OnDemandEventDispatcher

Pacchetto	mx.utils
Classe	public class OnDemandEventDispatcher
Ereditarietà	OnDemandEventDispatcher Object
Implementa	IEventDispatcher
Sottoclassi	AsyncListView, LayoutBase, NumericDataProvider, OverrideBase

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

OnDemandEventDispatcher serves as a base class for classes that dispatch events but expect listeners to be infrequent. When a class extends OnDemandEventDispatcher instead of the standard EventDispatcher, it is trading off a small overhead on every single instance for a slightly larger overhead on only the instances that actually have listeners attached to them.

Proprietà pubbliche

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	Proprietà		Definito da
		constructor : Object Un riferimento all'oggetto classe o alla funzione di costruzione per una determinata istanza di oggetto.	Object

Metodi pubblici

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	Metodo		Definito da
		OnDemandEventDispatcher() Constructor.	OnDemandEventDispatcher
		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.	OnDemandEventDispatcher
		dispatchEvent(event:Event):Boolean Dispatches an event into the event flow.	OnDemandEventDispatcher
		hasEventListener(type:String):Boolean Checks whether the EventDispatcher object has any listeners registered for a specific type of event.	OnDemandEventDispatcher
		hasOwnProperty(name:String):Boolean Indica se per un oggetto è definita una proprietà specifica.	Object
		isPrototypeOf(theClass:Object):Boolean Indica se un'istanza della classe Object si trova nella catena di prototipi dell'oggetto specificato come parametro.	Object
		propertyIsEnumerable(name:String):Boolean Indica se la proprietà specificata esiste ed è enumerabile.	Object
		removeEventListener(type:String, listener:Function, useCapture:Boolean = false):void Removes a listener from the EventDispatcher object.	OnDemandEventDispatcher
		setPropertyIsEnumerable(name:String, isEnum:Boolean = true):void Imposta la disponibilità di una proprietà dinamica per le operazioni cicliche.	Object
		toLocaleString():String Restituisce la rappresentazione in formato stringa di questo oggetto, formattato in base alle convenzioni specifiche per le versioni localizzate.	Object
		toString():String Restituisce la rappresentazione in formato stringa dell'oggetto specificato.	Object
		valueOf():Object Restituisce il valore di base dell'oggetto specificato.	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.	OnDemandEventDispatcher

Descrizione della funzione di costruzione

()

Funzione di costruzione

public function OnDemandEventDispatcher()

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

Constructor.

Descrizione dei metodi

addEventListener

()

metodo

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

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

Registers an event listener object with an EventDispatcher object so that the listener receives notification of an event. You can register event listeners on all nodes in the display list for a specific type of event, phase, and priority.

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 removeEventListener(). Then you can register the listener again with the new priority level.

After the listener is registered, subsequent calls to addEventListener() with a different value for either type or useCapture result in the creation of a separate listener registration. For example, if you first register a listener with useCapture set to true, it listens only during the capture phase. If you call addEventListener() again using the same listener object, but with useCapture set to false, you have two separate listeners: one that listens during the capture phase, and another that listens during the target and bubbling phases.

You cannot register an event listener for only the target phase or the bubbling phase. Those phases are coupled during registration because bubbling applies only to the ancestors of the target node.

When you no longer need an event listener, remove it by calling EventDispatcher.removeEventListener(); otherwise, memory problems might result. Objects with registered event listeners are not automatically removed from memory because the garbage collector does not remove objects that still have references.

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.

If the event listener is being registered on a node while an event is also being processed on this node, the event listener is not triggered during the current phase but may be triggered during a later phase in the event flow, such as the bubbling phase.

If an event listener is removed from a node while an event is being processed on the node, it is still triggered by the current actions. After it is removed, the event listener is never invoked again (unless it is registered again for future processing).

Parametri

	`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, as this example shows: `function(evt:Event):void` The function can have any name.

	`useCapture:Boolean` (default = `false`) — Determines whether the listener works in the capture phase or the target and bubbling phases. If `useCapture` is set to `true`, the listener processes the event only during the capture phase and not in the target or bubbling phase. If `useCapture` is `false`, the listener processes the event only during the target or bubbling phase. To listen for the event in all three phases, call `addEventListener()` twice, once with `useCapture` set to `true`, then again with `useCapture` set to `false`.

	`priority:int` (default = `0`) — The priority level of the event listener. Priorities are designated by a 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 garbge-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.

dispatchEvent

()

metodo

public function dispatchEvent(event:Event):Boolean

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

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

Parametri

event:Event — The event object dispatched into the event flow.

Restituisce

Boolean — A value of true unless preventDefault() is called on the event, in which case it returns false.

hasEventListener

()

metodo

public function hasEventListener(type:String):Boolean

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

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 will actually trigger an event listener, use IEventDispatcher.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.

Parametri

type:String — The type of event.

Restituisce

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

removeEventListener

()

metodo

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

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

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.

Parametri

	`type:String` — The type of event.

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

	`useCapture:Boolean` (default = `false`) — Specifies whether the listener was registered for the capture phase or the target and bubbling phases. If the listener was registered for both the capture phase and the target and bubbling phases, two calls to `removeEventListener()` are required to remove both: one call with `useCapture` set to `true`, and another call with `useCapture` set to `false`.

willTrigger

()

metodo

public function willTrigger(type:String):Boolean

Versione linguaggio:

ActionScript 3.0

Versione prodotto:

Flex 3

Versioni runtime:

Flash Player 9, AIR 1.1

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.

Parametri

type:String — The type of event.

Restituisce

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

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OnDemandEventDispatcher - AS3 Flex

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