Angular 角度2：如果框架未按预期加载

它是一个非常简单的应用程序，下面有一个工具栏和全屏iframe。在我开始动态设置iframe

src

之前，一切正常。下面是代码：
app.component.html

<md-toolbar class="toolbar">
  <span>Toolbar</span>
  <span class="spacer"></span>
  <button md-button (click)="updateDashboard(first_url)"  id="first" class="top-link">First Button</button>
  <button md-button  (click)="updateDashboard(second_url)" id="second" class="top-link">Second Button</button>
</md-toolbar>


<iframe id="report-frame" frameborder="0" [src]="dashboardUrl"></iframe>

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在updateDashboard方法中尝试这样做-

this.dashboardUrl=this.sanitizer.bypassSecurityTrustResourceUrl（url）没有运气…仍然看到相同的问题。
export class AppComponent {
  dashboardUrl: SafeUrl;
  constructor(private sanitizer: DomSanitizer) {}
  private first_url: string = "https://www.google.com/"
  private second_url:string="https://reddit.com"
  updateDashboard(url: string) {
    this.sanitizer.bypassSecurityTrustResourceUrl(url);
  }
 }