Dart APIunself_componentUnSliverAppBarisCollapseCentered isCollapseCentered property Null safety bool isCollapseCentered final Implementation final bool isCollapseCentered; unself_component unself_component UnSliverAppBar isCollapseCentered 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 ==