@ContentChildren没有在自定义组件中拾取项目

Question

我正在尝试使用标签@ContentChildren来拾取所有物品#buttonItem.

@ContentChildren('buttonItem', { descendants: true })

当我们直接在父组件中包含ref项时,这是有效的.

<!-- @ContentChildren returns child item -->
<parent-component>
  <button #buttonItem></button>
<parent-component>

但是,如果带有#buttonItemref 的元素包含在自定义组件中,@ContentChildren即使我设置了该{descendants: true}选项,也不会被选中.

<!-- @ContentChildren returns empty -->
<parent-component>
  <child-component-with-button-ref></child-component-with-button-ref>
<parent-component>

我创建了一个简单的StackBlitz示例来演示这一点.

Answer 1

似乎没有通过 github 解决此项目的时间表...我还发现了一条评论，指出您无法跨 ng-content 边界进行查询。

https://github.com/angular/angular/issues/14320#issuecomment-278228336

下面是使元素从OptionPickerComponent.

在那里OptionPickerComponent计数#listItem并发出数组AfterContentInit

 @Output() grandchildElements = new EventEmitter();     
 @ViewChildren('listItem') _items

  ngAfterContentInit() {
    setTimeout(() => {
        this.grandchildElements.emit(this._items)
    })
  } 

设置模板引用#picker，注册(grandchildElements)事件并将其设置$event为picker.grandchildElements

 <app-option-picker #picker [optionList]="[1, 2, 3]" (grandchildElements)="picker.grandchildElements = $event" popup-content>

创建输入以PopupComponent接受来自的值picker.grandchildElements

@Input('grandchildElements') grandchildElements: any

接受输入app.component.html​picker.grandchildElements

<app-popup [grandchildElements]="picker.grandchildElements">

popup.component设置console.log为打开和关闭

open() {
    if (this.grandchildElements) {
      console.log(this.grandchildElements);
    }
    else {
      console.log(this.childItems);
    }

 close() {
     if (this.grandchildElements) {
      console.log(this.grandchildElements);
    }
    else {
      console.log(this.childItems);
    }

popup.component把你的ContentChildren背改成listItem

@ContentChildren('listItem', { descendants: true }) childItems: Element;

popup.component.html设置标题表达式

<h3>Child Items: {{grandchildElements ? grandchildElements.length : childItems.length}}</h3>

斯塔克闪电战

https://stackblitz.com/edit/angular-popup-child-selection-issue-bjhjds?embed=1&file=src/app/option-picker/option-picker.component.ts