Why is the getAssociatedType() method on ValueChangeEvent considered
final? I'd like to be able to extend this event, but I can't extend it
if I can't override getAssociatedType().
Let me explain:
I'm writing a module that is designed to be a base for a slew of other
"expanded" versions of the module, keeping much of the core
functionality locked up in a core module and expanding as necessary
through additional modules.
To be specific, this is a video player module, so some core events
might be PlayEvent or ValueChangeEvent when the currently playing URL
changes. Those events should always be generated by the core, but add-
on modules should be able to respond to those events.
In order to prevent the add-on modules and core components from
needing to know about each other and adding ***Handlers to all the
various Has***Handlers in the application, I created a central
Dispatcher that can register and fire any events - a sort of global
event bus for all events to come in and get dispatched from.
It works well, but because ValueChangeEvent is generic, I can only
implement HasValueChangeHandlers for one type on my central
dispatcher. As it turns out, I need at least two types, and Handlers
are only interested in one or the other.
To register for the right event, I coded this:
private static Map<Integer, Object> TYPES = new HashMap<Integer,
Object>();
@SuppressWarnings("unchecked")
public static <T> Type<ModelHandler<T>> getType(Class<T> clazz) {
Integer key = clazz.hashCode();
if (!ModelChangeEvent.TYPES.containsKey(key)) {
Type<ModelHandler<T>> type = new
Type<ModelHandler<T>>();
ModelChangeEvent.TYPES.put(key, type);
}
return (Type<ModelHandler<T>>) ModelChangeEvent.TYPES.get(key);
}
So you can register for ValueChangeEvents pertaining to a given class
type.
However, I need to override getAssociatedType() to do the following:
@SuppressWarnings("unchecked")
@Override
public Type<ValueChangeHandler<T>> getAssociatedType() {
// TODO: Add null check
Integer key = getValue().getClass().hashCode();
return (Type<ValueChangeHandler<T>>) ModelChangeEvent.TYPES.get
(key);
}
So this limits my ability to reuse the ValueChangeHandler on a more
"global" scope without copy/pasting the class... Unless I am just
completely distorting the point of the new 1.6 event system...
Help?
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