我正在尝试使用命名路线导航到另一个页面：
... RaisedButton(
child: Text('Get image'),
onPressed: () => Navigator.pushNamed<String>(
context, '/second'),...
但是得到错误
> I/flutter (12439): ??? EXCEPTION CAUGHT BY GESTURE
> ????????????????????????????????????????????????????????????????????
> I/flutter (12439): The following assertion was thrown while handling a gesture:
> I/flutter (12439): type 'MaterialPageRoute<dynamic>' is not a subtype of type 'Route<String>'
> I/flutter (12439): Either the assertion indicates an error in the framework itself, or we should provide substantially
> I/flutter (12439): more information in this error message to help you determine and fix …flutter ×1