使用formArray进行 Angular 拖放

Question

我有 2 个数组。我正在实现一个 Angular 拖放，我想使用 FormArray 来保存元素被放入的数组。

问题是我不能将 formcontrol 应用到 div 因为它给出了错误

Error: No value accessor for form control with name: 'language'

这是html

      <div>

        <div class="example-container">
          <h2>Selected Languages</h2>
          <div
          cdkDropList
          #todoList="cdkDropList"
          [cdkDropListData]="anotherarray"
          [cdkDropListConnectedTo]="[doneList]"
          class="example-list"
          (cdkDropListDropped)="drop($event)"
           formControlName="language">
          <div class="list-group-item list-group-item-action " *ngFor="let item of anotherarray" cdkDrag>
            {{item}}
          </div>
        </div>
      </div>

      <div class="example-container">
        <h2>Available Languages</h2>

        <div
        cdkDropList
        #doneList="cdkDropList"
        [cdkDropListData]="testingarray"
        [cdkDropListConnectedTo]="[todoList]"
        class="example-list"
        (cdkDropListDropped)="drop($event)">
        <div class="list-group-item list-group-item-action " *ngFor="let item of testingarray" cdkDrag>{{item}}</div>
      </div>
      </div>

      </div>

      <button type="submit" class="btn btn-primary my-2" translate>saveButtonLabel
        <fa-icon *ngIf="saveIcon" [icon]="saveIcon" [spin]="saveIcon.iconName === 'spinner'"></fa-icon>
      </button>
    </form>

Answer 1

Angular Material 拖放 API 有一个 moveItemInArray 函数，如 here 所示
这仅支持常规数组，但根据 pierNik 的回答 here on StackOverflow ，您可以使用以下函数复制 FormArray 的功能:

import { FormArray } from '@angular/forms';

/**
 * Moves an item in a FormArray to another position.
 * @param formArray FormArray instance in which to move the item.
 * @param fromIndex Starting index of the item.
 * @param toIndex Index to which he item should be moved.
 */

export function moveItemInFormArray(
  formArray: FormArray,
  fromIndex: number,
  toIndex: number
): void {
  const dir = toIndex > fromIndex ? 1 : -1;

  const item = formArray.at(fromIndex);
  for (let i = fromIndex; i * dir < toIndex * dir; i = i + dir) {
    const current = formArray.at(i + dir);
    formArray.setControl(i, current);
  }
  formArray.setControl(toIndex, item);
}

然后在调用代码中传递 formArray 代替普通数组。

get formControls(): FormArray {
    return this.form.get('arrayName') as FormArray;
}

constructor() {
    this.form = this.formBuilder.group({
      arrayName: this.formBuilder.array([]),
    });
}

drop(event: CdkDragDrop<string[]>) {
    moveItemInFormArray(
      this.formControls,
      event.previousIndex,
      event.currentIndex
    );
  }

查看正在工作的 Stackblitz here