Restrict drag and drop nodes in Angular TreeView component

27 Aug 202511 minutes to read

You are able to restrict drag and drop operations to allow files to be dropped only under folders. This can be achieved by using nodeDragStop and nodeDragging events of TreeView.

Implementation approach

To restrict drag and drop operations:

1. Enable drag and drop: Set the allowDragAndDrop property to true
2. Handle nodeDragging event: Use this event to provide visual feedback by modifying drop indicators
3. Handle nodeDragStop event: Implement validation logic to cancel invalid drop operations
4. Node type identification: Determine whether nodes are files or folders using node data properties
5. Conditional validation: Allow drops only when the target node meets the specified criteria

app.component.ts

import { NgModule } from '@angular/core'
import { BrowserModule } from '@angular/platform-browser'
import { FormsModule } from '@angular/forms'
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations'
import { Component, Inject, ViewChild } from '@angular/core';
import { DragAndDropEventArgs } from '@syncfusion/ej2-angular-navigations';

@Component({
    imports: [
        FormsModule, TreeViewModule
    ],
    standalone: true,
    selector: 'app-container',
    template: `<div id='treeparent'><ejs-treeview id="icons" [fields]='field' sortOder='Ascending' allowDragAndDrop='allowDragAndDrop' (nodeDragStop)='dragStop($event)' (nodeDragging)='nodeDrag($event)'></ejs-treeview></div>`
})
export class AppComponent {
    // Hierarchical data source for TreeView component
    public hierarchicalData: Object[] = [
        {
            nodeId: '01', nodeText: 'Music', icon: 'folder',
            nodeChild: [
                { nodeId: '01-01', nodeText: 'Gouttes.mp3', icon: 'audio' }
            ]
        },
        {
            nodeId: '02', nodeText: 'Videos', icon: 'folder',
            nodeChild: [
                { nodeId: '02-01', nodeText: 'Naturals.mp4', icon: 'video' },
                { nodeId: '02-02', nodeText: 'Wild.mpeg', icon: 'video' },
            ]
        },
        {
            nodeId: '03', nodeText: 'Documents', icon: 'folder',
            nodeChild: [
                { nodeId: '03-01', nodeText: 'Environment Pollution.docx', icon: 'docx' },
                { nodeId: '03-02', nodeText: 'Global Water, Sanitation, & Hygiene.docx', icon: 'docx' },
                { nodeId: '03-03', nodeText: 'Global Warming.ppt', icon: 'ppt' },
                { nodeId: '03-04', nodeText: 'Social Network.pdf', icon: 'pdf' },
                { nodeId: '03-05', nodeText: 'Youth Empowerment.pdf', icon: 'pdf' },
            ]
        },
        {
            nodeId: '04', nodeText: 'Pictures', icon: 'folder', expanded: true,
            nodeChild: [
                {
                    nodeId: '04-01', nodeText: 'Camera Roll', icon: 'folder', expanded: true,
                    nodeChild: [
                        { nodeId: '04-01-01', nodeText: 'WIN_20160726_094117.JPG', image: 'https://ej2.syncfusion.com/demos/src/treeview/images/employees/9.png' },
                        { nodeId: '04-01-02', nodeText: 'WIN_20160726_094118.JPG', image: 'https://ej2.syncfusion.com/demos/src/treeview/images/employees/3.png' },
                    ]
                },
                { nodeId: '04-02', nodeText: 'Wind.jpg', icon: 'images' },
                { nodeId: '04-03', nodeText: 'Stone.jpg', icon: 'images' },
            ]
        },
        {
            nodeId: '05', nodeText: 'Downloads', icon: 'folder',
            nodeChild: [
                { nodeId: '05-01', nodeText: 'UI-Guide.pdf', icon: 'pdf' },
                { nodeId: '05-02', nodeText: 'Tutorials.zip', icon: 'zip' },
                { nodeId: '05-03', nodeText: 'Game.exe', icon: 'exe' },
                { nodeId: '05-04', nodeText: 'TypeScript.7z', icon: 'zip' },
            ]
        }
    ];
    public field: Object = { dataSource: this.hierarchicalData, id: 'nodeId', text: 'nodeText', child: 'nodeChild', iconCss: 'icon', imageUrl: 'image' };
    public allowDragAndDrop: boolean = true;

    public nodeDrag(args: DragAndDropEventArgs): void {
        if (args.droppedNode != null && args.droppedNode.getElementsByClassName('folder') && args.droppedNode.getElementsByClassName('folder').length === 0) {
            args.dropIndicator = 'e-no-drop';
        }
    }

    public dragStop(args: DragAndDropEventArgs): void {
        if (args.droppedNode != null && args.droppedNode.getElementsByClassName('folder') && args.droppedNode.getElementsByClassName('folder').length === 0) {
            args.cancel = true;
        }
    }


}

styles.css

@import 'node_modules/@syncfusion/ej2-base/styles/material.css';
@import 'node_modules/@syncfusion/ej2-inputs/styles/material.css';
@import 'node_modules/@syncfusion/ej2-buttons/styles/material.css';
@import 'node_modules/@syncfusion/ej2-angular-base/styles/material.css';
@import 'node_modules/@syncfusion/ej2-angular-navigations/styles/material.css';
@import 'node_modules/@syncfusion/ej2-angular-inputs/styles/material.css';

#treeparent {
    display: block;
    max-width: 400px;
    max-height: 320px;
    margin: auto;
    overflow: auto;
    border: 1px solid #dddddd;
    border-radius: 3px;
}

.e-treeview .e-list-img {
    width: 25px;
    height: 25px;
}

/* Loading sprite image for TreeView */
.e-treeview .e-list-icon {
    background-repeat: no-repeat;
    background-image: url(https://ej2.syncfusion.com/demos/src/treeview/images/icons/file_icons.png);
    height: 20px;
}

/* Specify the icon positions based upon class name */
.e-treeview .e-list-icon.folder {
    background-position: -10px -552px;
}

.e-treeview .e-list-icon.docx {
    background-position: -10px -20px;
}

.e-treeview .e-list-icon.ppt {
    background-position: -10px -48px;
}

.e-treeview .e-list-icon.pdf {
    background-position: -10px -104px;
}

.e-treeview .e-list-icon.images {
    background-position: -10px -132px;
}

.e-treeview .e-list-icon.zip {
    background-position: -10px -188px;
}

.e-treeview .e-list-icon.audio {
    background-position: -10px -244px;
}

.e-treeview .e-list-icon.video {
    background-position: -10px -272px;
}

.e-treeview .e-list-icon.exe {
    background-position: -10px -412px;
}

main.ts

import { bootstrapApplication } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import 'zone.js';
bootstrapApplication(AppComponent).catch((err) => console.error(err));