interface IEventDispatcher
package openfl.events
extended by EventDispatcher
Available on all platforms
The IEventDispatcher interface defines methods for adding or removing event listeners, checks whether specific types of event listeners are registered, and dispatches events.
Event targets are an important part of the OpenFL event model. The event target serves as the focal point for how events flow through the display list hierarchy. When an event such as a mouse click or a keypress occurs, an event object is dispatched into the event flow from the root of the display list. The event object makes a round-trip journey to the event target, which is conceptually divided into three phases: the capture phase includes the journey from the root to the last node before the event target's node; the target phase includes only the event target node; and the bubbling phase includes any subsequent nodes encountered on the return trip to the root of the display list.
In general, the easiest way for a user-defined class to gain event dispatching capabilities is to extend EventDispatcher. If this is impossible (that is, if the class is already extending another class), you can instead implement the IEventDispatcher interface, create an EventDispatcher member, and write simple hooks to route calls into the aggregated EventDispatcher.
See also:
Methods
addEventListener<T>(type:EventType<T>, listener:T ‑> Void, useCapture:Bool = false, priority:Int = 0, useWeakReference:Bool = false):Void
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).
Parameters:
type | The type of event. |
|---|---|
listener | 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: The function can have any name. |
useCapture | Determines whether the listener works in the capture phase or
the target and bubbling phases. If |
priority | 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 |
useWeakReference | 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
|
dispatchEvent(event:Event):Bool
Dispatches an event into the event flow. The event target is the EventDispatcher
object upon which dispatchEvent() is called.
Parameters:
event | The event object dispatched into the event flow. |
|---|
Returns:
A value of true unless preventDefault() is called on the event, in
which case it returns false.
hasEventListener(type:String):Bool
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.
Parameters:
type | The type of event. |
|---|
Returns:
A value of true if a listener of the specified type is registered;
false otherwise.
removeEventListener<T>(type:EventType<T>, listener:T ‑> Void, useCapture:Bool = false):Void
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 | The type of event. |
|---|---|
listener | The listener object to remove. |
useCapture | 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
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willTrigger(type:String):Bool
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 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.
Parameters:
type | The type of event. |
|---|
Returns:
A value of true if a listener of the specified type will be
triggered; false otherwise.