On the other hand, many users have noticed that your Galaxy S4, after upgrading to Android 4.4.2 KitKat unexpectedly shuts down. Once black screen, users can unlock it again without any problems, but this error is quite annoying when you are working with the mobile screen.
The solution to this error is very simple, just go to "Settings" and then the functions of "Screen lock". Within the option of "Lock screen widgets", choose "Personal Message" or "Clock" and then select "Clock". This problem of the black screen fix.