Keyguard doesn't get locked after pressing back button when isn't secured with a password on at least API 29

[user98392]

After the LockScreenActivity is launched over the lockscreen and there's no password configured when pressing back button you will go back to the MainActivity instead of the lockscreen.

The fix is to add attributes android:showWhenLocked(true) and android:turnScreenOn(true) to the LockScreenActivity tag in the manifest. The code in the LockScreenActivity class and the attribute android:showOnLockScreen are useless (at least on Android 10). Fix it by yourself, I'm just too lazy to create a PR.