If I understand the proposal correctly, this should already work by calling MediaBrowser.subscribe first, which returns onChildrenChanged with the total number of children and then the browser can request the items individually with getChildren(..., pageSize=1,..). Would that work for your use case?

If I understand the proposal correctly, this should already work by calling MediaBrowser.subscribe first, which returns onChildrenChanged with the total number of children and then the browser can request the items individually with getChildren(..., pageSize=1,..). Would that work for your use case?

Thanks. So in this case, when the service doesn't have the data in onChildrenChanged and it will return a ListenableFuture. How will the loading progress (like % downloaded) be relayed to the client?

onChildrenChanged will just notify about the number of items, which should ideally be quick. And the the MediaBrowser can do something like:

public void onChildrenChanged(..., int ItemCount,...) {
  AtomicInteger loadedItems = new AtomicInteger(0); 
  updateProgressBar(0);
  for (int i = 0; i < itemCount; i  ) {
    ListenableFuture<..> childFuture = getChildren(..., /* page */ i, /* pageSize */ 1, ...);
    Futures.addCallback(childFuture, new FutureCallback<>() {
        public void onSuccess(...) {
           loadedItems  ;
           updateProgressBar(loadedItems / itemCount);
        }

        public void onFailure(...) { }
    });
  }
}

onChildrenChanged will just notify about the number of items, which should ideally be quick. And the the MediaBrowser can do something like:

public void onChildrenChanged(..., int ItemCount,...) {
  AtomicInteger loadedItems = new AtomicInteger(0); 
  updateProgressBar(0);
  for (int i = 0; i < itemCount; i  ) {
    ListenableFuture<..> childFuture = getChildren(..., /* page */ i, /* pageSize */ 1, ...);
    Futures.addCallback(childFuture, new FutureCallback<>() {
        public void onSuccess(...) {
           loadedItems  ;
           updateProgressBar(loadedItems / itemCount);
        }

        public void onFailure(...) { }
    });
  }
}

In our case, the total number of items isn't known in advance and determining that itself takes a while from the service end.

In our case, the total number of items isn't known in advance and determining that itself takes a while from the service end.

In this case I can only recommend sending sendCustomCommand, as you already pointed out yourself. Do you have another API in mind that would you would really like to see in the library? I can't really see a good way to fit your feature request into the existing APIs, so I'm curious if you already had something in mind.

In our case, the total number of items isn't known in advance and determining that itself takes a while from the service end.

In this case I can only recommend sending sendCustomCommand, as you already pointed out yourself. Do you have another API in mind that would you would really like to see in the library? I can't really see a good way to fit your feature request into the existing APIs, so I'm curious if you already had something in mind.

On top of my head, APIs could leverage the existing notify pattern from service end, notifyLoading(Bundle), notifyError(Bundle) and clients could have callbacks similar to onChildrenChanged.

Thanks, in this case sending a custom message is probably most useful still because the requirements for such a loading callback may be quite different between apps. I can only imagine that having a dedicated method makes sense when where is a generic controller that can display the progress from all apps. The proposed notifyLoading(bundle) method is very similar to sendCustomCommand(progressCommand, bundle) in your code in the end as well.

In the interest of providing a reactive interface, you may also want to publish a small number of items initially, and then later call notifyChildrenChanged once your backend has loaded more items.