问题
In recent android L apps ( lets say google i/o 2014 app) with material theme we have seen that if there is image view at top (followed by any kind of list), then to begin with the actionbar is transparent, then as the user scrolls down the actionbar gradually becomes solid color.
2 questions: 1. does this phenomenon have some name, if yes what is it? 2. how do i code to achieve this in an app for android L or is it default
回答1:
take a look here : https://github.com/ManuelPeinado/FadingActionBar
second question : based on my researching until now, we have to implement it by code. it's called Fading action bar. You should install Libraries for developers (Android application) that have a lot of libraries demo.
来源：https://stackoverflow.com/questions/25469439/how-to-gradually-turn-transparent-action-bar-into-solid-color-as-user-scrolls-do