Widget

The base class for widgets. Each widget's presentation is separate from its properties, methods, and data.

The separation of core logic and presentation makes each widget highly customizable when working with other frameworks and libraries such as Bootstrap, React, and JQuery.

The properties and methods of each widget are handled in its viewModel property, which is an Accessor-based class. Since each view model class extends Accessor, all properties on the widget can be accessed using the methods outlined in the Working with properties topic.

This design allows developers to create new widgets and repurpose existing widgets with a third party framework. Separation of a widget's presentation and core logic also means developers can use the logic without having to render its UI components. More information about creating custom widgets is available in the Widget development Guide topic.

See also

Property Overview

Any properties can be set, retrieved or listened to. See the Working with Properties topic.

Show inherited properties

Hide inherited properties

Type	Summary	Class
String\|HTMLElement	The ID or node representing the DOM element containing the widget. more details	Widget
String	The name of the class. more details	Accessor
String	The unique ID assigned to the widget when the widget is created. more details	Widget
String	The widget's label. more details	Widget
Boolean	Indicates whether the widget is visible. more details	Widget

Property Details

container String|HTMLElement

The ID or node representing the DOM element containing the widget. This property can only be set once. The following examples are all valid use cases when working with widgets.

Examples

// Create the HTML div element programmatically at runtime and set to the widget's container
const basemapGallery = new BasemapGallery({
  view: view,
  container: document.createElement("div")
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// Specify an already-defined HTML div element in the widget's container

const basemapGallery = new BasemapGallery({
  view: view,
  container: basemapGalleryDiv
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

// HTML markup
<body>
  <div id="viewDiv"></div>
  <div id="basemapGalleryDiv"></div>
</body>

// Specify the widget while adding to the view's UI
const basemapGallery = new BasemapGallery({
  view: view
});

// Add the widget to the top-right corner of the view
view.ui.add(basemapGallery, {
  position: "top-right"
});

declaredClass Stringreadonly inherited Since: ArcGIS API for JavaScript 4.7

The name of the class. The declared class name is formatted as esri.folder.className.

id String

The unique ID assigned to the widget when the widget is created. If not set by the developer, it will default to the container ID, or if that is not present then it will be automatically generated.

label String Since: ArcGIS API for JavaScript 4.11

The widget's label.

This property is useful whenever the widget is controlled by another one (e.g. Expand)

visible Boolean

Indicates whether the widget is visible.

If false, the widget will no longer be rendered in the web document. This may affect the layout of other elements or widgets in the document. For example, if this widget is the first of three widgets associated to the upper right hand corner of the view UI, then the other widgets will reposition when this widget is made invisible. For more information, refer to the CSS display value of "none".

Default Value:true

Example

// Hides the widget in the view
widget.visible = false;

Method Overview

Show inherited methods

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Return Type	Summary	Class
	Adds one or more handles which are to be tied to the lifecycle of the object. more details	Accessor
String	A utility method used for building the value for a widget's `class` property. more details	Widget
	Destroys the widget instance. more details	Widget
Boolean	Emits an event on the instance. more details	Widget
Boolean	Indicates whether there is an event listener on the instance that matches the provided event name. more details	Widget
Boolean	Returns true if a named group of handles exist. more details	Accessor
Boolean	`isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). more details	Widget
Boolean	`isRejected()` may be used to verify if creating an instance of the class is rejected. more details	Widget
Boolean	`isResolved()` may be used to verify if creating an instance of the class is resolved. more details	Widget
Object	Registers an event handler on the instance. more details	Widget
	Adds one or more handles which are to be tied to the lifecycle of the widget. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Removes a group of handles owned by the object. more details	Accessor
Object	This method is primarily used by developers when implementing custom widgets. more details	Widget
	Renders widget to the DOM immediately. more details	Widget
	This method is primarily used by developers when implementing custom widgets. more details	Widget
Promise	`when()` may be leveraged once an instance of the class is created. more details	Widget

Method Details

addHandles(handleOrHandles, groupKey)inherited Since: ArcGIS API for JavaScript 4.25

Adds one or more handles which are to be tied to the lifecycle of the object. The handles will be removed when the object is destroyed.

// Manually manage handles
const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true }
);

// Handle gets removed when the object is destroyed.
this.addHandles(handle);

Parameters

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the object is destroyed.

groupKey *

optional

Key identifying the group to which the handles should be added. All the handles in the group can later be removed with Accessor.removeHandles(). If no key is provided the handles are added to a default group.

classes(classNames){String} Since: ArcGIS API for JavaScript 4.7

A utility method used for building the value for a widget's class property. This aids in simplifying CSS class setup.

Parameter

classNames String|String []|Object

repeatable

The class names.

Returns

Type	Description
String	The computed class name.

See also

Guide - Widget development (rendering)

Example

// .tsx syntax showing how to set CSS classes while rendering the widget

render() {
  const dynamicIconClasses = {
    [CSS.myIcon]: this.showIcon,
    [CSS.greyIcon]: !this.showIcon
  };

  return (
    <div class={classes(CSS.root, CSS.mixin, dynamicIconClasses)} />
  );
}

destroy()

Destroys the widget instance.

emit(type, event){Boolean} Since: ArcGIS API for JavaScript 4.5

Emits an event on the instance. This method should only be used when creating subclasses of this class.

Parameters

type String

The name of the event.

event Object

optional

The event payload.

Returns

Type	Description
Boolean	`true` if a listener was notified

hasEventListener(type){Boolean}

Indicates whether there is an event listener on the instance that matches the provided event name.

Parameter

type String

The name of the event.

Returns

Type	Description
Boolean	Returns true if the class supports the input event.

hasHandles(groupKey){Boolean}inherited Since: ArcGIS API for JavaScript 4.25

Returns true if a named group of handles exist.

Parameter

groupKey *

optional

A group key.

Returns

Type	Description
Boolean	Returns `true` if a named group of handles exist.

Example

// Remove a named group of handles if they exist.
if (obj.hasHandles("watch-view-updates")) {
  obj.removeHandles("watch-view-updates");
}

isFulfilled(){Boolean} Since: ArcGIS API for JavaScript 4.19

isFulfilled() may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected). If it is fulfilled, true will be returned.

Returns

Type	Description
Boolean	Indicates whether creating an instance of the class has been fulfilled (either resolved or rejected).

isRejected(){Boolean} Since: ArcGIS API for JavaScript 4.19

isRejected() may be used to verify if creating an instance of the class is rejected. If it is rejected, true will be returned.

Returns

Type	Description
Boolean	Indicates whether creating an instance of the class has been rejected.

isResolved(){Boolean} Since: ArcGIS API for JavaScript 4.19

isResolved() may be used to verify if creating an instance of the class is resolved. If it is resolved, true will be returned.

Returns

Type	Description
Boolean	Indicates whether creating an instance of the class has been resolved.

on(type, listener){Object}

Registers an event handler on the instance. Call this method to hook an event with a listener.

Parameters

type String|String []

An event or an array of events to listen for.

listener Function

The function to call when the event fires.

Returns

Type Description

Object

Returns an event handler with a remove() method that should be called to stop listening for the event(s).

Property	Type	Description
remove	Function	When called, removes the listener from the event.

Example

view.on("click", function(event){
  // event is the event handle returned after the event fires.
  console.log(event.mapPoint);
});

own(handleOrHandles) Since: ArcGIS API for JavaScript 4.24

Adds one or more handles which are to be tied to the lifecycle of the widget. The handles will be removed when the widget is destroyed.

const handle = reactiveUtils.when(
  () => !view.updating,
  () => {
    wkidSelect.disabled = false;
  },
  { once: true}
);

this.own(handle); // Handle gets removed when the widget is destroyed.

Parameter

handleOrHandles WatchHandle|WatchHandle []

Handles marked for removal once the widget is destroyed.

postInitialize()

This method is primarily used by developers when implementing custom widgets. Executes after widget is ready for rendering.

removeHandles(groupKey)inherited Since: ArcGIS API for JavaScript 4.25

Removes a group of handles owned by the object.

Parameter

groupKey *

optional

A group key or an array or collection of group keys to remove.

Example

obj.removeHandles(); // removes handles from default group

obj.removeHandles("handle-group");
obj.removeHandles("other-handle-group");

render(){Object}

This method is primarily used by developers when implementing custom widgets. It must be implemented by subclasses for rendering.

Returns

Type	Description
Object	The rendered virtual node.

renderNow()

Renders widget to the DOM immediately.

scheduleRender()

This method is primarily used by developers when implementing custom widgets. Schedules widget rendering. This method is useful for changes affecting the UI.

when(callback, errback){Promise} Since: ArcGIS API for JavaScript 4.19

when() may be leveraged once an instance of the class is created. This method takes two input parameters: a callback function and an errback function. The callback executes when the instance of the class loads. The errback executes if the instance of the class fails to load.

Parameters

callback Function

optional

The function to call when the promise resolves.

errback Function

optional

The function to execute when the promise fails.

Returns

Type	Description
Promise	Returns a new promise for the result of `callback`.

Example

// Although this example uses the BasemapGallery widget, any class instance that is a promise may use when() in the same way
let bmGallery = new BasemapGallery();
bmGallery.when(function(){
  // This function will execute once the promise is resolved
}, function(error){
  // This function will execute if the promise is rejected due to an error
});

ArcGIS API for JavaScriptAPI Reference

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