我正在为考试做一个项目。我用Akka HTTP创建了一个服务器，并在Postman上试用了一下。一切正常。但是当我尝试使用Flutter发送请求时（顺便说一句，这是我第一次使用它），它给了我这个错误：
第一个月
下面我将我的服务器、我使用http请求的文件和info.plist文件留给您。

服务器端

import akka.http.scaladsl.model._
import akka.http.scaladsl.server.Directives._
import akka.http.scaladsl.server.Route
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._
import ch.megard.akka.http.cors.scaladsl.CorsDirectives.cors
import ch.megard.akka.http.cors.scaladsl.settings.CorsSettings
import akka.http.scaladsl.model.StatusCodes
import akka.http.scaladsl.server.ExceptionHandler

object Server {

  def customExceptionHandler: ExceptionHandler = ExceptionHandler {
    case exception: Exception => // Puoi specificare il tipo di eccezione che vuoi gestire
      extractUri { uri =>
        complete(StatusCodes.InternalServerError, s"Si è verificato un errore durante l'elaborazione della richiesta: ${exception.getMessage}")
      }
  }

  val corsSettings: CorsSettings = CorsSettings.defaultSettings.withAllowGenericHttpRequests(true)
  case class numUsersResponse(numUsers: Long)

  case class numFriendshipsResponse(numFriendships: Long)

  case class numAvgFriendsResponse(numAvgFriends: Double)
  case class FriendsListResponse(count: Long, friendsList: List[Long])

  case class CommonFriendsResponse(friends: List[Long])

  case class CountGroupsResponse(count: Long, groupIds: List[Long])

  case class GroupsUserResponse(userIds: List[Long])

  case class CommonGroupResponse(groupIds: List[Long])

  case class MostPopularGroupResponse(groupId: Long, userIds: List[Long])

  case class PopularNGroupsResponse(groupIds: List[Long])

  // Define JSON formats for the response case classes
  implicit val numUsersResponseFormat = jsonFormat1(numUsersResponse)
  implicit val numFriendshipsResponseFormat = jsonFormat1(numFriendshipsResponse)
  implicit val numAvgFriendsResponseFormat = jsonFormat1(numAvgFriendsResponse)
  implicit val friendsListResponseFormat = jsonFormat2(FriendsListResponse)
  implicit val commonFriendsResponseFormat = jsonFormat1(CommonFriendsResponse)
  implicit val countGroupsResponseFormat = jsonFormat2(CountGroupsResponse)
  implicit val groupsUserResponseFormat = jsonFormat1(GroupsUserResponse)
  implicit val commonGroupResponseFormat = jsonFormat1(CommonGroupResponse)
  implicit val mostPopularGroupResponseFormat = jsonFormat2(MostPopularGroupResponse)
  implicit val popularNGroupsResponseFormat = jsonFormat1(PopularNGroupsResponse)

  val numUser: Route =
    path("num_users") {
      get {
        cors() {
          complete(numUsersResponse(Queries.numUsers()))
        }
      }
    }

  val numFriendships: Route =
    path("num_friendships") {
      get {
        cors() {
          complete(numFriendshipsResponse(Queries.numFriendships()))
        }
      }
    }

  val most_popular: Route =
    path("most_popular") {
      cors() {
        get {
          parameters(Symbol("nUsers").as[Int]) { nUsers =>
            complete(Queries.most_popular(nUsers))
          }
        }
      }
    }

  val least_popular: Route =
    path("least_popular") {
      cors() {
        get {
          parameters(Symbol("nUsers").as[Int]) { nUsers =>
            complete(Queries.least_popular(nUsers))
          }
        }
      }
    }

  val friends_list: Route =
    path("friends_list") {
      cors() {
        get {
          parameters(Symbol("id").as[Long]) { id =>
            complete(Queries.friends_list(id))
          }
        }
      }
    }

  val commonFriends: Route =
    path("common_friends") {
      cors() {
        get {
          parameters(Symbol("id1").as[Long], Symbol("id2").as[Long]) { (id1, id2) =>
            complete(Queries.commonFriends(id1, id2))
          }
        }
      }
    }

  val countGroups: Route =
    path("count_groups") {
      cors() {
        get {
          parameters(Symbol("user_id").as[Int]) { id =>
            complete(Queries.countGroups(id))
          }
        }
      }
    }

  val groupsUser: Route =
    path("groups_user") {
      cors() {
        get {
          parameters(Symbol("id").as[Long]) { id =>
            complete(Queries.groupsUser(id))
          }
        }
      }
    }

  val commonGroup: Route =
    path("common_group") {
      cors() {
        get {
          parameters(Symbol("id1").as[Int], Symbol("id2").as[Int]) { (id1, id2) =>
            complete(Queries.commonGroup(id1, id2))
          }
        }
      }
    }

  val mostPopularGroup: Route =
    path("most_popular_group") {
      cors() {
        get {
          complete(Queries.mostPopularGroup())
        }
      }
    }

  val popularN_Group: Route =
    path("popularN_Groups") {
      cors() {
        get {
          parameters(Symbol("n").as[Int]) { n =>
            complete(Queries.popularN_Group(n))
          }
        }
      }
    }

  val friendAvg: Route =
    path("friends_avg") {
      get {
        cors() {
          complete(numAvgFriendsResponse(Queries.friendAvg()))
        }
      }
    }

  def route :Route= cors(corsSettings){
    concat(numUser,numFriendships, most_popular,least_popular, friends_list, commonFriends, countGroups, groupsUser, commonGroup,
      mostPopularGroup, popularN_Group,friendAvg )
  }


}

字符串

UserPage

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:friendster_project_frontend/pagine/home.dart';
import 'package:http/http.dart' as http;

//------------------------- SEZIONE QUERY E HTTP-------------------------------//

//numero utenti
/*
Future indica una chiamata futura che riceverà un stringa;
async indica che la chiamata è asincrona, quindi devo aspettare il risultato della chiamata http
*/
Future<int> getNumeroUtenti() async {
  var response = await http.get(Uri.parse('http://localhost:8080/friends_avg'));
  
  if (response.statusCode == 200) {
    // If the server returns a successful response, parse the JSON
    var data = json.decode(response.body);
    int numUsers = data['numUsers'];
    return numUsers;
  } else {
    // If the server did not return a successful response, throw an exception.
    throw Exception('Failed to load data');
  }
  
}

//-----------------------------------------------//

class UserPage extends StatefulWidget {
  const UserPage({super.key});

  @override
  State<UserPage> createState() => _UserPageState();

}

class _UserPageState extends State<UserPage>{

  //variabili che otteniamo con le chiamate http
  late Future<int> numeroUtenti;

  @override
  void initState(){
    super.initState();
    numeroUtenti = getNumeroUtenti(); //appena apro la pagina ottengo il numero di utenti
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      
      body: FutureBuilder(
       future: numeroUtenti,
       builder: (context,snapshot){
        if(snapshot.hasData){
           return Center(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  const Text('Numero utenti:'),
                  Text(
                    snapshot.data!.toString(),
                    style: const TextStyle(fontSize: 24, fontWeight: FontWeight.bold),
                  ),
                  ElevatedButton(
                    onPressed: () {
                      Navigator.push(context, MaterialPageRoute<void>(builder: (context) => const Home()));
                    },
                    child: const Text('Torna alla Home'),
                  ),
                ],
              ),
            );
        }
        else if(snapshot.hasError){
          return Center(child: Text("Erorre nella richiesta ${snapshot.error}") ,);
          
        }
        return const CircularProgressIndicator();
       },
      ),
    );
  }
}

型

info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>NSAppTransportSecurity</key>
    <dict>
        <key>NSAllowsArbitraryLoads</key>
        <true/>
    </dict>
    <key>com.apple.security.network.client</key>
    <true/>
    <key>CFBundleDevelopmentRegion</key>
    <string>$(DEVELOPMENT_LANGUAGE)</string>
    <key>CFBundleExecutable</key>
    <string>$(EXECUTABLE_NAME)</string>
    <key>CFBundleIconFile</key>
    <string></string>
    <key>CFBundleIdentifier</key>
    <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
    <key>CFBundleInfoDictionaryVersion</key>
    <string>6.0</string>
    <key>CFBundleName</key>
    <string>$(PRODUCT_NAME)</string>
    <key>CFBundlePackageType</key>
    <string>APPL</string>
    <key>CFBundleShortVersionString</key>
    <string>$(FLUTTER_BUILD_NAME)</string>
    <key>CFBundleVersion</key>
    <string>$(FLUTTER_BUILD_NUMBER)</string>
    <key>LSMinimumSystemVersion</key>
    <string>$(MACOSX_DEPLOYMENT_TARGET)</string>
    <key>NSHumanReadableCopyright</key>
    <string>$(PRODUCT_COPYRIGHT)</string>
    <key>NSMainNibFile</key>
    <string>MainMenu</string>
    <key>NSPrincipalClass</key>
    <string>NSApplication</string>
</dict>
</plist>

型
我用的是VS代码
我以为加上

<key>NSAppTransportSecurity</key>
    <dict>
        <key>NSAllowsArbitraryLoads</key>
        <true/>
    </dict>
<key>com.apple.security.network.client</key>
    <true/>

型
因为每个人都说我只需要添加这行代码。