Class: View

ol.View

An ol.View object represents a simple 2D view of the map.

This is the object to act upon to change the center, resolution, and rotation of the map.

The view states

An ol.View is determined by three states: center, resolution, and rotation. Each state has a corresponding getter and setter, e.g. getCenter and setCenter for the center state.

An ol.View has a projection. The projection determines the coordinate system of the center, and its units determine the units of the resolution (projection units per pixel). The default projection is Spherical Mercator (EPSG:3857).

The constraints

setCenter, setResolution and setRotation can be used to change the states of the view. Any value can be passed to the setters. And the value that is passed to a setter will effectively be the value set in the view, and returned by the corresponding getter.

But an ol.View object also has a resolution constraint, a rotation constraint and a center constraint.

As said above, no constraints are applied when the setters are used to set new states for the view. Applying constraints is done explicitly through the use of the constrain* functions (constrainResolution and constrainRotation and constrainCenter).

The main users of the constraints are the interactions and the controls. For example, double-clicking on the map changes the view to the "next" resolution. And releasing the fingers after pinch-zooming snaps to the closest resolution (with an animation).

The resolution constraint snaps to specific resolutions. It is determined by the following options: resolutions, maxResolution, maxZoom, and zoomFactor. If resolutions is set, the other three options are ignored. See documentation for each option for more information.

The rotation constraint snaps to specific angles. It is determined by the following options: enableRotation and constrainRotation. By default the rotation value is snapped to zero when approaching the horizontal.

The center constraint is determined by the extent option. By default the center is not constrained at all.

new ol.View(opt_options)

src/ol/view.js, line 100
Name Type Description
options

View options.

Name Type Description
center ol.Coordinate | undefined

The initial center for the view. The coordinate system for the center is specified with the projection option. Default is undefined, and layer sources will not be fetched if this is not set.

constrainRotation boolean | number | undefined experimental

Rotation constraint. false means no constraint. true means no constraint, but snap to zero near zero. A number constrains the rotation to that number of values. For example, 4 will constrain the rotation to 0, 90, 180, and 270 degrees. The default is true.

enableRotation boolean | undefined experimental

Enable rotation. Default is true. If false a rotation constraint that always sets the rotation to zero is used. The constrainRotation option has no effect if enableRotation is false.

extent ol.Extent | undefined experimental

The extent that constrains the center, in other words, center cannot be set outside this extent. Default is undefined.

maxResolution number | undefined

The maximum resolution used to determine the resolution constraint. It is used together with minResolution (or maxZoom) and zoomFactor. If unspecified it is calculated in such a way that the projection's validity extent fits in a 256x256 px tile. If the projection is Spherical Mercator (the default) then maxResolution defaults to 40075016.68557849 / 256 = 156543.03392804097.

minResolution number | undefined

The minimum resolution used to determine the resolution constraint. It is used together with maxResolution (or minZoom) and zoomFactor. If unspecified it is calculated assuming 29 zoom levels (with a factor of 2). If the projection is Spherical Mercator (the default) then minResolution defaults to 40075016.68557849 / 256 / Math.pow(2, 28) = 0.0005831682455839253.

maxZoom number | undefined

The maximum zoom level used to determine the resolution constraint. It is used together with minZoom (or maxResolution) and zoomFactor. Default is 28. Note that if minResolution is also provided, it is given precedence over maxZoom.

minZoom number | undefined

The minimum zoom level used to determine the resolution constraint. It is used together with maxZoom (or minResolution) and zoomFactor. Default is 0. Note that if maxResolution is also provided, it is given precedence over minZoom.

projection ol.proj.ProjectionLike

The projection. Default is EPSG:3857 (Spherical Mercator).

resolution number | undefined

The initial resolution for the view. The units are projection units per pixel (e.g. meters per pixel). An alternative to setting this is to set zoom. Default is undefined, and layer sources will not be fetched if neither this nor zoom are defined.

resolutions Array.<number> | undefined

Resolutions to determine the resolution constraint. If set the maxResolution, minResolution, minZoom, maxZoom, and zoomFactor options are ignored.

rotation number | undefined

The initial rotation for the view in radians (positive rotation clockwise). Default is 0.

zoom number | undefined

Only used if resolution is not defined. Zoom level used to calculate the initial resolution for the view. The initial resolution is determined using the ol.View#constrainResolution method.

zoomFactor number | undefined

The zoom factor used to determine the resolution constraint. Default is 2.

Fires:

Subclasses

Extends

Observable Properties

Name Type Settable ol.ObjectEvent type Description
center ol.Coordinate | undefined yes change:center

The center of the view.

resolution number | undefined yes change:resolution

The resolution of the view.

rotation number yes change:rotation

The rotation of the view in radians.

Methods

calculateExtent(size){ol.Extent}

src/ol/view.js, line 275

Calculate the extent for the current view state and the passed size. The size is the pixel dimensions of the box into which the calculated extent should fit. In most cases you want to get the extent of the entire map, that is map.getSize().

Name Type Description
size ol.Size

Box pixel size.

Returns:
Extent.

centerOn(coordinate, size, position) experimental

src/ol/view.js, line 535

Center on coordinate and view position.

Name Type Description
coordinate ol.Coordinate

Coordinate.

size ol.Size

Box pixel size.

position ol.Pixel

Position on the view to center on.

changed() inherited experimental

src/ol/observable.js, line 52

Increases the revision counter and dispatches a 'change' event.

Fires:
  • change experimental

constrainCenter(center){ol.Coordinate|undefined} experimental

src/ol/view.js, line 212

Get the constrained center of this view.

Name Type Description
center ol.Coordinate | undefined

Center.

Returns:
Constrained center.

constrainResolution(resolution, opt_delta, opt_direction){number|undefined} experimental

src/ol/view.js, line 225

Get the constrained resolution of this view.

Name Type Description
resolution number | undefined

Resolution.

delta number

Delta. Default is 0.

direction number

Direction. Default is 0.

Returns:
Constrained resolution.

constrainRotation(rotation, opt_delta){number|undefined} experimental

src/ol/view.js, line 240

Get the constrained rotation of this view.

Name Type Description
rotation number | undefined

Rotation.

delta number

Delta. Default is 0.

Returns:
Constrained rotation.

fitExtent(extent, size) experimental

src/ol/view.js, line 441

Fit the map view to the passed extent and size. The size is pixel dimensions of the box to fit the extent into. In most cases you will want to use the map size, that is map.getSize().

Name Type Description
extent ol.Extent

Extent.

size ol.Size

Box pixel size.

fitGeometry(geometry, size, opt_options) experimental

src/ol/view.js, line 462

Fit the given geometry into the view based on the given map size and border.

Name Type Description
geometry ol.geom.SimpleGeometry

Geometry.

size ol.Size

Box pixel size.

options

Options.

Name Type Description
padding Array.<number> experimental

Padding (in pixels) to be cleared inside the view. Values in the array are top, right, bottom and left padding. Default is [0, 0, 0, 0].

constrainResolution boolean | undefined experimental

Constrain the resolution. Default is true.

nearest boolean | undefined experimental

Get the nearest extent. Default is false.

minResolution number | undefined experimental

Minimum resolution that we zoom to. Default is 0.

maxZoom number | undefined experimental

Maximum zoom level that we zoom to. If minResolution is given, this property is ignored.

get(key){*} inherited

src/ol/object.js, line 150

Gets a value.

Name Type Description
key string

Key name.

Returns:
Value.

getCenter(){ol.Coordinate|undefined}

src/ol/view.js, line 252

Get the view center.

Returns:
The center of the view.

getKeys(){Array.<string>} inherited

src/ol/object.js, line 164

Get a list of object property names.

Returns:
List of property names.

getProjection(){ol.proj.Projection}

src/ol/view.js, line 293

Get the view projection.

Returns:
The projection of the view.

getProperties(){Object.<string, *>} inherited

src/ol/object.js, line 174

Get an object of all property names and values.

Returns:
Object.

getResolution(){number|undefined}

src/ol/view.js, line 304

Get the view resolution.

Returns:
The resolution of the view.

getRevision(){number} inherited experimental

src/ol/observable.js, line 62
Returns:
Revision.

getRotation(){number}

src/ol/view.js, line 357

Get the view rotation.

Returns:
The rotation of the view in radians.

getZoom(){number|undefined}

src/ol/view.js, line 413

Get the current zoom level. Return undefined if the current resolution is undefined or not a "constrained resolution".

Returns:
Zoom.

on(type, listener, opt_this){goog.events.Key} inherited

src/ol/observable.js, line 75

Listen for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

this Object

The object to use as this in listener.

Returns:
Unique key for the listener.

once(type, listener, opt_this){goog.events.Key} inherited

src/ol/observable.js, line 88

Listen once for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

this Object

The object to use as this in listener.

Returns:
Unique key for the listener.

rotate(rotation, opt_anchor)

src/ol/view.js, line 570

Rotate the view around a given coordinate.

Name Type Description
rotation number

New rotation value for the view.

anchor ol.Coordinate

The rotation center.

set(key, value) inherited

src/ol/object.js, line 203

Sets a value.

Name Type Description
key string

Key name.

value *

Value.

setCenter(center)

src/ol/view.js, line 585

Set the center of the current view.

Name Type Description
center ol.Coordinate | undefined

The center of the view.

setProperties(values) inherited

src/ol/object.js, line 216

Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

Name Type Description
values Object.<string, *>

Values.

setResolution(resolution)

src/ol/view.js, line 611

Set the resolution for this view.

Name Type Description
resolution number | undefined

The resolution of the view.

setRotation(rotation)

src/ol/view.js, line 622

Set the rotation for this view.

Name Type Description
rotation number

The rotation of the view in radians.

setZoom(zoom)

src/ol/view.js, line 632

Zoom to a specific zoom level.

Name Type Description
zoom number

Zoom level.

un(type, listener, opt_this) inherited

src/ol/observable.js, line 101

Unlisten for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.

listener function

The listener function.

this Object

The object which was used as this by the listener.

unByKey(key) inherited

src/ol/observable.js, line 114

Removes an event listener using the key returned by on() or once(). Note that using the ol.Observable.unByKey static function is to be preferred.

Name Type Description
key goog.events.Key

The key returned by on() or once().

unset(key) inherited

src/ol/object.js, line 229

Unsets a property.

Name Type Description
key string

Key name.