Dart: List of generic class that implements fromJson function - list

Question

I have an api which returns an entity of type Category which has the following implementation:
class Category {
final int id;
final String title;
Category({this.id, this.title});
factory Category.fromJson(Map<String, dynamic> json) =>
Category(id: json['id'], title: json['title']);
}
I am implementing fromJson function to map the result into an object of this class.
However, the result can contain some metadata and the actual result is incapsulated into a "content" field. The implementation would be something like this:
class CategoryWrapper {
List<Category> content;
int currentPage;
int totalItems;
int totalPages;
CategoryWrapper({this.content, this.currentPage, this.totalItems, this.totalPages});
factory CategoryWrapper.fromJson(Map<String, dynamic> json) {
var list = json['content'] as List;
List<Category> objectList = list.map((i) => Category.fromJson(i)).toList();
return CategoryWrapper(content: objectList, currentPage: json['currentPage'], totalItems: json['totalItems'], totalPages: json['totalPages']);
}
}
I am implementing the fromJson function here as well to map the results into an object of this class.
What I need is to have a generic class that can take any entity (for example Category) just like I can in Java. The class would look something similar to this:
class Wrapper<T> {
List<T> content;
int currentPage;
int totalItems;
int totalPages;
Wrapper({this.content, this.currentPage, this.totalItems, this.totalPages});
factory Wrapper.fromJson(Map<String, dynamic> json) {
var list = json['content'] as List;
List<T> objectList = list.map((i) => T.fromJson(i)).toList(); // this won't work
return Wrapper(content: objectList, currentPage: json['currentPage'], totalItems: json['totalItems'], totalPages: json['totalPages']);
}
}
But this won't work because I can't call the fromJson function from a generic type.
Is there a workaround for this I can use without complicating myself with two different classes for each entity?