I put my car in my centre console. If I get a call, I swipe and it answers. When the person on the other end hangs up, the phone app closes and the phone goes back to a black screen.

If you root the phone there are other things you could change. But I can't think of any way you can get the phone in your pocket to answer calls without any action whatsoever....and without leaving the screen active in your pocket.

You could use the headphone cord (not bluetooth) and use the button on the headphone cord to answer calls.

 

How about if you just take the phone out of your pocket when in the car?