我有两个组成部分：ping和pong，Ping应该通过服务向pong发送消息。通过使用Rxjs，尽管我正在使用官方文档示例，但我似乎没有发送或接收任何内容。 这是服务和两个组件的代码：

服务文件：

import { Injectable } from '@angular/core';
import { Subject,Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class MessagingServiceService {
  private _message : Subject<string>  = new Subject<string>();
  message$ : Observable<string>;
  constructor() { 
    this.message$ = this._message.asObservable();
  }

  sendMessage(message: string)
  {
    console.log(this.message$);
    this._message.next(message);
  }
}

Ping组件：

import { Component,OnInit } from '@angular/core';
import { MessagingServiceService } from '../messaging-service.service';

@Component({
  selector: 'app-ping',templateUrl: './ping.component.html',styleUrls: ['./ping.component.css']
})
export class PingComponent implements OnInit {

  message :string = "";
  constructor(private messageService : MessagingServiceService) { }

  ngOnInit() {
  }

  sendMessage()
  {
    console.log(this.message);
    this.messageService.sendMessage(this.message);
  }

}

乒乓组件：

import { Component,OnInit } from '@angular/core';
import { MessagingServiceService } from '../messaging-service.service';


@Component({
  selector: 'app-pong',templateUrl: './pong.component.html',styleUrls: ['./pong.component.css']
})
export class PongComponent implements OnInit {

  recivedMessage :string ="";
  constructor(private messagingService: MessagingServiceService) {
    this.reciveMessages();
    this.messagingService.message$.subscribe(res=>{
      console.log(res);
      this.recivedMessage = res;
    })

   }

  ngOnInit() {
  }

  reciveMessages()
  {
    this.messagingService.message$.subscribe(res=>{
      console.log(res);
      this.recivedMessage = res;
    })
  }

}