Difference between R.layout and android.R.layout

Question

What is the difference between

   setContentView(R.layout.main);

and

ArrayAdapter arrayAdapter = new ArrayAdapter(this,
            


        

Answer 1

android.R.

is used for access predefined classes by android SDK (layouts/drawables)

R

is used for access custom classes(that means its layouts/drawables imported/created by user)