formArray 中的可拖动 formGroups（反应式表单）

Posted 2023-05-08

【中文标题】formArray 中的可拖动 formGroups（反应式表单）

【英文标题】：Draggable formGroups in formArray (reactive forms)

【发布时间】：2019-10-02 14:30:59

【问题描述】：

在角度拖放模块中，他们提供了 moveItemInArray() 函数的文档，通过使用这个我们只能拖动数组中的内容。但是，我们如何在 formArray 中打乱（formGroups/formControls）？

即使我尝试了这个 moveItemInFormArray() 函数，正如这里提到的 https://github.com/angular/angular/issues/27171。但我不能让它工作。

groupDrag.component.html

    <form [formGroup]="exampleForm">
      <div formArrayName="formUnits" cdkDropList (cdkDropListDropped)="drop($event)" *ngFor="let unit of exampleForm.controls.formUnits.controls; let i=index" class="rowGroup">
        <div [formGroupName]="i" class="basic-container" cdkDrag>
          <div class="row row-container" >
            <button type="button" class="drag-handle" mat-icon-button cdkDragHandle>
              <mat-icon>unfold_more</mat-icon>
            </button>

            <!-- label input field -->
            <mat-form-field  class="col-lg-4"> 
              <input matInput placeholder="Please enter label without spaces" formControlName="label" required>  
            </mat-form-field>

            <!-- options input field -->
              <mat-form-field  class="col-lg-3"> 
                <input matInput placeholder="Enter Placeholdertext" formControlName="placeholder">
             </mat-form-field>

          </div>
        </div>
      </div>
    </form>

groupDrag.component.ts

drop(event: CdkDragDrop<FormGroup[]>) 
  console.log('drop event triggers')
  this.formArray = this.exampleForm.get('formUnits') as FormArray;
  const from = event.previousIndex;
  const to = event.currentIndex;
  this.moveItemInFormArray(this.formArray, from, to)


/**
* 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.
*/
moveItemInFormArray(formArray: FormArray, fromIndex: number, toIndex: number): void 
  const from = this.clamp(fromIndex, formArray.length - 1);
  const to = this.clamp(toIndex, formArray.length - 1);

  if (from === to) 
    return;
  

  const delta = from > to ? 1 : -1;
  for (let i = from; i * delta < to * delta; i += delta) 
    const previous = formArray.at(i);
    const current = formArray.at(i + delta);
    formArray.setControl(i, current);
    formArray.setControl(i + delta, previous);
  


/** Clamps a number between zero and a maximum. */
clamp(value: number, max: number): number 
  return Math.max(0, Math.min(max, value));

【参考方案1】：

这是工作示例：

groupDrag.component.ts

import moveItemInFormArray from "./move-item-in-form-array";

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

move-item-in-form-array.ts

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 from = fromIndex;
  const to = toIndex;

  const temp = formArray.at(from);
  for (let i = from; i * dir < to * dir; i = i + dir) 
    const current = formArray.at(i + dir);
    formArray.setControl(i, current);
  
  formArray.setControl(to, temp);

【讨论】：

this.arrayControls 必须更新为您的数组，但非常感谢！

【参考方案2】：

这是我的工作解决方案

在component.html中

    <form [formGroup]="exampleForm">
      <div cdkDropList (cdkDropListDropped)="drop($event)">
        <div formArrayName="formUnits" class="rowGroup"
          *ngFor="let unit of exampleForm.controls.formUnits.controls; let i=index"  
           cdkDrag>
          <div [formGroupName]="i" class="basic-container" cdkDrag>
            <div class="row row-container" >
              <button type="button" class="drag-handle" mat-icon-button cdkDragHandle>
                <mat-icon>unfold_more</mat-icon>
              </button>

              <!-- label input field -->
              <mat-form-field  class="col-lg-4"> 
                <input matInput placeholder="Please enter label without spaces" 
                formControlName="label" required>  
              </mat-form-field>

              <!-- options input field -->
              <mat-form-field  class="col-lg-3"> 
                <input matInput placeholder="Enter Placeholdertext" formControlName="placeholder">
             </mat-form-field>

          </div>
        </div>
      </div>
    </div>
   </form>

在component.ts文件中

  drop(event: CdkDragDrop<string[]>) 
    this.formArray = this.exampleForm.get('formUnits') as FormArray;
    const from = event.previousIndex;
    const to = event.currentIndex;
    this.moveItemInFormArray(this.formArray, from, to);
  

  /**
 * 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.
 */
  moveItemInFormArray(formArray: FormArray, fromIndex: number, toIndex: number): void 
    const from = this.clamp(fromIndex, formArray.length - 1);
    const to = this.clamp(toIndex, formArray.length - 1);

    if (from === to) 
      return;
    

    const previous = formArray.at(from);
    const current = formArray.at(to);
    formArray.setControl(to, previous);
    formArray.setControl(from, current);
  

  /** Clamps a number between zero and a maximum. */
  clamp(value: number, max: number): number 
    return Math.max(0, Math.min(max, value));
  

【讨论】：

作为参考，这个链接很有用。在 AngularInDepth link.medium.com/ONGISEADi5

中使用 tim_deschryver 的新 Angular Material CDK 探索拖放

在我的情况下，我从 中删除了“cdkDrag”以解决索引问题