Dart APIunself_componentUnselfSliverNavigationBarstretch stretch property Null safety bool stretch final Implementation final bool stretch; unself_component unself_component UnselfSliverNavigationBar stretch property UnselfSliverNavigationBar class Constructors UnselfSliverNavigationBar Properties automaticallyImplyLeading automaticallyImplyTitle backgroundColor border brightness hashCode heroTag key largeTitle leading middle opaque padding previousPageTitle runtimeType stretch trailing transitionBetweenRoutes Methods createElement createState debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==