CODEWITHSUNDEEP
javascripthtmlangulardrag-and-dropangular-cdk
Skdy
Skdy

Reputation: 290

Angular cdkDropList drag element restriction

I am currently using Angular 2 and a drag and drop module from https://material.angular.io/cdk/drag-drop/overview. I have made the drag and drop features work. I have two different types of class objects that i desire to be limited to their own types of drag and drop lists.

This could very likely be solved with grouping the lists but since I am using recursion other issues came up...

Currently I am having every lists inside the same group, meaning that anything can be dragged and dropped in every list (cdkDropListGroup, is positioned in a component before the recursion part is performed).

I am trying to make the lists restricted to only accept either Element or Attribute (but not both), but I have no idea of how to do this...

I have the following:

Classes:

export class Attribute {
name: string;
type: string;

}

export class Element {
    id: number;
    name: string;
    elements: Element[]
    attributes: Attribute[];

}

HTML:

<div > 
Elements             
<div
  cdkDropList    
  [cdkDropListData]="elements"
  class="example-list"
  (cdkDropListDropped)="drop($event)"
  [cdkDropListEnterPredicate]="isElement">
<div type="button" text-align="right" class="btn btnNotInline" (click)="addNewElement()">
  <img src="assets/img/IconPlus.png" class="elementListIcon"></div>
<div *ngFor="let element of elements" class="example-box" cdkDrag>
  <mat-list>
    <mat-list-item> 
      <mat-form-field appearance="standard dense" class="example-container">
        <input matInput placeholder="{{element.name}}"> 
      </mat-form-field>
    </mat-list-item>
    <mat-list-item>
      <div
        cdkDropList
        [cdkDropListData]="attributes"
        class="cdk-drag-list-attributes"
        (cdkDropListDropped)="drop($event)"
        [cdkDropListEnterPredicate]="isAttribute">
        <div type="button" text-align="right" class="btn btnNotInline" (click)="addNewAttribute()">
          <img src="assets/img/IconPlusPurple.png" class="elementListIcon"></div>
        <div *ngFor="let attribute of attributes" class="example-container" cdkDrag>
          <p class="mat-input-element-attribute">  
            <input matInput placeholder="{{attribute.name}}">
            <input matInput placeholder="{{attribute.type}}">
          </p> 
        </div>
      </div>
    </mat-list-item>
    <mat-list-item> 
        <app-listboardelement [attributes]="element.attributes" [elements]="element.elements"></app-listboardelement>
    </mat-list-item>
  </mat-list>
</div>

The ts. method being called (the attribute looks alike)

isElement(drag : CdkDrag){
      console.log("check " + (drag instanceof Element) +  typeof drag + " , "+ typeof drag.data + ", "+ drag.data + " , " +(drag.data instanceof Element));
      return (drag.data instanceof Element);
    }

from the output I simply gets: "check false object , undefined, undefined , false" From this I have tried to compare the dragged object with a class.. but I didn't have any luck.

Is there any way I can limit dragged object to certain lists dynamically? I know about [cdkDropListConnectedTo] but this gave me issues with the occuring recursion and the bindings. Any guidance would be appreciated

EDIT: Added image for presentation of how it is displayed - but does not work properly; enter image description here

Upvotes: 5

Views: 11175

Answers (2)

Marcus Kaseder
Marcus Kaseder

Reputation: 1198

The ts. method being called (the attribute looks alike)

isElement(drag : CdkDrag){
     console.log("check " + (drag instanceof Element) +  typeof drag + " , "+ typeof drag.data + ", "+ drag.data + " , " +(drag.data instanceof Element));
     return (drag.data instanceof Element);
   }

drag.data does not work, because you didn't assign any data to your cdkDrag via [cdkDragData]

<div *ngFor="let element of elements" class="example-box" cdkDrag [cdkDragData]="element">
 ...
</div>

To your question... You can either create two sets of cdkDropList arrays for elements and attributes and connect the list groups with the [cdkDropListConnectedTo] binding or connect all lists together in one array and allow the drop with the [cdkDropListEnterPredicate]="isElement" you already mentioned.

To solve the problem regarding recursion, you need to do some additional steps and check if the current drop container is the right one.

I've a detailed description in my question regarding nesting.

Angular Nested Drag and Drop / CDK Material cdkDropListGroup cdkDropList nested

Upvotes: 0

freepowder
freepowder

Reputation: 417

You can always check the drag-n-drop 'origin to destination' containers and take action accordingly, something like :

  drop(event: CdkDragDrop<string[]>) {
    // same container (just reorder items)
    if (event.previousContainer === event.container) {
        moveItemInArray(event.container.data, event.previousIndex, event.currentIndex);
    } else {
        // from first list to second list
        if (event.previousContainer.id === 'cdk-drop-list-0' && event.container.id === 'cdk-drop-list-1') {
            // do something
        }
        // from second list to first list
        if (event.previousContainer.id === 'cdk-drop-list-1' && event.container.id === 'cdk-drop-list-0') {
            // do something
        }
    }
}

Hope this helps!

Upvotes: 0

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