Please, rate it on Google Play..
Lock the screen of your Android device simply clicking on the Zzz app icon.
Fully compatible with Android 7.x
This action will preserve your hardware button!
After locking, your device will go to sleep, preseving the battery too!
This app uses the Device Administrator permission.
Unlike many other apps in the market, this app doesn't read your personal data.
Verify yourself: NO PERSONAL DATA PERMISSIONS ARE REQUIRED FROM THIS APP :-)
This is not a widget, simply the smallest application in the Android market. No memory will be used during normal device operations.
Works on Android version 2.2 or above, (verified also on Android 6 and 7)!
Prior to uninstall this app, go to SETTINGS => LOCATION AND SECURITY => DEVICE ADMINISTRATION and deselect the device admin (Zzz in this case) which you want to uninstall.
Next, uninstall the application, you should be able to do it.