SliverPersistentHeader constructor

const SliverPersistentHeader({Key key, @required SliverPersistentHeaderDelegate delegate, bool pinned: false, bool floating: false })

Creates a sliver that varies its size when it is scrolled to the start of a viewport.

The delegate, pinned, and floating arguments must not be null.

Implementation 

const SliverPersistentHeader({
  Key key,
  @required this.delegate,
  this.pinned = false,
  this.floating = false,
}) : assert(delegate != null),
     assert(pinned != null),
     assert(floating != null),
     super(key: key);