Cast Error during HTTP Post Request to Google Route API, - flutter

Question

This is the first time I am trying to use an HTTP Rest API with Post request, I am trying to use google Route API to compute direction, I follow the body from the google documentation however I keep getting this error
_CastError
Exception has occurred.
_CastError (type '_Map<String, Map<String, Map<String, double>>>' is not a subtype of type 'String' in type cast)
This is the first time I am trying a post request so I have no idea what is wrong
here' the code I use
import 'dart:async';
import 'dart:ffi';
import 'package:http/http.dart' as http;
import 'package:flutter/material.dart';
import 'package:flutter_polyline_points/flutter_polyline_points.dart';
import 'dart:convert' as convert;
class RouteAPI {
final String key = 'API_KEY_HERE';
Future<Void> getRoute() async {
final String Url =
'https://routes.googleapis.com/directions/v2:computeRoutes?KEY=$key';
var response = await http.post(Uri.parse(Url), body: {
"origin": {
"location": {
"latLng": {
"latitude": -6.2425120808113315,
"longitude": 106.85152720596324
}
},
},
"destination": {
"location": {
"latLng": {
"latitude": -6.2425120808113315,
"longitude": 106.85152720596324
}
},
},
"intermediates": {
"location": {
"latLng": {
"latitude": -6.178359098658539,
"longitude": 106.79219133887105
}
},
},
"travelMode": "DRIVE",
"routingPreference": "TRAFFIC_AWARE",
"polylineQuality": "HIGH_QUALITY",
"polylineEncoding": "ENCODED_POLYLINE",
//"departureTime": "",
"computeAlternativeRoutes": "FALSE",
"routeModifiers": {
"avoidTolls": false,
"avoidHighways": false,
"avoidFerries": false
},
"languageCode": "en-US",
"units": "IMPERIAL"
});
var json = convert.jsonDecode(response.body);
print(json.toString());
return json;
}
}
I tried to send a post body to request an encoded polyline from google route API

Answer 1

Don't include API keys directly in your project, use environment variables, once someone has your API key, this can end bad with a lot of debt. Make sure you reset your key.
flutter_dotenv.
You also need to include your API key in your request header, from what I read. Compute a route docs
You're receiving a type error because you're not encoding your body JSON into a string.
convert.jsonEncode({"example": "example"})
You then aren't setting the content type header to let the API know what kind of data you're sending, and the API Key, along with the field mask header.
headers: {
"Content-Type": "application/json",
"X-Goog-Api-Key": "API_KEY",
"X-Goog-FieldMask": "routes.duration,routes.distanceMeters,routes.polyline.encodedPolyline"};
I've replaced your response section for you.
var response = await http.post(Uri.parse(url),
body: convert.jsonEncode({
"origin": {
"location": {
"latLng": {
"latitude": -6.2425120808113315,
"longitude": 106.85152720596324
}
},
},
"destination": {
"location": {
"latLng": {
"latitude": -6.2425120808113315,
"longitude": 106.85152720596324
}
},
},
"intermediates": {
"location": {
"latLng": {
"latitude": -6.178359098658539,
"longitude": 106.79219133887105
}
},
},
"travelMode": "DRIVE",
"routingPreference": "TRAFFIC_AWARE",
"polylineQuality": "HIGH_QUALITY",
"polylineEncoding": "ENCODED_POLYLINE",
//"departureTime": "",
"computeAlternativeRoutes": "FALSE",
"routeModifiers": {
"avoidTolls": false,
"avoidHighways": false,
"avoidFerries": false
},
"languageCode": "en-US",
"units": "IMPERIAL"
}),
headers: {
"Content-Type": "application/json",
"X-Goog-Api-Key": "API_KEY",
"X-Goog-FieldMask": "routes.duration,routes.distanceMeters,routes.polyline.encodedPolyline"
});