flash.events.EventDispatcher - Adobe® AIR® API Reference for HTML Developers

window.runtime property	window.runtime.flash.events.EventDispatcher

Inheritance	EventDispatcher Object

Runtime Versions:

AIR 1.0,

The EventDispatcher class is the base class for all runtime classes that dispatch events.

You can register functions to handle runtime events by calling the addEventListener() method of the object dispatching the event.

Properties

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	Property		Defined By
		constructor : Object A reference to the class object or constructor function for a given object instance.	Object
		prototype : Object [static] A reference to the prototype object of a class or function object.	Object

Public Methods

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	Method		Defined By
		EventDispatcher(target:IEventDispatcher = null) Aggregates an instance of the EventDispatcher class.	EventDispatcher
		addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event.	EventDispatcher
		dispatchEvent(event:Event):Boolean Dispatches an event into the event flow.	EventDispatcher
		hasEventListener(type:String):Boolean Checks whether the EventDispatcher object has any listeners registered for a specific type of event.	EventDispatcher
		hasOwnProperty(name:String):Boolean Indicates whether an object has a specified property defined.	Object
		isPrototypeOf(theClass:Object):Boolean Indicates whether an instance of the Object class is in the prototype chain of the object specified as the parameter.	Object
		propertyIsEnumerable(name:String):Boolean Indicates whether the specified property exists and is enumerable.	Object
		removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void Removes a listener from the EventDispatcher object.	EventDispatcher
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Sets the availability of a dynamic property for loop operations.	Object
		toLocaleString():String Returns the string representation of this object, formatted according to locale-specific conventions.	Object
		toString():String Returns the string representation of the specified object.	Object
		valueOf():Object Returns the primitive value of the specified object.	Object
		willTrigger(type:String):Boolean Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type.	EventDispatcher

Events

	Event		Summary	Defined By
		activate	[broadcast event] Dispatched when the Flash Player or AIR application gains operating system focus and becomes active.	EventDispatcher
		deactivate	[broadcast event] Dispatched when the Flash Player or AIR application operating loses system focus and is becoming inactive.	EventDispatcher

Constructor Detail

EventDispatcher

()

Constructor

public function EventDispatcher(target:IEventDispatcher = null)

Runtime Versions:

AIR 1.0,

Aggregates an instance of the EventDispatcher class.

The EventDispatcher class is generally used as a base class in ActionScript 3.0 code used in SWF content, which means that JavaScript developers do not need to use this constructor function.

Parameters

target:IEventDispatcher (default = null) — The target object for events dispatched to the EventDispatcher object. Target objects are only relavent in display objects in SWF content, which use the ActionScript 3.0 display list architecture.

Method Detail

addEventListener

()

method

 public function addEventListener(type:String, listener:Function, useCapture:Boolean = false, priority:int = 0, useWeakReference:Boolean = false):void

Runtime Versions:

AIR 1.0,

Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event.

JavaScript code in the AIR runtime uses this method to register event listeners for events defined by the AIR APIs. For other JavaScript events (such as the onload event of the DOM body object), you can use standard event handling techniques, as you would for content running in the browser.

After you successfully register an event listener, you cannot change its priority through additional calls to addEventListener(). To change a listener's priority, you must first call removeListener(). Then you can register the listener again with the new priority level.

Keep in mind that after the listener is registered, subsequent calls to addEventListener() with a different type or useCapture value result in the creation of a separate listener registration.

If you no longer need an event listener, remove it by calling removeEventListener(), or memory problems could result. Event listeners are not automatically removed from memory because the garbage collector does not remove the listener as long as the dispatching object exists (unless the useWeakReference parameter is set to true).

Copying an EventDispatcher instance does not copy the event listeners attached to it. (If your newly created node needs an event listener, you must attach the listener after creating the node.) However, if you move an EventDispatcher instance, the event listeners attached to it move along with it.

Parameters

	`type:String` — The type of event.

	`listener:Function` — The listener function that processes the event. This function must accept an Event object as its only parameter and must return nothing . The function can have any name.

	`useCapture:Boolean` (default = `false`) — This parameter applies to display objects in the ActionScript 3.0 display list architecture, used by SWF content.

	`priority:int` (default = `0`) — The priority level of the event listener. The priority is designated by a signed 32-bit integer. The higher the number, the higher the priority. All listeners with priority n are processed before listeners of priority n-1. If two or more listeners share the same priority, they are processed in the order in which they were added. The default priority is 0.

	`useWeakReference:Boolean` (default = `false`) — Determines whether the reference to the listener is strong or weak. A strong reference (the default) prevents your listener from being garbage-collected. A weak reference does not. Class-level member functions are not subject to garbage collection, so you can set `useWeakReference` to `true` for class-level member functions without subjecting them to garbage collection. If you set `useWeakReference` to `true` for a listener that is a nested inner function, the function will be garbage-collected and no longer persistent. If you create references to the inner function (save it in another variable) then it is not garbage-collected and stays persistent.

Throws

ArgumentError — The listener specified is not a function.

dispatchEvent

()

method

public function dispatchEvent(event:Event):Boolean

Runtime Versions:

AIR 1.0,

Dispatches an event into the event flow. The event target is the EventDispatcher object upon which the dispatchEvent() method is called.

Parameters

event:Event — The Event object that is dispatched into the event flow. If the event is being redispatched, a clone of the event is created automatically. After an event is dispatched, its target property cannot be changed, so you must create a new copy of the event for redispatching to work.

Returns

Boolean — A value of true if the event was successfully dispatched. A value of false indicates failure or that preventDefault() was called on the event.

Throws

Error — The event dispatch recursion limit has been reached.

hasEventListener

()

method

public function hasEventListener(type:String):Boolean

Runtime Versions:

AIR 1.0,

Checks whether the EventDispatcher object has any listeners registered for a specific type of event. This allows you to determine where an EventDispatcher object has altered handling of an event type in the event flow hierarchy. To determine whether a specific event type actually triggers an event listener, use willTrigger().

The difference between hasEventListener() and willTrigger() is that hasEventListener() examines only the object to which it belongs, whereas willTrigger() examines the entire event flow for the event specified by the type parameter. The event flow applies to the ActionScript 3.0 display list, used in SWF content.

When hasEventListener() is called from a LoaderInfo object, only the listeners that the caller can access are considered.

Parameters

type:String — The type of event.

Returns

Boolean — A value of true if a listener of the specified type is registered; false otherwise.

removeEventListener

()

method

public function removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void

Runtime Versions:

AIR 1.0,

Removes a listener from the EventDispatcher object. If there is no matching listener registered with the EventDispatcher object, a call to this method has no effect.

Parameters

	`type:String` — The type of event.

	`listener:Function` — The listener object to remove.

	`useCapture:Boolean` (default = `false`) — This parameter applies to display objects in the ActionScript 3.0 display list architecture, used by SWF content.

willTrigger

()

method

public function willTrigger(type:String):Boolean

Runtime Versions:

AIR 1.0,

Checks whether an event listener is registered with this EventDispatcher object or any of its ancestors for the specified event type. This method returns true if an event listener is triggered during any phase of the event flow when an event of the specified type is dispatched to this EventDispatcher object or any of its descendants.

The difference between the hasEventListener() and the willTrigger() methods is that hasEventListener() examines only the object to which it belongs, whereas the willTrigger() method examines the entire event flow for the event specified by the type parameter. The event flow applies to the ActionScript 3.0 display list, used in SWF content.

When willTrigger() is called from a LoaderInfo object, only the listeners that the caller can access are considered.

Parameters

type:String — The type of event.

Returns

Boolean — A value of true if a listener of the specified type will be triggered; false otherwise.

Event Detail

activate

Event

Event Object Type: flash.events.Event
property Event.type = flash.events.Event.ACTIVATE

Runtime Versions:

AIR 1.0,

[broadcast event] Dispatched when the AIR application gains operating system focus and becomes active. This event is a broadcast event, which means that it is dispatched by all EventDispatcher objects with a listener registered for this event.

The ACTIVATE constant defines the value of the type property of an activate event object.

Note: This event has neither a "capture phase" nor a "bubble phase", which means that event listeners must be added directly to any potential targets, whether the target is on the display list or not.

AIR for TV devices never automatically dispatch this event. You can, however, dispatch it manually.

This event has the following properties:

Property	Value
`bubbles`	`false`
`cancelable`	`false`; there is no default behavior to cancel.
`currentTarget`	The object that is actively processing the Event object with an event listener.
`target`	Any DisplayObject instance with a listener registered for the `activate` event.

deactivate

Event

Event Object Type: flash.events.Event
property Event.type = flash.events.Event.DEACTIVATE

Runtime Versions:

AIR 1.0,

[broadcast event] Dispatched when the AIR application operating loses system focus and is becoming inactive. This event is a broadcast event, which means that it is dispatched by all EventDispatcher objects with a listener registered for this event.

The Event.DEACTIVATE constant defines the value of the type property of a deactivate event object.

AIR for TV devices never automatically dispatch this event. You can, however, dispatch it manually.

This event has the following properties:

Property	Value
`bubbles`	`false`
`cancelable`	`false`; there is no default behavior to cancel.
`currentTarget`	The object that is actively processing the Event object with an event listener.
`target`	Any DisplayObject instance with a listener registered for the `deactivate` event.

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