Dart APIunself_componentUnSliverArtBarleading leading property Null safety Widget? leading final Implementation final Widget? leading; unself_component unself_component UnSliverArtBar leading property UnSliverArtBar class Constructors UnSliverArtBar Properties action background description emoji hashCode isImmersive key leading name runtimeType trailing Methods createElement createState debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==