Dart APIsettings_listSettingsListSliveronSelectLicense onSelectLicense property Null safety VoidCallback onSelectLicense final Implementation final VoidCallback onSelectLicense; unself_settings_list settings_list SettingsListSliver onSelectLicense 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 ==