flutter - Yandex 导航键

Question

有人可以帮助我对 dart yandex 导航键进行相同的说明。我有 .pem 密钥，如何使用密钥签署我的网址。

这是主要代码

import 'package:encrypt/encrypt.dart';
import 'package:crypto/crypto.dart';
import 'dart:convert' ;

void main () async {

String initUrl = 'yandexnavi://build_route_on_map?lat_to=$lat_to&lon_to=$lon_to&client=$client';

var bytes = utf8.encode(initUrl);
Digest sha256Result = sha256.convert(bytes);

var fileString = await rootBundle.loadString('resources/private_key.pem');

final parser = RSAKeyParser();

dynamic privateKey = parser.parse(fileString);

final signer = Signer(RSASigner(RSASignDigest.SHA256, privateKey: privateKey ));

var signature = signer.sign(base64.encode(bytes)).base64;

var  ynaviUrl = 'yandexnavi://build_route_on_map?lat_to=$lat_to&lon_to=$lon_to&client=$client&signature=$signature';

}