When the user clicks anywhere on the screen, I want the Actionbar to hide and when pressed again it should reappear.
I know there is something called actionbar.hide(); and show, but can you please help me how to implement it? :)
Just hide():
getActionBar().hide();
when you want to hide it, and use show():
getActionBar().show()
when you want to show it. That's about it.
Remember that if you're using View.SYSTEM_UI_FLAG_FULLSCREEN, this will not work properly.