Android gamepad not working

i am using ue4 4.19.2 but when i play game in my mobile phone the gamepad is not working .

i map the input with  raw input generic usb but this not working for me.
please anyone know how to map the input . Or any othere idea how to work with gamepad in android

Is there anyone who know how to fix this issue

Here anyone know how to fix this.

Analog sticks and d pads are working fine. Then i add printstring with all other keys. So when i press any button of gamepad this shows gamepad face button bottom. With left shoulder trigger or others keys show the same msg.