How to add value from Json into a list object using Flutter?

I have a class User and a List like this:

List<User> users = List();

class User {
  int id;
  String name;

  User({this.id, this.name});

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json["id"] as int,
      name: json["name"] as String
    );
  }
}

and a Json Data like below:

  var DataUser= [
    {"id": 1, "name": "Leanne"},
    {"id": 2, "name": "Graham"}
  ];

How can I add value from DataUser into List<User> users?

You can iterate through the List of json objects and use your User.fromJson to convert each json object to a User object.

I added a demo using your code as an example:

List<User> users = List();

  var DataUser = [
    {"id": 1, "name": "Leanne"},
    {"id": 2, "name": "Graham"}
  ];

  List<User> getUsersFromJson() {
    // iterate through the list of json
    for (var json in DataUser) 
    // add the user object to your list
    users.add(User.fromJson(json));
    // return the list of users
    return users;
  }