What is `abc` prefix on R.dimen fields?

Question

I wonder what is the meaning of abc prefix on R.dimen fields.

https://developer.android.com/reference/android/support/v7/appcompat/R.dimen.html

Can I use those values in my layout.xml or somewhere?

Answer 1

It is a prefix used by AppCompat to minimize naming conflicts with your code and other libraries. It is an abbreviation of ActionBarCompat.

You can find the commit that initially added this prefix to AppCompat here.