Q:

Wait until image dowloaded Firebase

I'm loading a recyclerview with Firebase, but sometimes, if there are too many elements, the images take too long to load or they simply don't. 
I'm looking for a way to know when the image has finished downloading (since it happens in the background) and proceed with the code. 
I've wrote what im trying to archieve with some pseudocode, I don't know what is the aproach to take, any answers or info is aprreciated. 
FirebaseStorage storage = FirebaseStorage.getInstance();
    StorageReference storageReference = storage.getReference();
    Glide.with(context)
            .using(new FirebaseImageLoader())
            .load(storageReference.child("users/"+grupo.getUsuario()+"/"+grupo.getTitulo()))
            .into(holder.portada);
  //Here goes what im trying to pursue: a while that wouldn't exit until the image is loaded. 

while(hasnt finished downloading);

A:

Implement a custom target that overrides the onResourceReady or onFailed methods and trigger your custom event handling there.