How can I answer phone calls with a real (like power) button?

I can close phone calls with that button by default, but for me it would be even more useful to be able to answer a phone call the same way. Is there a setting or an application that would enable that? The main idea is to be able to answer a call without interacting with the touch-screen, but only with the real buttons. This is a Xiaomi a2 phone, not rooted.