Dart APIsettings_listSettingsListSliveronSelectAppearance onSelectAppearance property Null safety VoidCallback onSelectAppearance final Implementation final VoidCallback onSelectAppearance; unself_settings_list settings_list SettingsListSliver onSelectAppearance property SettingsListSliver class Constructors SettingsListSliver Properties children hashCode key onSelectAppearance onSelectData onSelectFeedback onSelectLicense onSelectPrivacy onSelectTerms runtimeType Methods build createElement debugDescribeChildren debugFillProperties noSuchMethod toDiagnosticsNode toString toStringDeep toStringShallow toStringShort Operators operator ==