OkHttp – keep getting the error: "content-type of request should be application/json"

Why do I get this error "content-type of request should be application/json", because I encoded it application/json?
How to correct it?
In Postman the request is working fine.

int id = 208;
MediaType JsonType = MediaType.parse("application/json");
OkHttpClient client = new OkHttpClient();
String jsonBody = "{\"params\":[\"wandelnet\"," + id + "]}";
RequestBody body = RequestBody.create(jsonBody, JsonType);
Request request = new Request.Builder()
        .url( "https://wandelnet.api.routemaker.nl/routemaker/getPublishedRoute")
        .post(body)
        .addHeader("Content-Type", "application/json; charset=utf-8")
        .addHeader( "Accept", "application/json")
        .build();
Response response = client.newCall(request).execute();

The result is:

{"result":null,"error":{"code":"sherpaBadRequest","message":"content-type
of request should be application/json"}}

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>Solution :

Try creating the request body from bytes, not from a string:

RequestBody body = RequestBody.create(jsonBody.getBytes(“UTF-8”), JsonType);

OkHttp automatically adds a charset when it does string encoding, and we need to prevent this here.

You’ll also want to omit the Content-Type header in your request builder.