[Feature request] Callbacks for data population

I’m probably wrong, but I don’t think the FirebaseRecyclerAdapter and its children have callbacks for when the data is about to be initially populated or when it’s finished populating items. I checked docs and code for the current and 2.0.0 branches, and I didn’t see listeners or callbacks that would allow someone to display a progress bar if the database is taking a lot of time to fetch some items on a slow network and hide it when the items are populated. I know it’s possible to do this for simple references like so:

dataRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        Data data = dataSnapshot.getValue(Data.class);
        textView.setText(data.getText());
        progressBar.setVisibility(View.GONE);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        // ...
    }
});

However, I’m wondering if something like this should be implemented in the FirebaseRecyclerAdapters:

dataAdapter.setOnPopulatedListener(new OnPopulatedListener() {
    @Override
    public void onPopulation() {
        progressBar.setVisibility(View.GONE);
    }
});

// Or perhaps, probably the right choice, by subclassing

public void onInitialPopulation() {
    progressBar.setVisibility(View.GONE);
}

[SUPERCILEX]

@TheCraftKid So many questions! 😄 Well, now #633 should take care of it.

See https://github.com/firebase/FirebaseUI-Android/pull/477#issuecomment-270283875 for when onDataChanged isn’t called.

[WillieCubed]

Why won’t it be supported for the indexing? Is it an implementation issue? Also, in what situations is onDataChanged not called?