Angular ngIf firebase身份验证指令使DOM无响应

html的

<div class="right-side">
    <!-- Header Widget -->
    <div class="header-widget">

    <!-- User Menu -->
    <div class="user-menu" *ngIf="afAuth.authState | async as user; else showLogin">
        <div class="user-name"><span><img src="assets/images/agent-03.jpg" alt=""></span>Hi,{{ ... }}!</div>
        <ul>
            <li><a routerLink="my/profile"><i class="sl sl-icon-user"></i> My Profile</a></li>
            <li><a routerLink="my/bookmarks"><i class="sl sl-icon-star"></i> Bookmarks</a></li>
            <li><a routerLink="my/properties"><i class="sl sl-icon-docs"></i> My Properties</a></li>
            <li (click)="logOut()"><a routerLink="/"><i class="sl sl-icon-power"></i> Log Out</a></li>
        </ul>
    </div>

    <ng-template #showLogin>
        <a routerLink="/login-register" class="sign-in"><i class="fa fa-user"></i> Log In / Register</a>
    </ng-template>

    <a routerLink="/submit-property" class="button border">Submit Property</a>
    </div>
    <!-- Header Widget / End -->
</div>

.TS

import { AngularFireAuth } from 'angularfire2/auth';
// ...
@Component({
  // ...
})
export class AppComponent {
  constructor(public afAuth: AngularFireAuth) {
  }

单击时,将弹出用户菜单并显示链接列表.但是,点击This is the template I’m using后没有响应.这是菜单ul的.css代码：

的CSS

.user-menu ul {
    float: left;
    text-align: left;
    position: absolute;
    top: 45px;
    right: 0;
    list-style: none;
    background-color: #fff;
    box-shadow: 0px 0px 10px 0px rgba(0,0.12);
    border-radius: 4px;
    display: inline-block;
    width: 190px;
    font-size: 15px;
    transform: translate3d(0,15px,0);
    padding: 16px 8px;
    box-sizing: border-box;
    transition: 0.25s;
    visibility: hidden;
    opacity: 0;
    z-index: 110;
}

如果我替换* ngIf指令中的代码,如此< div class =“user-menu”* ngIf =“1 == 1; else showLogin”>,则DOM响应：

但是,当我监视用户的身份验证状态* ngIf =“afAuth.authState | async as user; else showLogin”时,它会保持无响应状态.

怎么解决这个问题？