Multi-Select Drag and Drop in Angular - A Complete Implementation Guide

What is Multi-Select Drag and Drop in Angular?#

Multi-select drag and drop is a UI pattern that allows users to select multiple items at once and move them between lists using either drag gestures or button controls. Unlike standard drag and drop that only moves one item at a time, multi-select provides a more efficient way to organize large datasets, making it perfect for task management, content organization, and data categorization interfaces.

Why standard drag and drop isn't enough: Angular Material's CDK provides basic drag and drop functionality, but doesn't natively support moving multiple selected items simultaneously. Our implementation solves this common limitation.

What We're Building#

By the end of this tutorial, you'll create an Angular component that allows users to:

1. Select multiple items across two lists
2. Drag any selected item to move the entire selection
3. Use buttons as an alternative to drag gestures
4. See clear visual feedback for selected items

GitHub Repository: Complete Source Code Available Here#

Common Angular Drag and Drop Errors (And How To Fix Them)#

Before we dive into the implementation, let's address some frequent issues developers encounter:

Error	Common Cause	Solution
"Cannot read properties of undefined (reading 'data')"	Incorrect list references	Ensure your template correctly references list variables with #leftList and #rightList
Items won't drag between lists	Missing connection	Verify [cdkDropListConnectedTo] arrays include all target lists
Multi-selected items not moving together	Selection state not tracked	Implement separate arrays to track selected items
Selection not visually indicated	Missing CSS	Add .selected class styling with prominent visual indicators
Performance issues with large lists	DOM overload	Implement virtual scrolling for lists with >100 items

Starting with Project Setup#

First things first, let's set up our environment:

# Create a new Angular project
ng new angular-material-drag-drop-poc --routing=true --style=scss

# Navigate to project directory
cd angular-material-drag-drop-poc

# Add Angular Material
ng add @angular/material

# Install Angular CDK if not already included
npm install @angular/cdk

The Angular CDK (Component Dev Kit) provides the core drag-and-drop functionality we'll be using, while Angular Material gives us nice-looking UI components.

Understanding Our Data Structure#

We need a simple interface to represent the items in our lists:

// Item model
export interface Item {
  id: number
  name: string
  // Add more properties as needed for your use case
}

Each item has a unique ID and a name. In a real application, you might add more properties depending on what you're displaying.

Component Structure: Managing Two Lists#

Our component needs to track two things:

1. The items in each list
2. Which items are currently selected in each list

Here's how we set up the component class:

import { Component, OnInit } from '@angular/core'
import { CdkDragDrop, moveItemInArray, transferArrayItem } from '@angular/cdk/drag-drop'
import { Item } from './item.model'

@Component({
  selector: 'app-drag-drop-lists',
  templateUrl: './drag-drop-lists.component.html',
  styleUrls: ['./drag-drop-lists.component.scss'],
})
export class DragDropListsComponent implements OnInit {
  // Data for our two lists
  leftItems: Item[] = []
  rightItems: Item[] = []

  // Track which items are selected in each list
  selectedLeftItems: Item[] = []
  selectedRightItems: Item[] = []

  ngOnInit(): void {
    // Initialize with sample data
    this.leftItems = [
      { id: 1, name: 'Item 1' },
      { id: 2, name: 'Item 2' },
      { id: 3, name: 'Item 3' },
      { id: 4, name: 'Item 4' },
      { id: 5, name: 'Item 5' },
      { id: 6, name: 'Item 6' },
      { id: 7, name: 'Item 7' },
      { id: 8, name: 'Item 8' },
    ]
    this.rightItems = [
      { id: 9, name: 'Item 9' },
      { id: 10, name: 'Item 10' },
    ]
  }
}

Notice how we're maintaining separate arrays for the items and the selected items. This separation is crucial for our multi-select functionality.

Building the HTML Template#

Now, let's create the UI with two lists and action buttons between them:

<div class="drag-drop-container">
  <!-- Left List -->
  <div class="list-container">
    <mat-card>
      <mat-card-header>
        <mat-card-title>Source List</mat-card-title>
      </mat-card-header>
      <mat-card-content>
        <div
          cdkDropList
          #leftList="cdkDropList"
          [cdkDropListData]="leftItems"
          [cdkDropListConnectedTo]="[rightList]"
          class="item-list"
          (cdkDropListDropped)="drop($event)"
        >
          <div
            *ngFor="let item of leftItems; trackBy: trackById"
            class="item-box"
            cdkDrag
            [cdkDragData]="item"
            [class.selected]="isSelected(item, 'left')"
            (click)="toggleSelect(item, 'left')"
          >
            {{ item.name }}
          </div>
        </div>
      </mat-card-content>
    </mat-card>
  </div>

  <!-- Action Buttons -->
  <div class="action-buttons">
    <button
      mat-raised-button
      color="primary"
      (click)="moveSelectedToRight()"
      [disabled]="!hasSelectedItems('left')"
    >
      <mat-icon>arrow_forward</mat-icon> Move to Right
    </button>
    <button
      mat-raised-button
      color="accent"
      (click)="moveSelectedToLeft()"
      [disabled]="!hasSelectedItems('right')"
    >
      <mat-icon>arrow_back</mat-icon> Move to Left
    </button>
  </div>

  <!-- Right List -->
  <div class="list-container">
    <mat-card>
      <mat-card-header>
        <mat-card-title>Target List</mat-card-title>
      </mat-card-header>
      <mat-card-content>
        <div
          cdkDropList
          #rightList="cdkDropList"
          [cdkDropListData]="rightItems"
          [cdkDropListConnectedTo]="[leftList]"
          class="item-list"
          (cdkDropListDropped)="drop($event)"
        >
          <div
            *ngFor="let item of rightItems; trackBy: trackById"
            class="item-box"
            cdkDrag
            [cdkDragData]="item"
            [class.selected]="isSelected(item, 'right')"
            (click)="toggleSelect(item, 'right')"
          >
            {{ item.name }}
          </div>
        </div>
      </mat-card-content>
    </mat-card>
  </div>
</div>

Breaking down the key parts:

1. The cdkDropList directive makes our container a drop target
2. We connect the two lists with [cdkDropListConnectedTo]
3. Each item gets the cdkDrag directive to make it draggable
4. We add a (click) handler to toggle selection
5. The [class.selected] binding applies styling to selected items
6. Buttons call methods to move selected items between lists
7. We've added trackBy for performance optimization

Selection Functionality#

The core of our multi-select feature is the ability to select items by clicking on them:

/**
 * Toggle selection state of an item
 */
toggleSelect(item: Item, list: 'left' | 'right'): void {
  if (list === 'left') {
    const index = this.selectedLeftItems.findIndex(i => i.id === item.id);
    if (index === -1) {
      this.selectedLeftItems.push(item); // Select the item
    } else {
      this.selectedLeftItems.splice(index, 1); // Deselect the item
    }
  } else {
    // Same logic for right list
    const index = this.selectedRightItems.findIndex(i => i.id === item.id);
    if (index === -1) {
      this.selectedRightItems.push(item);
    } else {
      this.selectedRightItems.splice(index, 1);
    }
  }
}

/**
 * Check if an item is selected
 */
isSelected(item: Item, list: 'left' | 'right'): boolean {
  if (list === 'left') {
    return this.selectedLeftItems.some(i => i.id === item.id);
  } else {
    return this.selectedRightItems.some(i => i.id === item.id);
  }
}

/**
 * Check if there are any selected items in a list
 */
hasSelectedItems(list: 'left' | 'right'): boolean {
  return list === 'left'
    ? this.selectedLeftItems.length > 0
    : this.selectedRightItems.length > 0;
}

/**
 * Tracking function for ngFor performance
 */
trackById(index: number, item: Item): number {
  return item.id;
}

What's happening here:

• toggleSelect() adds or removes an item from the selection array
• isSelected() checks if an item is in the selection array
• hasSelectedItems() helps us enable/disable the transfer buttons
• trackById() optimizes rendering performance for large lists

The Heart of Drag and Drop#

The drop() method handles what happens when a user drops items:

/**
 * Handle drop events between lists
 */
drop(event: CdkDragDrop<Item[]>) {
  if (event.previousContainer === event.container) {
    // Reordering within the same list
    moveItemInArray(
      event.container.data,
      event.previousIndex,
      event.currentIndex
    );
  } else {
    // Moving between lists
    if (this.isSingleItemDrag(event)) {
      // Single item transfer
      transferArrayItem(
        event.previousContainer.data,
        event.container.data,
        event.previousIndex,
        event.currentIndex
      );
    } else {
      // Multi-item transfer - our custom logic
      this.handleMultiItemDrag(event);
    }
  }

  // Clear selections after completing the operation
  this.clearSelections();
}

/**
 * Check if this is a single item drag operation
 */
private isSingleItemDrag(event: CdkDragDrop<Item[]>): boolean {
  const sourceList = event.previousContainer.id === 'cdk-drop-list-0' ? 'left' : 'right';
  const draggedItem = event.item.data;

  // Check if the dragged item is part of a multi-selection
  return sourceList === 'left'
    ? !this.selectedLeftItems.some(item => item.id === draggedItem.id) || this.selectedLeftItems.length === 0
    : !this.selectedRightItems.some(item => item.id === draggedItem.id) || this.selectedRightItems.length === 0;
}

This is where things get interesting:

1. We first check if we're reordering within a list or moving between lists
2. If moving between lists, we decide whether this is a single item drag or a multi-item drag
3. For single items, we use the CDK's built-in transferArrayItem function
4. For multiple items, we need custom logic

The Multi-Item Drag Magic#

This is where the real magic happens - handling multiple selected items during a drag:

/**
 * Custom logic to handle dragging multiple selected items
 */
private handleMultiItemDrag(event: CdkDragDrop<Item[]>) {
  const sourceList = event.previousContainer.id === 'cdk-drop-list-0' ? 'left' : 'right';
  const draggedItem = event.item.data;
  const selectedItems = sourceList === 'left' ? this.selectedLeftItems : this.selectedRightItems;

  // Fall back to single item drag if the dragged item isn't in selection
  if (!selectedItems.some(item => item.id === draggedItem.id)) {
    transferArrayItem(
      event.previousContainer.data,
      event.container.data,
      event.previousIndex,
      event.currentIndex
    );
    return;
  }

  // Find indices of all selected items
  const selectedIndices = selectedItems.map(item =>
    event.previousContainer.data.findIndex(listItem => listItem.id === item.id)
  ).filter(index => index !== -1).sort((a, b) => a - b);

  // Move all selected items while adjusting for removed items
  for (let i = 0; i < selectedIndices.length; i++) {
    // Adjust index based on already removed items
    const adjustedIndex = selectedIndices[i] - i;
    const item = event.previousContainer.data[adjustedIndex];

    // Remove from source
    event.previousContainer.data.splice(adjustedIndex, 1);

    // Add to target at appropriate position
    const targetIndex = event.currentIndex > event.previousIndex
      ? event.currentIndex - i
      : event.currentIndex;
    event.container.data.splice(targetIndex, 0, item);
  }
}

Let's break down what's happening here:

1. We determine which list is the source and which items are selected
2. If the dragged item isn't in the selection, we fall back to single-item behavior
3. We find the indices of all selected items in the source list
4. We move each selected item one by one, carefully adjusting indices as we go
5. The trickiest part is adjusting indices since removing items changes the positions of subsequent items

Button-Based Transfer#

Not all users prefer drag-and-drop, so we also provide button controls for better accessibility:

/**
 * Move selected items from left to right
 */
moveSelectedToRight(): void {
  if (this.selectedLeftItems.length === 0) return;

  // Add selected items to right list
  this.rightItems = [...this.rightItems, ...this.selectedLeftItems];

  // Remove them from left list
  this.leftItems = this.leftItems.filter(
    item => !this.selectedLeftItems.some(selected => selected.id === item.id)
  );

  this.clearSelections();
}

/**
 * Move selected items from right to left
 */
moveSelectedToLeft(): void {
  if (this.selectedRightItems.length === 0) return;

  // Add selected items to left list
  this.leftItems = [...this.leftItems, ...this.selectedRightItems];

  // Remove them from right list
  this.rightItems = this.rightItems.filter(
    item => !this.selectedRightItems.some(selected => selected.id === item.id)
  );

  this.clearSelections();
}

/**
 * Clear all selections
 */
clearSelections(): void {
  this.selectedLeftItems = [];
  this.selectedRightItems = [];
}

These methods:

1. Add all selected items to the target list
2. Remove those items from the source list
3. Clear selections afterward

Styling the Interface#

The visual presentation is crucial for usability and user feedback:

.drag-drop-container {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 20px;
  padding: 20px 0;
}

.list-container {
  flex: 1;
  max-width: 400px;
  min-width: 250px;
}

.item-list {
  min-height: 400px;
  border: solid 1px #ccc;
  border-radius: 4px;
  background-color: white;
  overflow: auto;
}

.item-box {
  padding: 15px;
  border-bottom: solid 1px #ddd;
  border-left: 4px solid transparent;
  color: rgba(0, 0, 0, 0.87);
  cursor: pointer;
  background: white;
  transition: all 200ms cubic-bezier(0, 0, 0.2, 1);
  display: flex;
  align-items: center;
}

.item-box:hover {
  background-color: #f5f5f5;
}

// Highlighted state for selected items
.selected {
  background-color: #e3f2fd !important;
  border-left: 4px solid #1976d2 !important;
}

// Drag animation classes
.cdk-drag-preview {
  box-sizing: border-box;
  border-radius: 4px;
  box-shadow:
    0 5px 5px -3px rgba(0, 0, 0, 0.2),
    0 8px 10px 1px rgba(0, 0, 0, 0.14),
    0 3px 14px 2px rgba(0, 0, 0, 0.12);
}

.cdk-drag-placeholder {
  opacity: 0.3;
}

.cdk-drag-animating {
  transition: transform 250ms cubic-bezier(0, 0, 0.2, 1);
}

.action-buttons {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 10px;
}

/* Responsive design for mobile */
@media (max-width: 768px) {
  .drag-drop-container {
    flex-direction: column;
  }

  .list-container {
    max-width: 100%;
  }

  .action-buttons {
    flex-direction: row;
    padding: 10px 0;
  }
}

The key styling elements:

1. A flex container to position the lists and buttons
2. Clear visual feedback for selected items
3. Smooth animations and shadows for drag operations
4. Responsive design that adapts to mobile devices

Real-World Applications of Multi-Select Drag and Drop#

This pattern is extremely useful in many common interfaces:

1. Project Management Tools#

Move multiple tasks between sprint backlogs, or assign several stories to a developer at once.

interface Task {
  id: number
  title: string
  priority: 'high' | 'medium' | 'low'
  assignee?: string
}

2. Email Clients#

Select multiple emails and move them to different folders or apply bulk actions.

3. Content Management Systems#

Organize articles, posts, or media assets into different categories with multi-select capabilities.

4. E-commerce Admin Panels#

Categorize products by selecting multiple items and moving them to different collections.

5. Playlist Management#

Select multiple songs and add them to different playlists in music applications.

Performance Optimization for Large Lists#

If your lists contain hundreds of items, consider these optimizations:

// Implement virtual scrolling with Angular CDK
import { ScrollingModule } from '@angular/cdk/scrolling';

// In your template
<cdk-virtual-scroll-viewport itemSize="50" class="item-list">
  <div *cdkVirtualFor="let item of leftItems; trackBy: trackById"
       class="item-box"
       cdkDrag
       [cdkDragData]="item"
       [class.selected]="isSelected(item, 'left')"
       (click)="toggleSelect(item, 'left')">
    {{ item.name }}
  </div>
</cdk-virtual-scroll-viewport>

Keyboard Accessibility Enhancement#

To make our component fully accessible, let's add keyboard shortcuts:

@HostListener('window:keydown', ['$event'])
handleKeyboardEvent(event: KeyboardEvent): void {
  // Ctrl+Right Arrow to move selected items right
  if (event.ctrlKey && event.key === 'ArrowRight') {
    this.moveSelectedToRight();
    event.preventDefault();
  }

  // Ctrl+Left Arrow to move selected items left
  if (event.ctrlKey && event.key === 'ArrowLeft') {
    this.moveSelectedToLeft();
    event.preventDefault();
  }

  // Shift+Click for range selection would be implemented in the toggleSelect method
}

Integration with State Management#

For larger applications, you might want to integrate this with NgRx:

// Action definitions
export const moveItems = createAction(
  '[Drag Drop Component] Move Items',
  props<{ items: Item[], source: string, target: string }>()
);

// In your component
moveSelectedToRight(): void {
  if (this.selectedLeftItems.length === 0) return;

  this.store.dispatch(moveItems({
    items: this.selectedLeftItems,
    source: 'left',
    target: 'right'
  }));

  this.clearSelections();
}

Conclusion and Next Steps#

Building a multi-select drag-and-drop interface in Angular requires careful implementation, but the result is a powerful, intuitive UI that gives users flexibility in how they organize data. By allowing both gesture-based and button-based interactions, you can create accessible interfaces that work across devices and accommodate different user preferences.

Ready to take this further? Try these enhancements:

1. Add shift-click for range selection
2. Implement custom drag previews showing the number of selected items
3. Add filtering and search capabilities to the lists
4. Create animations when items move between lists
5. Add support for keyboard navigation within lists

Additional Resources#

• Official Angular CDK Drag & Drop Documentation
• Our Complete GitHub Repository

Have you implemented multi-select drag and drop in your Angular application? Share your experience in the comments below!

About the Author#

I'm a Senior Angular Developer with over 7 years of experience building enterprise applications. I specialize in creating intuitive, accessible user interfaces and sharing knowledge with the developer community. Follow me for more advanced Angular tutorials.

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This article was last updated on March 31, 2025