Strategy game, which way to go?

Hello all
I was wondering, how are all these strategy games made? Like clash of clans, war alert, boom beach… Etc

Are they done with native Android using canvas and drawing?
Or is game engine such andengine or unity used?

I am experienced in native Android but I am not sure if i should do it that way or start learning an engine?

Ps: I am not familiar with opengl

Thank you so much

You can make such game with only canvas.
Use some engine like Unity, Libgdx, Cocos2d-x to make game, with those engine you can make game without know what opengl is.
Unity have some asset help you make Strategy like City-Building Game Kit for Unity3D - How to make a Unity Social Game

Almost certainly they use some game engine, although some might be in-house made specifically for that game. Going into native Android for games has only disadvantages - block you from porting it to other systems for example.

Thank you @hackformore and @Magnesus for the comments. I was not looking to start on OpenGl for sure. For me either do the game in Canvas and the typical onDrow/imageview kind of thing or start learning unity. My only worry with Unit and other engine that (maybe I am wrong!) they don’t let you use native android features. For example Toast, dialog, bluetooth…etc .That’s why I am leaning for the native development ,yet most people use unity so I feel I am missunderstanding it.
What’s your opinion?

You can do what you want, all of them have invoke/access to native code.