Dart APIunself_componentUnSliverAppBartrailing trailing property Null safety Widget? trailing final Implementation final Widget? trailing; unself_component unself_component UnSliverAppBar trailing property UnSliverAppBar class Constructors UnSliverAppBar Properties description emoji hashCode implyLeading isCollapseCentered isImmersive key leading runtimeType title trailing Methods createElement createState debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==