Angular服务中重定向后无法获取初始路由数据的问题

我在基于当前路由创建动态面包屑数据时遇到问题：Angular服务中无法获取重定向后的首个路由数据，仅将代码移至组件内时才能正常获取。

相关代码 #

路由配置（app.routing） #

export const routes: Route[] = [
  {
    path: '',
    canActivate: [AuthGuard],
    component: LayoutMainComponent,
    children: [
        {
        path: 'first',
        children: [
          {
            path: 'second',
            loadComponent: () =>
              import('....component'),
          },
          {
            path: '',
            redirectTo: 'first',
            pathMatch: 'prefix',
          },
        ],
      },

      {
        path: '',
        redirectTo: 'first/second',
        pathMatch: 'prefix',
      },
]

面包屑服务代码 #

当前的Observable在用户切换路由时正常工作，但首次加载时无法获取重定向后的路由：

// 该Observable在用户切换路由时正常工作，但首次加载时无效
breadcrumbMenuItems$: Observable<MenuItem[]> = this.router.events.pipe(
  filter((event): event is NavigationEnd => event instanceof NavigationEnd),
  map((event: NavigationEnd) => {
    const url = event.urlAfterRedirects || this.router.url;
    return this.generateBreadcrumbs(url);
  }),
  startWith(this._fetchInitialBreadcrumbs()),
  distinctUntilChanged(),
  catchError((error: any) => {
    console.error(this.errorMessage, error);
    return of([]);
  }),
);

尝试获取重定向路由的代码 #

我尝试了多种方式获取目标路由/first/second，但结果要么是重定向前的空路径/，要么是undefined：

constructor(
  private router: Router,
  private activatedRoute: ActivatedRoute,
  private readonly location: Location
) {
  console.log('========= ROUTER ===========');
  console.log('ROUTER::', this.router);
  console.log( 'ROUTER: routerState.snapshot-URL:',
    this.router.routerState.snapshot.url );
  console.log('this.router.url:', this.router.url);

  console.log(' =============== ACTIVATED ROUTE ===============');
  console.log('activatedRoute.pathFromRoot:',
    this.activatedRoute.pathFromRoot );
  console.log( 'activatedRoute.snapshot.url:',
    this.activatedRoute.snapshot );

  this.activatedRoute.paramMap.subscribe((params) => {
    console.log(
      'params:', params );

   console.log( 'params.next:', params['next'] );
  });

  console.log( 'routeConfig',
    this.activatedRoute.routeConfig?.path?.split('?')[0] );

  console.log(' ========== Angular LOCATION ===========');
  console.log('location:: ', this.location.path());

  console.log(' =============== window ===============');
  console.log('windowURL:' , window.location.href);
  console.log('windowPath:' , window.location.pathname);

}

奇怪现象 #

直接打印this.router.routerState.snapshot.url返回/，但展开console.log('ROUTER::', this.router);的日志时，里面的routerState.snapshot.url却是我需要的/first/second。

补充说明 #

我不想在服务内手动订阅，因为采用Rxjs声明式响应式方案，会将breadcrumbMenuItems$与其他布局Observable组合成layout vm$，仅在一处使用async管道订阅。

内容的提问来源于stack exchange，提问作者MG.