Question

I have a GWT application that uses RPC calls heavily. I would like to display a spinner icon whenever a call is in progress. It is easy enough to display the icon, but I want to do it seamlessly in one place so I don t have to explicitly hide and show the icon for each call.

I guess I am looking for something similar to jQuery s ajaxStart and ajaxStop events.

Has anyone done something like this before?

Cheers Tin

Answer 1

Why don t you implement this behaviour in a concrete implementation of AsyncCallback and subclass all the AsyncCallbacks from this one. Alternatively you could use a decorator pattern where you use a regular AsyncCallback and decorate it with another one that shows/hides the popup.

Alternatively, if you use a Command Pattern, you could just add these events to your command pattern implementation and you can register a handler that shows/hides a popup every time a request is send/received.

Answer 2

In response to comments that suggest a Decorator is not enough.

abstract class AbstractAsyncCallback <T> implements AsyncCallaback <T>
{
 public AbstractAsyncCallback ()
 {
  Foo.showIcon();
 }

 @Override public void success (T t)
 {
  doSuccess(t);
  Foo.hideIcon();
 }

 @Override public void failure ()
 {
  doFailure();
  Foo.hideIcon();
 }

 public abstract void doSuccess (T t);

 public abstract void doFailure (T t);
};

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