New to android need to understand “?android:attr/actionBarSize”

Question

I was going through Lars Vogel\'s tutorial on using Fragments and I came across the following code:

android:layout_marginTop=\"?android:attr/actionBarSize\"
         


        

Answer 1

While building android apps, one requires to know the properties of the Android client. Such as screen size etc. One such method is by using android:attr which is android attributes. Here you have mentioned to return a specific attribute by mentioning the keyword after / symbol. Here the keyword is actionBarSize.

The ? symbol is an operator which is used to access system configurations and properties in Android