is navigation.
3. You can create selected areas on the map, by coordinates.
4. For areas, you need the ability to make heat maps.
The application is focused on use outside the city, in the fields.
Please tell me which libraries can be used.

Answer 1

mapsforge

Answer 2

The Osmand and Maps.Me applications have open source codes, navigation is present. Learn, use.