问behaviorSubject next()不工作角8

EN

import { Injectable } from '@angular/core';
import { BehaviorSubject } from 'rxjs';
@Injectable({
  providedIn: 'root'
})
export class HeaderService {
  showSearch = new BehaviorSubject<boolean>(true);
  public showSearchObservable = this.showSearch.asObservable()
  constructor(){}
}

import { Component, OnInit } from '@angular/core';
import { HeaderService } from './header.service';
@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.scss']
})
export class HeaderComponent implements OnInit {
  searchShow;
  constructor(
    private headerService: HeaderService
  ) {}

  ngOnInit() {
    this.headerService.showSearchObservable.subscribe(
      value => {
        this.searchShow = value
        console.log(value) ##==> prints true first time when header is initialized but does not prints anything when search component is loaded
      }
    )
  }
}

import { Component, OnInit } from '@angular/core';
import { HeaderService } from 'src/app/shared/header/header.service.js';
@Component({
  selector: 'app-search',
  templateUrl: './search.component.html',
  styleUrls: ['./search.component.scss']
})
export class SearchComponent implements OnInit {
 constructor(
    private headerService: HeaderService
  ) {}

  ngOnInit() {
    console.log(this.headerService.showSearch.value) ##==> prints true
    this.headerService.showSearch.next(false)
    console.log(this.headerService.showSearch.value) ##==> prints false, but this value is not emitted to header component
}
}