Feature Events

There are a few ways of handling events on features, each of which is suited best for specific tasks. For the most part you will be using the ALKMaps.Control.SelectFeature and ALKMaps.Control.FeatureEvent controls for handling these events. Please note that this does not include markers, any attempt to use these controls on a ALKMaps.Layer.Markers layer or ALKMaps.Marker object will not work.

Special Cases

Please note that the FeatureEvent and SelectFeature controls must be deactivated in order to perform certain actions on a layer. For example the control will need to be temporarily deactivated in order to be able to use a layer's setOpacity function. The control must also be deactivated in order to set a layer's z-index.

SelectFeature Control

The ALKMaps.Control.SelectFeature is best suited for actually selecting one or more features on hover, click, or drag box. The default functionality of this control is to simply highlight any selected features using a predetermined style object. You also have ability to use a custom style object for highlighting a feature when it is selected, or you can choose to not highlight the features at all. Another useful feature of this control is an optional set of user defined functions to be called right before a feature is selected, on selection, and on unselection; as well as triggering "beforefeatureselected", "featureselected", and "featureunselected" events respectively.

SelectFeature Parameters

Parameter Type Description/Values
multipleKey String An event modifier ('altKey' or 'shiftKey') that temporarily sets the multiple property to true. Default is null.
toggleKey String An event modifier ('altKey' or 'shiftKey') that temporarily sets the toggle property to true. Default is null.
multiple Boolean Allow selection of multiple geometries. Default is false.
clickout Boolean Unselect features when clicking outside any feature. Default is true.
toggle Boolean Unselect a selected feature on click. Default is false. Only has meaning if hover is false.
hover Boolean Select on mouse over and deselect on mouse out. If true, this ignores clicks and only listens to mouse moves. Default is false.
highlightOnly Boolean If true do not actually select features (that is place them in the layer's selected features array), just highlight them. This property has no effect if hover is false. Defaults to false.
box Boolean Allow feature selection by drawing a box.
onBeforeSelect Function Optional function to be called before a feature is selected. The function should expect to be called with a feature.
onSelect Function Optional function to be called when a feature is selected. The function should expect to be called with a feature.
onUnselect Function Optional function to be called when a feature is unselected. The function should expect to be called with a feature.
scope Object The scope to use with the onBeforeSelect, onSelect, onUnselect callbacks. If null the scope will be this control.
geometryTypes Array(String) To restrict selecting to a limited set of geometry types, send a list of strings corresponding to the geometry class names.
layers Array(ALKMaps.Layer.Vector |
ALKMaps.Layer.VectorMarkers)
The layers this control will work on.
selectStyle Object Hash of styles to be used for feature selection.

Click The Point To Highlight It

FeatureEvent Control

The ALKMaps.Control.FeatureEvent control is very useful for detecting mouse events on a feature and triggering a corressponding event. The FeatureEvent control has a coulple significant advantages over the SelectFeature control. When dealing with multiple layers, it is important to note that the FeatureEvent control gives you the ability to handle these events on a per layer basis by only triggering the event on the layer which the feature is from. Another exciting aspect is the control's ability to filter out specific features by attribute and have the control ignore the rest. This control now also supports right click events on features. The following table outlines the list of supported events for the FeatureEvent control.

Supported Events
Event Description
featureclicked Triggered when a feature is clicked.
featurerightclicked Triggered when a feature is right clicked.
featureclickedout Triggered when there is a click outside of a feature after a "featureclicked" or "featurerightclicked" event has been triggered for that feature. Last stored feature will be returned in the event.
featurerightclickedout Triggered when there is a right click outside of a feature after a "featureclicked" or "featurerightclicked" event has been triggered for that feature. Last stored feature will be returned in the event.
overFeature Triggered when mouse over a feature.
outFeature Triggered when mouse out a feature.

Hover Over The Left Point To Remove It

As you can see in the sample below, the event can be registered to the specific layer preventing features on other layers from interfering. This FeatureEvent in this sample also uses the featureAttributesFilter option so that only features containing the eventDetection attribute with a value of true will trigger the "overFeature" event.