adb error in android studio

Question

I've tried every proposed solution on the internet and nothing is working. Android studio was working fine then one day out of nowhere it kept giving me this error on every project

unable to locate adb

I tried navigating to my adb.exe and kill-sever and restart it but the adb.exe directory is not in my platform-tools folder under sdk.

I've tried uninstalling android studio and reinstalling it. A post suggested that it could be my AVG security but that was not the issue. I've tried updating the platform-tools and it freezes here

Answer 1

Close android studio.
open a command window. 
type adb devices
no devices? 
trouble shoot connection and drivers and device developer option
see a device?
   type adb shell
   type ls -l
   type su
su not found? download or activate your superuser app
no problems with any step?
 open android studio and try again with it's terminal emulator