Auto hide show expand collapse icon in Angular TreeView component

7 Jan 20257 minutes to read

You can display the expand icon by hovering the mouse over the TreeView and hide the expand icon by leaving the mouse from the TreeView using the created event. Refer to the following code sample to hide/show the expand/collapse icon automatically using the mouse.

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 { TreeViewComponent } from '@syncfusion/ej2-angular-navigations';
/**
 * TreeView Auto hide/show expand/collapse icons
 */
@Component({
  imports: [
    FormsModule, TreeViewModule
  ],
  standalone: true,
  selector: 'app-container',
  template: `<div id='treeparent'><ejs-treeview id='treeElement' #treevalidate [fields]='field' (created)='onCreate($event)'></ejs-treeview></div>`
})

export class AppComponent {
  // Data source for TreeView component
  public countries: Object[] = [
    { id: 1, name: 'India', hasChild: true },
    { id: 2, pid: 1, name: 'Assam' },
    { id: 3, pid: 1, name: 'Bihar' },
    { id: 4, pid: 1, name: 'Tamil Nadu' },
    { id: 6, pid: 1, name: 'Punjab' },
    { id: 7, name: 'Brazil', hasChild: true },
    { id: 8, pid: 7, name: 'Paraná' },
    { id: 9, pid: 7, name: 'Ceará' },
    { id: 10, pid: 7, name: 'Acre' },
    { id: 11, name: 'France', hasChild: true },
    { id: 12, pid: 11, name: 'Pays de la Loire' },
    { id: 13, pid: 11, name: 'Aquitaine' },
    { id: 14, pid: 11, name: 'Brittany' },
    { id: 15, pid: 11, name: 'Lorraine' },
    { id: 16, name: 'Australia', hasChild: true },
    { id: 17, pid: 16, name: 'New South Wales' },
    { id: 18, pid: 16, name: 'Victoria' },
    { id: 19, pid: 16, name: 'South Australia' },
    { id: 20, pid: 16, name: 'Western Australia' },
    { id: 21, name: 'China', hasChild: true },
    { id: 22, pid: 21, name: 'Guangzhou' },
    { id: 23, pid: 21, name: 'Shanghai' },
    { id: 24, pid: 21, name: 'Beijing' },
    { id: 25, pid: 21, name: 'Shantou' }
  ];
  public field: Object = { dataSource: this.countries, id: 'id', text: 'name', parentID: 'pid', hasChildren: 'hasChild' };

  @ViewChild('treevalidate') tree?: TreeViewComponent;

  public onCreate(args: any): void {
    let collapse: NodeListOf<Element> = (this.tree as any)?.element.querySelectorAll('.e-icons.e-icon-collapsible') as NodeListOf<Element>;
    let expand: NodeListOf<Element> = (this.tree as any)?.element.querySelectorAll('.e-icons.e-icon-expandable') as NodeListOf<Element>;
    this.hideIcon(expand, collapse);
    (this.tree as any)?.element.addEventListener('mouseenter', (event: any) => {
      this.showIcon(expand, collapse);
    });
    (this.tree as any)?.element.addEventListener('mouseleave', (event: any) => {
      this.hideIcon(expand, collapse);
    });
  }
  // hides expand/collapse icon on hovering the mouse
  public hideIcon(expand: NodeListOf<Element>, collapse: NodeListOf<Element>) {
    for (let i: number = 0; i < collapse.length; i++) {
      collapse[i].setAttribute('style', 'visibility: hidden');
    }
    for (let j: number = 0; j < expand.length; j++) {
      expand[j].setAttribute('style', 'visibility: hidden');
    }
  }

  // shows expand/collapse icon while leaving the mouse
  public showIcon(expand: NodeListOf<Element>, collapse: NodeListOf<Element>) {
    for (let i: number = 0; i < collapse.length; i++) {
      collapse[i].setAttribute('style', "visibility");
    }
    for (let j: number = 0; j < expand.length; j++) {
      expand[j].setAttribute('style', "visibility");
    }
  }
}

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';

#treeparent {
    display: block;
    max-width: 350px;
    max-height: 350px;
    margin: auto;
    overflow: auto;
    border: 1px solid #dddddd;
    border-radius: 3px;
}

main.ts

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