javascript - SignalR Javascript 客户端回调未被触发

Question

我能够连接到我的集线器，并且我已连接 OnConnected 和 OnDisconnected。他们应该对整数进行加/减，并使用新值调用客户端回调。我的 Angular 应用程序成功连接到服务器，但我注册的回调函数没有被触发。

这是我的服务器中心:

[HubName("online")]
public class OnlineHub : Hub
{
    private static int userCount = 0;

    public override Task OnConnected()
    {
        userCount++;
        Clients.All.listUpdated(userCount);

        return base.OnConnected();
    }

    public override Task OnDisconnected(bool stopCalled)
    {

        userCount--;

        Clients.All.listUpdated(userCount);

        return base.OnDisconnected(stopCalled);
    }
}

这是我的 Angular SignalRService:

import { AppSettings } from './../app.settings';
import { EventEmitter, Injectable, OnDestroy } from '@angular/core';

declare const $: any;

@Injectable()
export class SignalRService {

  // Declare the variables
  private onlineHub: any;
  // create the Event Emitter
  public messageReceived: EventEmitter<any>;
  public connectionEstablished: EventEmitter<Boolean>;
  public connectionExists: Boolean;

  constructor(private appSettings: AppSettings) {
    // Setup
    this.connectionEstablished = new EventEmitter<Boolean>();
    this.messageReceived = new EventEmitter<any>();
    this.connectionExists = false;
  }

  // This method gets executed from angular controller
  public initialize(proxyName: string): void {
    this.onlineHub = $.connection.online;

    this.onlineHub.client.listUpdated = function(list: any): void {
      console.log(list);
      this.messageReceived.emit(list);
    };

    this.startConnection();
  }

  private startConnection(): void {
    $.connection.hub.url = this.appSettings.SIGNALR_BASE_URL + '/signalr';
    $.connection.hub.start()
      .done((data: any) => {
        console.log('SignalR Connected with: ' + data.transport.name);
        this.connectionEstablished.emit(true);
        this.connectionExists = true;
      })
      .fail((error: any) => {
        console.log('SignalR could not connect: ' + error);
        this.connectionEstablished.emit(false);
      });
  }

  private registerOnServerEvents() {
    this.onlineHub.client.listUpdated = function(list: any): void {
      console.log(list);
      this.messageReceived.emit(list);
    };
  }
}

按照文档所述，我在运行 start() 之前注册回调“listUpdated”，并且 $.connection.hub 在调用 start() 之前包含 client.listUpdated，因此它应该注册。但 OnConnected 方法仍然没有被调用。

Answer 1

我通过将 OnConnected() 和 OnDisconnected() 代码包含在 try/catch block 中解决了这个问题，并创建了一个名为“error”的客户端方法，该方法将最终的异常返回给客户端。这样我发现我遇到了 Json 序列化问题。

我的中心现在看起来像这样:

    [HubName("online")]
    public class OnlineHub : Hub
    {
        private static int userCount = 0;


        public override Task OnConnected()
        {
            try
            {
                userCount++;
                Clients.All.listUpdated(userCount);

            }
            catch (Exception exc)
            {
                Clients.All.error(exc);
            }

            return base.OnConnected();
        }

        public override Task OnDisconnected(bool stopCalled)
        {
            try
            {
                userCount--;
                Clients.All.listUpdated(userCount);
            }
            catch (Exception exc)
            {
                Clients.All.error(exc);
            }

            return base.OnDisconnected(stopCalled);
        }
    }

并且我在调用 start() 之前在 js 客户端上注册错误回调:

this.onlineHub.client.error = (exc: any): void => {
  console.log('Error occured:', exc);
};