Dart APIunself_componentUnselfSliverNavigationBarbackgroundColor backgroundColor property Null safety Color? backgroundColor final Implementation final Color? backgroundColor; unself_component unself_component UnselfSliverNavigationBar backgroundColor 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 ==