ScaleBar

The ScaleBar widget displays a scale bar on the map or in a specified HTML node. The widget respects various coordinate systems and displays units in metric or non-metric values. Metric values shows either kilometers or meters depending on the scale, and likewise non-metric values shows miles and feet depending on the scale. When working with Web Mercator or geographic coordinate systems the scale bar takes into account projection distortion and dynamically adjusts the scale bar. The ScaleBar widget sample, which uses a map that has the Web Mercator projection, shows this behavior. Open the sample and note that as you pan the map south towards the equator the scale bar gets shorter and as you pan north it gets longer.

When the scale bar is inside the map, the actual location of the scale bar is used to calculate the scale. Otherwise, the center of the map is used to calculate the scale.

Known Limitations

ScaleBar only works with MapView.

For information about gaining full control of widget styles, see the Styling topic.

See also:

Example:

let scaleBar = new ScaleBar({
  view: view
});
// Add widget to the bottom left corner of the view
view.ui.add(scaleBar, {
  position: "bottom-left"
});

Constructors

new ScaleBar(properties)

Parameter:

properties Object

optional

See the properties for a list of all the properties that may be passed into the constructor.

Example:

// typical usage
let scalebar = new ScaleBar({
  view: view
});

Property Overview

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

Show inherited properties

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Type	Summary	Class
String\|HTMLElement	more details The ID or node representing the DOM element containing the widget.	more details	Widget
String	more details The name of the class.	more details	Accessor
String	more details The unique ID assigned to the widget when the widget is created.	more details	Widget
String	more details The widget's default label.	more details	ScaleBar
String	more details The style for the scale bar.	more details	ScaleBar
String	more details Units to use for the scale bar.	more details	ScaleBar
MapView	more details A reference to the MapView.	more details	ScaleBar
ScaleBarViewModel	more details The view model for this widget.	more details	ScaleBar
Boolean	more details Indicates whether the widget is visible.	more details	Widget

Property Details

container String|HTMLElement inherited

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 inherited

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

The widget's default label.

style String

The style for the scale bar. When unit is set to dual, the style will always be line.

Possible Values:"ruler"|"line"

unit String

Units to use for the scale bar. When using dual, the scale bar displays both metric and non-metric units. Metric values show either kilometers or meters depending on the scale, and non-metric values show either miles or feet depending on the scale.

Possible Values:"non-metric"|"metric"|"dual"

Default Value:non-metric

view MapView

A reference to the MapView. Set this to link the widget to a specific view.

viewModel ScaleBarViewModelautocast

The view model for this widget. This is a class that contains all the logic (properties and methods) that controls this widget's behavior. See the ScaleBarViewModel class to access all properties and methods on the widget.

visible Boolean inherited

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
String	more details A utility method used for building the value for a widget's `class` property.	more details	Widget
	more details Destroys the widget instance.	more details	Widget
Boolean	more details Emits an event on the instance.	more details	Widget
Boolean	more details Indicates whether there is an event listener on the instance that matches the provided event name.	more details	Widget
Boolean	more details `isFulfilled()` may be used to verify if creating an instance of the class is fulfilled (either resolved or rejected).	more details	Widget
Boolean	more details `isRejected()` may be used to verify if creating an instance of the class is rejected.	more details	Widget
Boolean	more details `isResolved()` may be used to verify if creating an instance of the class is resolved.	more details	Widget
Object	more details Registers an event handler on the instance.	more details	Widget
	more details Widget teardown helper.	more details	Widget
	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
Object	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
	more details Renders widget to the DOM immediately.	more details	Widget
	more details This method is primarily used by developers when implementing custom widgets.	more details	Widget
Promise	more details `when()` may be leveraged once an instance of the class is created.	more details	Widget

Method Details

classes(classNames){String}inherited 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()inherited

Destroys the widget instance.

emit(type, event){Boolean}inherited 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}inherited

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.

isFulfilled(){Boolean}inherited 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}inherited 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}inherited 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}inherited

Registers an event handler on the instance. Call this method to hook an event with a listener. See the Events summary table for a list of supported events.

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(handles)inherited

Widget teardown helper. Any handles added to it will be automatically removed when the widget is destroyed.

Parameter:

handles WatchHandle|WatchHandle []

Handles marked for removal once the widget is destroyed.

postInitialize()inherited

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

render(){Object}inherited

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()inherited

Renders widget to the DOM immediately.

scheduleRender()inherited

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}inherited 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` that may be used to chain additional functions.

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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