如何以编程方式扩展一个动态添加的mat-expansion-panel？

Question

我正在尝试使用*ngFor在Mat-accordian中显示多个Mat-expansion-panel。我需要添加一个新的垫-扩展-面板上的一个按钮，我能够做到。我还需要在点击按钮时展开(打开)这个新添加的扩展面板，而这是我无法实现的。请帮帮忙。

Stackblitz - https://stackblitz.com/edit/angular-fh5vu1-g6phe6?file=app%2Fexpansion-steps-example.ts

export class ExpansionStepsExample { 
  items: number[] = [1,2,3];

  AddNewRow() {
    this.items.push(4);
  }
}

<mat-accordion class="example-headers-align">
  <mat-expansion-panel *ngFor="let item of items;">
    <mat-expansion-panel-header>
      <mat-panel-title> {{item}} </mat-panel-title>
    </mat-expansion-panel-header>
    {{item}}
  </mat-expansion-panel>
</mat-accordion>
<button (click)="AddNewRow()" value="Add New"> Add New </button>

Answer 1

我建议更改您的数据模型。通过这种方式，您可以存储打开和关闭的状态，以及每个项目的编号。

item = [
  {
    number: 1, 
    open: false
  },
  {
    number: 2,
    open: true
  }
];

  AddNewRow() {
     this.item.push({number: 3, open: true});
   }

<mat-accordion class="example-headers-align" multi="true">
   <mat-expansion-panel *ngFor="let item of items;" [expanded]="item.open" >
      <mat-expansion-panel-header>
         <mat-panel-title> {{item. number}} </mat-panel-title>
      </mat-expansion-panel-header>
         {{item.number }}
   </mat-expansion-panel>
</mat-accordion>
<button (click)="AddNewRow()" value="Add New"> Add New </button>

Answer 2

您可以访问Material Expansion Panel元素，并调用open()和close()方法。

​

import { Component, OnInit, ViewChild } from '@angular/core';
import { MatExpansionPanel } from '@angular/material';
...
@ViewChild(MatExpansionPanel, {static: true}) matExpansionPanelElement: MatExpansionPanel;
...
selectItem() {
    this.matExpansionPanelElement.close(); //open()
}

<mat-accordion>
    <mat-expansion-panel #matExpansionPanel>
    ...
    </mat-expansion-panel>
</mat-accordion>

​

Answer 3

对@sem针对Angular 9+用法的答案做了一个小小的更改: component.ts

@ViewChild('matExpansionPanel', { static: true }) matExpansionPanelElement: MatExpansionPanel;

component.html

<mat-expansion-panel #matExpansionPanel>