Yes you are correct,i didn't restore the screenBrightness back.
I am not clear about when to restore it.

Lets consider the below case:
If the Lowbattery case reduced the brightness level to 0.5.After that user changes the brightness level,if i restore with the old value,then its wrong.
We don't have brightness listener to listen always.

If you have any idea about this please let me know.