question: View createSectionHeaderIfNeeded ( RecyclerView . Recycler recycler , int sectionIndex ) { if ( adapter . doesSectionHaveHeader ( sectionIndex ) ) { for ( int i = 0 , n = getChildCount ( ) ; i < n ; i ++ ) { View view = getChildAt ( i ) ; if ( getViewBaseType ( view ) == SectioningAdapter . TYPE_HEADER && getViewSectionIndex ( view ) == sectionIndex ) { return view ; } } int headerAdapterPosition = adapter . getAdapterPositionForSectionHeader ( sectionIndex ) ; View headerView = recycler . getViewForPosition ( headerAdapterPosition ) ; headerViews . add ( headerView ) ; addView ( headerView ) ; measureChildWithMargins ( headerView , 0 , 0 ) ; return headerView ; } return null ; }
target:  Get the header item for a given section, creating it if it's not already in the view hierarchy