This is a sample Android application that shows how to make the Toolbar widget to hide/show when scrolling content. It follows the same pattern as Android Google Play Music application.
Here is a video of Android Google Play Music app depicting it's Toolbar behavior:
Here is a video of the sample app in action:
You can read more about it on my blog.
Android, Toolbar, Lollipop, Material Design
If you find this code useful buy Randy Saborio a beer.