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