Angular Knob Component

The Knob component for Angular represents a plugin with round shape which displays a draggable indicator within a range of values.

Prerequisites

Refer to Angular Getting Started before you start with this help topic.

Configuration

I. Imports

The Knob component for Angular requires the following imports.

II. @Component Decorator

A class is marked as an Angular component through the @Component decorator:

selector - CSS selector that identifies this component in a template
styles - inline-defined styles to be applied to this component's view
styleUrls - list of URLs to stylesheets to be applied to this component's view
template - inline-defined template for the view
templateUrl - URL to an external file containing a template for the view

The full list of @Component decorator properties is available on: Angular @Component Decorator API

Every jQWidgets Angular component has an [auto-create] attribute which determines whether the component is automatically created or is created on demand by API method call.
By default, the [auto-create] attribute value is true.

III. Create the AppComponent class

The AppComponent class is used to instantiate the app. In some of the examples, we use @ViewChild and ngAfterViewInit.

@ViewChild: makes a reference using a Knob selector. View queries are set before the ngAfterViewInit callback is called.
@ViewChild('knobReference') myKnob: jqxKnobComponent;
ngAfterViewInit - this is an Angular Component Lifecycle method in which we create our angular components. After the view is initialized, myKnob is available.
For more information about this methods please refer to Angular Component Lifecycle API

The following example demonstrates the Knob component for Angular.

app.component.htm

app.component.css

app.component.ts

Run Code

IV. Create Knob component with JSON

Add the imports.
import { Component, ViewChild, AfterViewInit } from '@angular/core';
import { jqxKnobComponent } from 'jqwidgets-ng/jqxknob';
@Component decorator:
```
@Component({
    selector: 'app-root',
    template: `<jqxKnob #knobReference></jqxKnob>`
})
```
Create the AppComponent class.
- @ViewChild: makes a reference using a Knob selector. View queries are set before the ngAfterViewInit callback is called.
```
@ViewChild('knobReference') myKnob: jqxKnobComponent;
```
- ngAfterViewInit: All Angular components have an integrated method called createComponent that accept a JSON object with the component initialization properties. If no argument is passed, default properties will be used. If you would like to dynamically set properties after creation, you can use the setOptions method.
```
ngAfterViewInit(): void
{
    this.myKnob.createComponent(this.KnobSettings);
}
```
The following example demonstrates how to create a Knob component for Angular by using the createComponent method.

Properties

The properties which are defined as attributes can be changed directly:

To get or set a property, which we did not define or call a method, we can do the following:

Import @ViewChild decorator:
Add the Knob component:
Get access to the Knob component and its API:
Finally, we can call methods or set/get properties like that:

Every component has a method setOptions which accepts a JSON object as an argument. This object contains component settings and you can use it to set a single or multiple properties dynamically.

Events

The change event is triggered when the value is changed.

The following example demonstrates how to add an event listener.

Note: Event Names of the Knob component for Angular are the same as the Event Names of the jqxKnob widget.
The only thing you need to do is to put "on" before the event name and upperCase it's the first letter.

Methods

To invoke methods, you can use the Knob reference.
( refresh() to refresh the widget ) - this.myKnob.refresh().

The following example demonstrates how to invoke methods of the Knob component for Angular.

Knob Examples

Overview

The following example demonstrates how to create a Knob component for Angular.

Disabling

The following example demonstrates how to disable the Knob component for Angular.

Knob API

API Reference of the jQWidgets Knob component for Angular: Knob API