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
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. 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.
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.
If the event listener is being registered on a node while an event is
being processed on this node, the event listener is not triggered during
the current phase but can 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
registered again for future processing).
Parameters:
type | The type of event. |
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useCapture | 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. |
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priority | 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. |
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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
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.
Weak references are supported on some OpenFL
targets only, including html5, cpp, and
flash/air. On other targets, this parameter is
ignored, and the reference will be strong instead. |
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Throws:
ArgumentError | The listener specified is not a
function. |
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