僅在Angular 7中登錄后啟用注銷按鈕

Question

我僅在登錄https://stackblitz.com/edit/angular-login-hide-navbar-ngif后才引用以下鏈接來啟用注銷按鈕

我只想在用戶登錄后才在導航欄中顯示“注銷”，我正在通過從“身份驗證服務”中調用“ this.authservice.isUserLoggedIn”並將其分配給變量並寫入一個來驗證用戶是否登錄“注銷”鏈接附近的ngif條件。 我已經使用BehaviourSubject來獲取當前狀態。 但是我不知道為什么代碼不起作用，並且總是返回false，因此即使用戶登錄后也無法啟用“注銷”鏈接

我有header.component.ts

export class CommonheaderComponent implements OnInit {

  constructor(private authservice : AuthenticationService) { }
  isLoggedIn$ : Observable<boolean>;
  ngOnInit() {
    this.isLoggedIn$ = this.authservice.isUserLoggedIn;
  }
  }

我有如下的header.component.html

<ul class="nav navbar-nav">
      <li><a [routerLink]='["/search"]'>Search <span class="slider"></span></a></li>
      <li *ngIf="isLoggedIn"><a (click)="logout()">Logout</a></li>
  </ul>

以下是login.component.ts

export class LoginComponent implements OnInit {
  isLoggedIn : Observable<boolean>;

 ngOnInit() {
   this.isLoggedIn = this.authservice.isUserLoggedIn;
   this.loginForm = this.formbuilder.group({
    username : ['', Validators.required],
    password : ['', Validators.required]
  })
 }

}

  onSubmit(){
    this.authservice.login(this.loginForm.value).subscribe(data => {
  })    
 }
}

我有以下身份驗證服務

    import { Injectable } from '@angular/core';
    import { HttpClient, HttpHeaders } from '@angular/common/http';
    import { BehaviorSubject, Observable } from 'rxjs';
    import { map } from 'rxjs/operators';
    import { User } from '../_models/user';
    import { Router } from '@angular/router';

    const httpOptions =  {
      headers : new HttpHeaders({'Content-type' : 'application/json'})
    }

    @Injectable({
      providedIn: 'root'
    })
    export class AuthenticationService {
      private currentUserSubject : BehaviorSubject<User>;
      private currentUser : Observable<User>;
      private loggedIn: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);

      constructor(private http: HttpClient, private router: Router) {
        this.currentUserSubject = new BehaviorSubject<User>(JSON.parse(localStorage.getItem('currentUser')));
        this.currentUser = this.currentUserSubject.asObservable();
      }

      public get currentUserValue(): User{
        return this.currentUserSubject.value;
      }

      public login(user: User):Observable<any>{
        var baseUrl = "http://localhost:3000/";
        return this.http.post<any>(baseUrl+'auth/login', user, httpOptions).pipe(map(user => {
          if(user && user.accesstoken){
            localStorage.setItem('currentUser', JSON.stringify(user));
            this.currentUserSubject.next(user);
            this.loggedIn.next(true);
          }else{
            return false;
          }
          return user;
        }))
      }

      get isUserLoggedIn(){
          return this.loggedIn.asObservable();
      } 
    }

我在哪里犯錯了。 或為此的解決方案/替代方案。 請幫忙！！

很久以來我一直堅持

Answer 1

您可以像這樣更改模板后嘗試：

<ul class="nav navbar-nav">
      <li><a [routerLink]='["/search"]'>Search <span class="slider"></span></a></li>
      <li *ngIf="isLoggedIn$ | async"><a (click)="logout()">Logout</a></li>
  </ul>

注意async管道解包了可觀察的值。

請注意，在您共享的stackblitz示例中-可觀察的值已使用async管道展開-

<mat-toolbar color="primary" *ngIf="isLoggedIn$ | async as isLoggedIn">

Answer 2

對於您的最后一條評論，這是因為服務正在重新初始化並且您的觀察值已被重置。 將此添加到您的構造函數

if(localStorage.getItem('currentUser') != null)
    this.loggedIn.next(true);

這對我有用。