Note: TWRP recovery and root(supersu o Magisk) is needed.
In our stock roms, face recognition is not available in smartlock. If you have a cutom rom with face reconition enable, skip step 1.
1a. Nougat: Flash open_gapps-arm64-7.1-nano-20180201_FACEUNLOCK4.ziphttps://drive.google.com/open?id=1zZ...N8DU8k6QhB8ODF
1b. Oreo 8.1 open_gapps-arm64-8.1-nano-20171215-UNOFFICIAL_FACEUNLOCK https://drive.google.com/open?id=1N-...4Wt-O1THUlG1Sc
1.c Oreo 8.0 FACE_UNLOCK_8.0.zip https://drive.google.com/open?id=1t6...PVO5ZtVLW-5IoB
2. In settings/security/trust agents, enable smart lock
3. In setting/security/smart lock Trusted face will be available. Configure your face.
4a:AEX 8.1 release newer than version of 10th February 2018: Enable settings/Extensions/Lockscreen/Locks creen UI/face auto unlock. All done! skip all the following steps.
4b:Nougat and Oreo 8.0. Install XposedInstaller_by_dvdandroid_31_10_17.apk.
5a. If you have supersu you need to install xposed with the Xposed installer just installed.
5b (my option). If you have magisk, you can install the magisk module Xposed Framework (SDK 25 for Android 7.1 and SDK 26 for Oreo 8.0) under in Magisk manager under Downloads menu.
6. Reboot. The reboot time is quite long...about 3 minutes...WAIT.
7. Now in app Xposed installer you would get the green status (Xposed framework active). (If you get the orange status you have to rebbot again. If you get red status, Xposed is not installed: try step 5 again)
8. In Xposed installer menu "Downloads", search InstantFaceUnlock. Enter, move to tab VERSIONS and push "Save" and the application IFU will be installed.
9. In Xposed installer menu "Modules", check "Instant Face Unlock"
11. Have fun!!!