Dart APIunself_componentUnRootSheetPagemaintainState maintainState property Null safety bool maintainState final Implementation final bool maintainState; unself_component unself_component UnRootSheetPage<T> maintainState property UnRootSheetPage class Constructors UnRootSheetPage Properties arguments child fullscreenDialog hashCode key maintainState name restorationId runtimeType Methods canUpdate createRoute noSuchMethod toString Operators operator ==