Angular反应形式-从HTML手动更新FormGroup

Question

我创建了一个角度组件，用于将文本插入文本字段或在当前插入符号位置输入。

import * as $ from 'jquery';
import { Component, ElementRef, EventEmitter, HostBinding, Input, OnInit, Output } from '@angular/core';

@Component({
  selector: 'app-special-character',
  templateUrl: './special-character.component.html',
  styleUrls: ['./special-character.component.scss']
})
export class SpecialCharacterComponent implements OnInit {
  @Input('character') private character:string;
  @HostBinding('class') @Input('class') classList: string = '';
  @Output() inserted = new EventEmitter();
  @Input('target') targetId: string;

  constructor(
    private readonly elementRef: ElementRef) {
  }

  insert(): boolean {
    // is there a character to insert?
    if (!this.character) return false;

    // get the target field
    const $target = $(this.targetId);

    // allow for properties not in document class
    const browserDocument: any = document;

    if (browserDocument.selection) {
      $target.focus();
      const range = browserDocument.selection.createRange();
      range.text = this.character;
    } else {
      // get the current state
      const selectionStart = $target.prop('selectionStart');
      const selectionEnd = $target.prop('selectionEnd');
      const value = $target.val();

      // set the new value
      $target.val(`${value.substring(0,     selectionStart)}${this.character}${value.substring(selectionEnd, value.length)}`);

      // set the cursor
      $target.prop('selectionStart', selectionStart + this.character.length);
      $target.prop('selectionEnd', selectionStart + this.character.length);
    }

    // now return to the target field
    $target.focus();

    return false;
  }

  ngAfterViewInit() {
    const $component = $(this.elementRef.nativeElement);

    // clear the classes from the component
    $component.removeClass();

    // get the button component
    const $button = $component.children().first();

    // add the classes
    $button.addClass(this.classList);

    // get the character to insert (if it isn't set manually)
    if (!this.character) this.character = $button.text();
  }

  ngOnInit() {
  }
}

该组件的html更新一个文本区域。

    <textarea class="form-control" formControlName="field1FillInTheGap" id="question" placeholder="eg. The capital of France is ___?"></textarea>
    <app-special-character class="btn btn-secondary btn-xs" character="___" target="#question">?</app-special-character>

文本插入可以正常工作，但是在插入文本后，关联的FormControl不会自动更新。我想手动触发与文本字段关联的反应式FormControl的更新和验证。我该怎么做？