HTTP Get Json and Cast To Dart Map - android-studio

Question

I've started to learn Dart, but I stuck.
I follow this tutorial but something goes wrong.
Here is the problem: I would like to reach out to an API and fetch data from it. Nice!
I've imported packages for doing requests and converting. API returns the data correctly. HTTP GET is working.
The troubles came when I tried to assign json.decode(response.body) to Map().
It always says: The argument type dynamic cannot be assigned to the parameter type Map<String, dynamic>.
Could someone explain why that it's happening and how to handle it?
I'm using Android Studio. I'm invoking the function in the StatefulWidget:
var trends = fetchData('getAll', params);
where params is a Map().
The code:
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;
Future<ApiResponse> fetchData(String command, Map params) async {
final String url =
'https://example.com/api/v2/....';
final response = await http.get(url);
if (response.statusCode == 200) {
return ApiResponse.fromJson(json.decode(response.body));
} else {
// If that call was not successful, throw an error.
throw Exception('Failed to load post');
}
}
}
class ApiResponse{
final String result;
final String error;
final String error_number;
final String response_code;
PopnableResponse(
{this.result, this.error, this.error_number, this.response_code});
factory ApiResponse.fromJson(Map<String, dynamic> json) {
return ApiResponse(
result: json['result'] as String,
error: json['error'] as String,
error_number: json['error_number'] as String,
response_code: json['response_code'] as String,
);
}
}
JSON Example:
{
"error":"",
"error_number":"",
"response_code":200,
"result":[
{
"id":1,
"name":"Great Deal",
"day_aired":"2015-07-05 11:06:09",
"trend":"Noone"
},
{
"id":2,
....
}
]
}

Answer 1

Try to cast it
json.decode(response.body) as Map<String, dynamic>