question: public Header onGetInitialHeader ( ) { for ( int i = 0 ; i < mHeaders . size ( ) ; i ++ ) { Header h = mHeaders . get ( i ) ; if ( h . fragment != null ) { return h ; } } throw new IllegalStateException ( "Must have at least one header with a fragment" ) ; }
target:  Called to determine the initial header to be shown.  The default implementation simply returns the fragment of the first header.  Note that the returned Header object does not actually need to exist in your header list -- whatever its fragment is will simply be used to show for the initial UI.