On 28 juin, 17:50, Paul Schwarz <[email protected]> wrote:
> Thanks Phil, though what would this look like in this case?
>
> The design of the GwtEvent and TYPE being static is actually very
> powerful in its elegant simplicity. A call to the constructor of
> GwtEvent.Type() actually causes an int to be incremented and this
> becomes the hashCode "ID" of this event type, and hence assigning that
> to final static variable (TYPE) give a sort of mapping architecture
> where GwtEvent implementations are mapped to int IDs and that's how
> the event bus knows which event has been fired.
>
> So I'm interested to know what you mean by passing in the TYPE from
> elsewhere, because you'd have to be careful not to construct two
> GwtEvent.Type()s to represent a given event type. I'm sure you know
> this, but for the benefit of others who may try to fiddle with the
> mechanism and then wonder why their events aren't caught.
I suppose:
public class GenericEvent extends GwtEvent<GenericEvent.Handler> {
public interface Handler extends EventHandler {
void handleEvent(GenericEvent event);
}
private final Type<Handler> type;
public GenericEvent(Type<Handler> type) {
this.type = type;
}
@Override
public Type<Handler> getAssociatedType() {
return type;
}
@Override
protected void dispatch(Handler handler) {
handler.handleEvent(this);
}
}
...
public static final Type<GenericEvent.Handler> MY_EVENT_TYPE = new
Type<GenericEvent.Handler>();
...
eventBus.addHandler(MY_EVENT_TYPE, new Handler() {
public void handleEvent(GenericEvent event) {
...
}
});
...
eventBus.fireEvent(new GenericEvent(MY_EVENT_TYPE));
Sure, there's the risk of defining 2 MY_EVENT_TYPE for the same
"logical" event, but not much more than the risk of defining 2
GwtEvent.
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