Javascript @ViewChild未创建角度CDK门户？

尝试创建CDK门户，如下所示：

@ViewChild(CdkPortal) portal;

但是，门户在

ngAfterViewInit

方法中未定义：

  ngAfterViewInit(): void {
    // Create a portalHost from a DOM element
    this.portalHost = new DomPortalHost(
      document.querySelector('#actions'),
      this.componentFactoryResolver,
      this.appRef,
      this.injector
    );

    console.log("THE PORTAL IS: ", this.portal)

---

有什么想法吗？

忘记导入门户模块：

import { PortalModule } from '@angular/cdk/portal';

...


@NgModule({
  imports:      [ PortalModule, MaterialModule, BrowserModule, FormsModule ],
  declarations: [ ToolbarActionsComponent, AppComponent, HelloComponent ],
  bootstrap:    [ AppComponent ]
})