Check box in Angular Treeview component

28 Sep 202313 minutes to read

The TreeView component allows you to check more than one node in TreeView without affecting the UI’s appearance by enabling the showCheckBox property. When this property is enabled, checkbox appears before each TreeView node text.

• If one of the child nodes is not in a checked state, then the parent node will be in an intermediate state.

• If all the child nodes are in checked state, then the parent node’s state will also be checked.

• If a parent node is checked, then all the child nodes’ state will also be checked.

By default, the checkbox state of parent and child nodes are dependent on each other. If you need independent checked state, you can achieve it using the autoCheck property.

Using the checkedNodes property, you can set the nodes that need to be checked or get the ID of nodes that are currently checked in the TreeView component.

If you need to prevent the node check action for a particular node, the nodeChecking event can be used which is triggered before the TreeView node is checked/unchecked. The nodeChecked event will be triggered when the TreeView node is checked/unchecked successfully.

In the following example, the showCheckBox property is enabled.

app.component.ts

import { Component, ViewChild } from '@angular/core';
import { TreeViewComponent } from '@syncfusion/ej2-angular-navigations';
import { enableRipple } from '@syncfusion/ej2-base';
enableRipple(true);

@Component({
    selector: 'app-container',
    // specifies the template string for the TreeView component with CheckBox
    template: `<div id='treeparent'><ejs-treeview id='treeelement' [fields]='field' [showCheckBox]='showCheckBox'></ejs-treeview></div>`
})
export class AppComponent {
    @ViewChild('samples')
    public tree?: TreeViewComponent;

    constructor() {
    }
    // defined the array of data
    public countries: Object[] = [
        { id: 1, name: 'Australia', hasChild: true, expanded: true },
        { id: 2, pid: 1, name: 'New South Wales' },
        { id: 3, pid: 1, name: 'Victoria' },
        { id: 4, pid: 1, name: 'South Australia' },
        { id: 6, pid: 1, name: 'Western Australia' },
        { 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: 'China', hasChild: true },
        { id: 12, pid: 11, name: 'Guangzhou' },
        { id: 13, pid: 11, name: 'Shanghai' },
        { id: 14, pid: 11, name: 'Beijing' },
        { id: 15, pid: 11, name: 'Shantou' },
        { id: 16, name: 'France', hasChild: true },
        { id: 17, pid: 16, name: 'Pays de la Loire' },
        { id: 18, pid: 16, name: 'Aquitaine' },
        { id: 19, pid: 16, name: 'Brittany' },
        { id: 20, pid: 16, name: 'Lorraine' },
        { id: 21, name: 'India', hasChild: true },
        { id: 22, pid: 21, name: 'Assam' },
        { id: 23, pid: 21, name: 'Bihar' },
        { id: 24, pid: 21, name: 'Tamil Nadu' },
        { id: 25, pid: 21, name: 'Punjab' }
    ];
    // maps the appropriate column to fields property
    public field: Object = { dataSource: this.countries, id: 'id', parentID: 'pid', text: 'name', hasChildren: 'hasChild' };
    // set the CheckBox to the TreeView
    public showCheckBox: boolean = true;
}

app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule,TreeViewModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }

main.ts

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

import 'zone.js';
enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

Checked nodes

You can get or set the checked nodes in TreeView at initial rendering and dynamically by using the checkedNodes property.
It returns the checked nodes’ ID as an array.

In the following example, the New South Wales and Western Australia nodes are checked at initial rendering.
If any more nodes are checked, the checked nodes’ IDs will be displayed in alert.

app.component.ts

import { Component,ViewChild } from '@angular/core';
import { TreeViewComponent } from '@syncfusion/ej2-angular-navigations';

@Component({
    selector: 'app-container',
    // specifies the template string for the TreeView component with CheckBox
    template: `<div id='treeparent'><ejs-treeview #treeview="" id='treeelement' [fields]='field' [showCheckBox]='showCheckBox' (nodeChecked)='nodeChecked($event)'></ejs-treeview></div>`
})
export class AppComponent {
    constructor() {
    }
    @ViewChild('treeview')
    public tree?: TreeViewComponent;
    // defined the array of data
    public countries: Object[] = [
        { id: 1, name: 'Australia', hasChild: true, expanded: true },
        { id: 2, pid: 1, name: 'New South Wales', isChecked: true },
        { id: 3, pid: 1, name: 'Victoria' },
        { id: 4, pid: 1, name: 'South Australia' },
        { id: 6, pid: 1, name: 'Western Australia', isChecked: true },
        { 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: 'China', hasChild: true },
        { id: 12, pid: 11, name: 'Guangzhou' },
        { id: 13, pid: 11, name: 'Shanghai' },
        { id: 14, pid: 11, name: 'Beijing' },
        { id: 15, pid: 11, name: 'Shantou' },
        { id: 16, name: 'France', hasChild: true },
        { id: 17, pid: 16, name: 'Pays de la Loire' },
        { id: 18, pid: 16, name: 'Aquitaine' },
        { id: 19, pid: 16, name: 'Brittany' },
        { id: 20, pid: 16, name: 'Lorraine' },
        { id: 21, name: 'India', hasChild: true },
        { id: 22, pid: 21, name: 'Assam' },
        { id: 23, pid: 21, name: 'Bihar' },
        { id: 24, pid: 21, name: 'Tamil Nadu' },
        { id: 25, pid: 21, name: 'Punjab' }
    ];
    // maps the appropriate column to fields property
    public field: Object = { dataSource: this.countries, id: 'id', parentID: 'pid', text: 'name', hasChildren: 'hasChild' };
    // set the CheckBox to the TreeView
    public showCheckBox: boolean = true;
    //set the checknodes to the TreeView
    public checkedNodes: string[] = ['2','6'];
    public nodeChecked(args: any): void{
      alert("The checked node's id is: "+this.tree?.checkedNodes);

    }


}

app.module.ts

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { TreeViewModule } from '@syncfusion/ej2-angular-navigations';
/**
 * Module
 */
@NgModule({
    imports: [
        BrowserModule,FormsModule,TreeViewModule
    ],
    declarations: [AppComponent],
    bootstrap: [AppComponent]
})
export class AppModule { }

main.ts

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { enableProdMode } from '@angular/core';
import { AppModule } from './app.module';

import 'zone.js';
enableProdMode();
platformBrowserDynamic().bootstrapModule(AppModule);

See Also

• How to check/uncheck the checkbox on clicking the tree node text

• How to disable the checkboxes alone in the tree nodes

• How to remove the checkbox of the parent node in treeview