Angular 嵌套拖放 / CDK Material cdkDropListGroup cdkDropList 嵌套

Question

我使用 CDK Material 拖放实用程序来创建一个支持拖放的表单编辑器。

它工作正常，但在 cdkDropListGroup 中嵌套 cdkDropList 不起作用。我无法将任何内容拖到嵌套的下拉列表容器中。

<div class="container">
  <div class="row" cdkDropListGroup>
    <div class="col-2">
      <div id="toolbox" cdkDropList>
        ...
      </div>
    </div>
    <div class="col-10">
      <div id="formContainer" cdkDropList>
        ...
        <div class="row">
          <div class="col-md-6" cdkDropList>
            ... column 1 content
          </div>
          <div class="col-md-6" cdkDropList>
            ... column 1 content
          </div>
        </div>
      </div>
    </div>
  </div>
</div>

Answer 1

我花了一些时间，但由于这些帖子的提示，我终于找到了解决方案：

https://github.com/angular/components/issues/14093#issuecomment-462395200

问题是 cdkDropListGroup 不支持嵌套的下拉列表。您需要使用 [cdkDropListConnectedTo] 绑定连接下拉列表。

但是如果您只将列表连接到数组以进行 [cdkDropListConnectedTo] 绑定，则列表顺序会影响放置行为。此外，在嵌套下拉列表中排序将不起作用。

为避免这些问题，您需要创建一个在拖动时寻找正确 cdkDropList 的服务。

export class DragDropService {
  dropLists: CdkDropList[] = [];
  currentHoverDropListId?: string;

  constructor(@Inject(DOCUMENT) private document: Document) {}

  public register(dropList: CdkDropList) {
    this.dropLists.push(dropList);
  }

  dragMoved(event: CdkDragMove<IFormControl>) {
    let elementFromPoint = this.document.elementFromPoint(
      event.pointerPosition.x,
      event.pointerPosition.y
    );

    if (!elementFromPoint) {
      this.currentHoverDropListId = undefined;
      return;
    }

    let dropList = elementFromPoint.classList.contains('cdk-drop-list')
      ? elementFromPoint
      : elementFromPoint.closest('.cdk-drop-list');

    if (!dropList) {
      this.currentHoverDropListId = undefined;
      return;
    }

    this.currentHoverDropListId = dropList.id;
  }

  dragReleased(event: CdkDragRelease) {
    this.currentHoverDropListId = undefined;
  }
}

register 向每个 cdkDropList.
使用的 dropList 数组添加一个新的下拉列表
dragMoved 确定鼠标指针下方的正确 cdkDropList。

最好的办法是创建一个包含 cdkDropList.

的自己的组件

以下组件仅用于简单和演示目的。您不应直接使用服务属性。

<div
  *ngIf="container"
  cdkDropList
  [cdkDropListData]="container.controls"
  [cdkDropListConnectedTo]="dragDropService.dropLists"
  [cdkDropListEnterPredicate]="allowDropPredicate"
  (cdkDropListDropped)="dropped($event)"
>
  <div
    *ngFor="let item of container.controls"
    cdkDrag
    [cdkDragData]="item"
    (cdkDragMoved)="dragMoved($event)"
    (cdkDragReleased)="dragReleased($event)"
  >
    Drag Content
  </div>
</div>

export class FormContainerComponent implements OnInit, AfterViewInit {
  @ViewChild(CdkDropList) dropList?: CdkDropList;
  @Input() container: IFormContainer | undefined;

  allowDropPredicate = (drag: CdkDrag, drop: CdkDropList) => {
    return this.isDropAllowed(drag, drop);
  };

  constructor(
    public dragDropService: DragDropService
  ) {}
  ngOnInit(): void {}

  ngAfterViewInit(): void {
    if (this.dropList) {
      this.dragDropService.register(this.dropList);
    }
  }
  dropped(event: CdkDragDrop<IFormControl[]>) {
    // Your drop logic
  }

  isDropAllowed(drag: CdkDrag, drop: CdkDropList) {
    if (this.dragDropService.currentHoverDropListId == null) {
      return true;
    }

    return drop.id === this.dragDropService.currentHoverDropListId;
  }

  dragMoved(event: CdkDragMove<IFormControl>) {
    this.dragDropService.dragMoved(event);
  }

  dragReleased(event: CdkDragRelease) {
    this.dragDropService.dragReleased(event);
  }
}

每当 cdkDrag 移动时，dragMoved 确定正确的 cdkDropList
每当cdkDrag被释放时，重置确定的cdkDropList
最重要的方法是isDropAllowed方法，设置为[cdkDropListEnterPredicate]="allowDropPredicate"到cdkDropList
- 如前所述，cdk material 无法确定正确的下拉列表。
- 如果 cdk 选择了错误的下拉列表，我们只是通过返回 false 不允许 删除。在这种情况下，cdk 会自动选择下一个可能的 cdkDropList，这是正确的 :)

Angular 嵌套拖放 / CDK Material cdkDropListGroup cdkDropList 嵌套

Angular Nested Drag and Drop / CDK Material cdkDropListGroup cdkDropList nested

angular

angular-material

drag-and-drop

angular-cdk