javafx.event.EventDispatcher Maven / Gradle / Ivy
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package javafx.event;
// PENDING_DOC_REVIEW
/**
* An {@code EventDispatcher} represents an event dispatching and processing
* entity. It is used when an {@code Event} needs to be dispatched to the
* associated {@code EventTarget} through the {@code EventDispatchChain}
* specified by the target. Each {@code EventDispatcher} in the chain can
* influence the event path and the event itself. One {@code EventDispatcher}
* can appear in multiple chains.
*
* The system defines two successive phases of event delivery. The first
* phase is called capturing phase and happens when when an event travels from
* the first element of the {@code EventDispatchChain} associated with the event
* target to its last element. If the event target is part of some hierarchy,
* the direction of the event in this phase usually corresponds with the
* direction from the root element of the hierarchy to the target. The second
* phase is called bubbling phase and happens in the reverse order to the first
* phase. So the event is returning back from the last element of the
* {@code EventDispatchChain} to its first element in this phase. Usually that
* corresponds to the direction from the event target back to the root in the
* event target's hierarchy.
*
* Each {@code EventDispatcher} in an {@code EventDispatchChain} is responsible
* for forwarding the event to the rest of the chain during event dispatching.
* This forwarding happens in the {@code dispatchEvent} method and forms a chain
* of nested calls which allows one {@code EventDispatcher} to see the event
* during both dispatching phases in a single {@code dispatchEvent} call.
*
* Template for {@code dispatchEvent} implementation.
public Event dispatchEvent(Event event, EventDispatchChain tail) {
// capturing phase, can handle / modify / substitute / divert the event
if (notHandledYet) {
// forward the event to the rest of the chain
event = tail.dispatchEvent(event);
if (event != null) {
// bubbling phase, can handle / modify / substitute / divert
// the event
}
}
return notHandledYet ? event : null;
}
* @since JavaFX 2.0
*/
public interface EventDispatcher {
/**
* Dispatches the specified event by this {@code EventDispatcher}. Does
* any required event processing. Both the event and its further path can
* be modified in this method. If the event is not handled / consumed during
* the capturing phase, it should be dispatched to the rest of the chain
* ({@code event = tail.dispatch(event);}).
*
* @param event the event do dispatch
* @param tail the rest of the chain to dispatch event to
* @return the return event or {@code null} if the event has been handled /
* consumed
*/
Event dispatchEvent(Event event, EventDispatchChain tail);
}