如何在angular 8中根据上一页设置页面标题

import { Injectable } from '@angular/core';
import { Title } from '@angular/platform-browser';

@Injectable({
  providedIn: 'root'
})
export class TitleService {
  private defaultTitle = '默认标题';

  constructor(private title: Title) { }

  setTitle(newTitle: string) {
    this.title.setTitle(newTitle);
  }

  setDefaultTitle() {
    this.title.setTitle(this.defaultTitle);
  }
}

import { Component, OnInit } from '@angular/core';
import { TitleService } from '路径/到/TitleService';

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

  constructor(private titleService: TitleService) { }

  ngOnInit() {
    // 在ngOnInit生命周期钩子中设置页面标题
    this.titleService.setTitle('你的页面标题');
  }

}

import { Component, OnInit } from '@angular/core';
import { Router, NavigationEnd } from '@angular/router';
import { filter } from 'rxjs/operators';
import { TitleService } from '路径/到/TitleService';

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

  constructor(private router: Router, private titleService: TitleService) { }

  ngOnInit() {
    this.router.events
      .pipe(filter(event => event instanceof NavigationEnd))
      .subscribe((event: NavigationEnd) => {
        // 根据上一页的路由路径设置页面标题
        if (event.url === '/your-previous-page') {
          this.titleService.setTitle('上一页的页面标题');
        }
      });
  }

}