Provide a central access point for a group of events.
Listeners can be added with a simple restriction on the event source.
They are only called for events that originate at the specified source.
Event providers can broadcast an event to all interested listeners.
The XEventMultiplexer interface is typically implemented as a singleton
Remove an event listener for the specified event focus.
When the same listener was added for other event foci then
these associations remain unmodified.
Add an event listener that is called only when events are broadcast for the specified
event focus.
Parameter xListener
An empty reference results in an InvalidArgumentException.
One listener may be added more than once for different
event foci. Adding a listener a second time for the same
event focus results in an InvalidArgumentException.
Parameter xEventFocus
An empty reference is a valid value. In this case the
registered listener will be called for every event
broadcast, regardless of its event focus.
The event focus may or may not be the source of the event.
A typical example for an event focus is the XController of
a view. Using an XController restricts events passed to
a listener to events that belong to one view.
Remove an event listener for the specified event focus.
When the same listener was added for other event foci then
these associations remain unmodified.
Parameter xListener
An empty reference results in an InvalidArgumentException.
When the listener is not registered for the given event
focus then an InvalidArgumentException is thrown.
Parameter xEventFocus
The listener is only removed for this event focus.
An empty reference is a valid value.
