Dart APIsettings_dataSettingsDataSliveronReset onReset property Null safety VoidCallback? onReset final Implementation final VoidCallback? onReset; unself_settings_data settings_data SettingsDataSliver onReset property SettingsDataSliver class Constructors SettingsDataSliver Properties hashCode key onReset runtimeType Methods build createElement debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator == Static methods children