在 ngAfterViewInit 中调用时 ViewContainerRef 未定义

我想在父组件初始化时动态创建子组件，但是当我尝试在 ngAfterViewInit() 中创建它时，它会抛出 ViewContainerRef 未定义的错误。

组件.ts

  @ViewChild('container', {read: ViewContainerRef}) container: ViewContainerRef;

  constructor(private resolver: ComponentFactoryResolver) {
  }

  ngAfterViewInit(){
    const factory = this.resolver.resolveComponentFactory(ChildComponent);
    this.container.createComponent(factory); //container is undefined here

  }

组件.html

...
<div class="row" #container ></div>
...

自从div是在一个ngIf条件块，它可能不可用ngAfterViewInit。您可以通过监视元素的存在来保护代码免受这种可能性的影响ViewChildren和QueryList.changes event:

@ViewChildren('container', { read: ViewContainerRef }) containers: QueryList<ViewContainerRef>;

ngAfterViewInit() {
  if (this.containers.length > 0) {
    // The container already exists
    this.addComponent();
  };

  this.containers.changes.subscribe(() => {
    // The container has been added to the DOM
    this.addComponent();
  });
}

private addComponent() {
  const container = this.containers.first;
  const factory = this.resolver.resolveComponentFactory(ChildComponent);
  container.createComponent(factory);
}

See 这次堆栈闪电战 https://stackblitz.com/edit/angular-n61rj6进行演示。