Hide top bar when scrolling down

Question

how can I obtain same or similar result to top bar in Google Keep app (Android) - which is always on and if we scroll down its hides. Similar is done in Chrome browser on Android.

It appear again when scrolling up.

Valid XHTML http://img542.imageshack.us/img542/5980/unnamedap.jpg

Answer 1

Here is a 3rd party library that does that called QuickReturn Listview

Answer 2

Pretty awesome library for it here. http://www.androidviews.net/2012/12/quickreturn-listview/