How to show progress dialog until the data loads in FirestoreRecyclerAdapter

问题

I am using FirestoreRecyclerAdapter to load the data from Firestore into RecyclerView. I would like to show progress dialog until the data loads completely. How do I do that? Thanks in advance.

Here is my code so far.

void loadPosts() {
    FirestoreRecyclerOptions<Post> options = new FirestoreRecyclerOptions.Builder<Post>()
            .setQuery(query, Post.class)
            .build();

    adapter = new FirestoreRecyclerAdapter<Post, DataViewHolder>(options) {
        @Override
        protected void onBindViewHolder(@NonNull DataViewHolder dataViewHolder, int i, @NonNull Post post) {
            dataViewHolder.setData(post.getTitle(), post.getDescription());
        }

        @NonNull
        @Override
        public DataViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_post, parent, false);
            return new DataViewHolder(view);
        }
    };
    recyclerView.setAdapter(adapter);
    adapter.startListening();
}

@Override
protected void onStop() {
    super.onStop();
    if (adapter != null) {
        adapter.stopListening();
    }
}

@Override
protected void onStart() {
    super.onStart();
    if (adapter != null) {
        adapter.startListening();
    }
}

回答1:

Before .setQuery(query) in your FirebaseRecyclerAdapter builder you can attach a listener to that query to know when it has completed in order to build the RecyclerView

Example

    progressDialog.show();
    Query query = db.collection("Users").child(my_user_id).addListenerForSingleValue(new ValueEventListener() {
      @Override
      public void onDataChange(DataSnapshot dataSnapshot) {
        //Data has been fetched, hide progressDialog , check if data exists at the location with if(dataSnapshot.exists()) if you want to be sure theres something to fetch
        progressDialog.hide();
      }

      @Override
      public void onCancelled(DatabaseError databaseError) {
        //The fetch failed, dismiss the dialog and show an error message
        progressDialog.hide();
      }
    });

Check the methods of Query

回答2:

While Gastón's answer works, there is a slightly simpler way, that doesn't require an extra listener. The FirestoreRecyclerAdapter has a method that signals when it has received a complete QuerySnapshot.

void loadPosts() {
    FirestoreRecyclerOptions<Post> options = new FirestoreRecyclerOptions.Builder<Post>()
            .setQuery(query, Post.class)
            .build();

    progressDialog.show();

    adapter = new FirestoreRecyclerAdapter<Post, DataViewHolder>(options) {
        @Override
        public void onDataChanged() {
            progressDialog.hide();
        }

        @Override
        protected void onBindViewHolder(@NonNull DataViewHolder dataViewHolder, int i, @NonNull Post post) {
            dataViewHolder.setData(post.getTitle(), post.getDescription());
        }

        @NonNull
        @Override
        public DataViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_post, parent, false);
            return new DataViewHolder(view);
        }
    };
    recyclerView.setAdapter(adapter);
    adapter.startListening();
}

Also see the FirebaseUI documentation on FirestoreRecyclerAdapter data and error events.

Note that onDataChanged may be called multiple times, once initially and then each time when the data for query changes. So make sure that the code in there can handle being called multiple times. For example: if you destroy the progress dialog in onDataChanged instead of hiding it, you'll want to check for its existence too.

来源：https://stackoverflow.com/questions/60475056/how-to-show-progress-dialog-until-the-data-loads-in-firestorerecycleradapter

标签

android

firebase

android-recyclerview

google-cloud-firestore

firebaseui