I just installed MAME4droid 0.39u1 on my Bravia X800D running Marshmallow 6.0.1. Copied some roms across to the correct folder and they're found, looks promising so far.
Paired a DualShock4 to the TV via bluetooth and then tried to start mame up. In default input mode the left analog stick works to move up and down in the mame rom list but no button seems to work to start the game. Also tried using the remote and plugging in a keyboard via USB, no luck.
Is there any way to get this working? If necessary I can buy a generic android controller (iCade ?) instead of the dualshock 4. would like to get this working and it's so close... frustrating !
(also have a PS3 controller if there is any way to make that work)
Haven't tried it with my Nvidia Shield TV but I had to use Sixaxis for my phone to get the correct button mapping, but that requires root. Last time I tried a DS3 controller I had to use Sixaxis again to get everything working. Might be due to proprietary coding required for the controllers to properly connect with the correct button mapping.
A generic controller will work as long as it uses standard bluetooth, I had a Moga Pro which worked fine with all the console emulators I tried.