List<Object> conversion from netcore server api in Flutter Dart - flutter

Question

I am trying to convert a list of objects(List<Object> in Flutter) to a defined type(class) in a flutter project. I have tried examples on converting the list as shown in Serializing Your Object in Flutter . Every time I get Map<String, dynamic> is not a subtype of List<dynamic>. But tried something different, same error. Posted is the sample code for the latter not from Serializing Your Object in Flutter. Is there an alternative to achieving this? Really appreciate your responses. [Updated]
Custom Object
#JsonSerializable(explicitToJson: true)
class Activity{
String id;
String name;
double amount;
Activity({ this.amount, this.name , this.id});
Activity.fromJson(Map<String, dynamic> json){
id = json["id"];
name = json["name"];
amount = json["amount"];
}
Map<String, dynamic> toJson() => {
'id' : id,
'name' : name,
'amount' : amount,
};
}
Sample Flutter Screen
initiateConnection(){
var builder = HubConnectionBuilder();
this._hubConnection = builder.withUrl("##########################").build();
_hubConnection.onclose( (error) => print("Connection Closed"));
this._hubConnection.on("Activities", formActivityDashboard );
this._hubConnection.start().then((data) => print("Connected"));
}
formActivityDashboard(List<Object> data){
final items = (data).map((i) => new Activity.fromJson(i));
for (final item in items) {
print(item.id);
}
}

Answer 1

List<dynamic>ActivityList=json.decode(response.body);
List<Activity> myActivityList = new List();
for(int i=0;i<ActivityList.length;i++)
{
Map<String, dynamic>ActivityData = ActivityList.elementAt(i);
Activity act=new Activity();
act.id=ActivityData['id']
act.name=ActivityData['name']
act.amount=ActivityData['amount']
myActivityList.add(act);
}