public interface EventTarget
The
EventTarget
interface is implemented by all
Nodes
in an implementation which supports the DOM Event
Model. Therefore, this interface can be obtained by using
binding-specific casting methods on an instance of the Node
interface. The interface allows registration and removal of
EventListeners
on an EventTarget
and dispatch
of events to that EventTarget
.
See also the Document Object Model (DOM) Level 2 Events Specification.
- Since:
- 1.5, DOM Level 2
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Method Summary
Modifier and TypeMethodDescriptionvoid
addEventListener
(String type, EventListener listener, boolean useCapture) This method allows the registration of event listeners on the event target.boolean
dispatchEvent
(Event evt) This method allows the dispatch of events into the implementations event model.void
removeEventListener
(String type, EventListener listener, boolean useCapture) This method allows the removal of event listeners from the event target.
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Method Details
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addEventListener
This method allows the registration of event listeners on the event target. If anEventListener
is added to anEventTarget
while it is processing an event, it will not be triggered by the current actions but may be triggered during a later stage of event flow, such as the bubbling phase.
If multiple identicalEventListener
s are registered on the sameEventTarget
with the same parameters the duplicate instances are discarded. They do not cause theEventListener
to be called twice and since they are discarded they do not need to be removed with theremoveEventListener
method.- Parameters:
type
- The event type for which the user is registeringlistener
- Thelistener
parameter takes an interface implemented by the user which contains the methods to be called when the event occurs.useCapture
- If true,useCapture
indicates that the user wishes to initiate capture. After initiating capture, all events of the specified type will be dispatched to the registeredEventListener
before being dispatched to anyEventTargets
beneath them in the tree. Events which are bubbling upward through the tree will not trigger anEventListener
designated to use capture.
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removeEventListener
This method allows the removal of event listeners from the event target. If anEventListener
is removed from anEventTarget
while it is processing an event, it will not be triggered by the current actions.EventListener
s can never be invoked after being removed.
CallingremoveEventListener
with arguments which do not identify any currently registeredEventListener
on theEventTarget
has no effect.- Parameters:
type
- Specifies the event type of theEventListener
being removed.listener
- TheEventListener
parameter indicates theEventListener
to be removed.useCapture
- Specifies whether theEventListener
being removed was registered as a capturing listener or not. If a listener was registered twice, one with capture and one without, each must be removed separately. Removal of a capturing listener does not affect a non-capturing version of the same listener, and vice versa.
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dispatchEvent
This method allows the dispatch of events into the implementations event model. Events dispatched in this manner will have the same capturing and bubbling behavior as events dispatched directly by the implementation. The target of the event is theEventTarget
on whichdispatchEvent
is called.- Parameters:
evt
- Specifies the event type, behavior, and contextual information to be used in processing the event.- Returns:
- The return value of
dispatchEvent
indicates whether any of the listeners which handled the event calledpreventDefault
. IfpreventDefault
was called the value is false, else the value is true. - Throws:
EventException
- UNSPECIFIED_EVENT_TYPE_ERR: Raised if theEvent
's type was not specified by initializing the event beforedispatchEvent
was called. Specification of theEvent
's type asnull
or an empty string will also trigger this exception.
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