Lock Screen is a free android app that locks your screen (this is NOT a widget).
This app requires Device Administration to lock the screen,
and Device Administration needs to be disabled before uninstall.
This app works best with PIN unlock or Pattern unlock,
if you use Fingerprint unlock then you will still need to enter your PIN or Pattern after locking with Lock Screen,
this is a "feature" of android's Device Administration.
ShiraleeApps Lock Screen Privacy Policy:
NO data is collected from this app.
NO data is transmitted anywhere from this app.
NO statistics are generated\transmitted\stored anywhere.
You can't get much more private than that!