React Native中未调用SignalR侦听器

Question

我正在React Native中为.NET编写的后端构建一个移动应用程序。后端已使用SignalR集线器实现了实时消息传递服务。我正在使用软件包react-native-signalr。连接已建立，我可以通过调用proxy.invoke将消息发送到SignalR集线器。问题在于接收消息。我尝试使用proxy.on，但没有任何反应。

componentDidMount(){
  const { access_token } = this.props;

  // Setup connection to signalr hub.
  const hubUrl = `${API_URL}/signalr`;
  const connection = signalr.hubConnection(hubUrl);
  const proxy = connection.createHubProxy('MessagesHub', {queryParams: { token: access_token }});

  // Start connection
  connection.start();

  // Trying to receive message from SignalR Hub
  proxy.on('messageReceived', message => {
    console.log(message);
  })
  proxy.on('sendPrivateMessage', message => {
    console.log(message);
  })
  proxy.on('sentPrivateMessage', message => {
    console.log(message);
  })
}

Answer 1

当您使用your_proxy.on函数注册一个侦听器时，必须定义一个具有必需参数的函数，并将其绑定到构造函数上，然后将其传递给your_proxy.on函数，请参见下面的对话框：

constructor(props){
        super(props);
        this.messageReceived=this.messageReceived.bind(this);   // <========== **Important**
        this.sendPrivateMessage=this.sendPrivateMessage.bind(this);   // <========== **Important**
        this.sentPrivateMessage=this.sentPrivateMessage.bind(this);   // <========== **Important**
    }

messageReceived(message ){
             console.log(message);
    }
    sendPrivateMessage(message ){
             console.log(message);
    }
    sentPrivateMessage(message ){
             console.log(message);
    }
componentDidMount(){
  const { access_token } = this.props;

  // Setup connection to signalr hub.
  const hubUrl = `${API_URL}/signalr`;
  const connection = signalr.hubConnection(hubUrl);
  const proxy = connection.createHubProxy('MessagesHub', {queryParams: { token: access_token }});

// Trying to receive message from SignalR Hub
  proxy.on('messageReceived', this.messageReceived);
  proxy.on('sendPrivateMessage', this.sendPrivateMessage);
  proxy.on('sentPrivateMessage', this.sentPrivateMessage);

  // Start connection
  connection.start();
}