NiLS uses a floating overlay window to display notifications, therefore it is capable for displaying that content over non-stock lock screen apps such as WidgetLocker, C-Locker and many more.
However, not all of the lock screen apps are supported - some lock screen apps uses the same technique NiLS uses to display themselves so NiLS cannot be displayed on top of them.
To make NiLS appear on your lock screen app you should perform the following steps:
- Go to NiLS main settings page and enable "NiLS Auto Hide Service". this is an optional step but in many cases (especially on Android Lollipop or later) it is the only way to help NiLS detect the currently running lock screen app.
- Go to NiLS > Lock screen and enable "Auto Detect Lock Screen" option.
- Turn off your screen. wait few seconds (so your lock screen can be activated).
- Turn on your screen. you should get a popup dialog: "lock screen app detected" with the name of your lock screen app. click "Yes" on that dialog to save the detected lock screen app.
- NiLS notifications list should appear instantly.
- Go to NiLS > Lock screen and make sure your lock screen app appears correctly under "Auto detect lock screen" option.
- Disable "Auto detect lock screen" option so those popups won't appear again.
- Turn off your screen, then turn it on again to see if NiLS is working properly.
If you can't get NiLS to disappear after unlocking the device, the only workaround is to enable "Hide on outside tap" option under NiLS > Lock screen so NiLS will be hidden after a tap on the lock screen, no matter if you unlocked it or not.