[FIXED] How to get document id in In FirestorePagingAdapter?

Issue

I am trying to use the FirestorePagingAdapter to display a list of all users in my firestore database. I am using FirestorePagingAdapter instead of FirestoreRecyclerAdapter to minimize the number of reads as FirestorePagingAdapterdoesn't read the whole list of documents while FirestoreRecyclerAdapter does. I am able to display the paginated list successfully but I need to implement onClickListener onto it and on click of every item, I need to open another activity which shows a detailed description of the particular user which was clicked. For this, I need to pass the documentId of the clicked user to the next activity.

But unfortunately, FirestorePagingAdapter doesn't have getSnapshots() method so that I use getSnapshots().getSnapshot(position).getId().

On the other hand, FirestoreRecyclerAdapter has this method which makes fetching the document id a very easy task. Something like this: How to get document id or name in Android in Firestore db for passing on to another activity?

// Query to fetch documents from user collection ordered by name
Query query = FirebaseFirestore.getInstance().collection("users")
                .orderBy("name");

// Setting the pagination configuration
PagedList.Config config = new PagedList.Config.Builder()
                .setEnablePlaceholders(false)
                .setPrefetchDistance(10)
                .setPageSize(20)
                .build();


FirestorePagingOptions<User> firestorePagingOptions = new FirestorePagingOptions.Builder<User>()
                .setLifecycleOwner(this)
                .setQuery(query, config, User.class)
                .build();

firestorePagingAdapter =
                new FirestorePagingAdapter<User, UserViewHolder>(firestorePagingOptions){

                    @NonNull
                    @Override
                    public UserViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                        View view = LayoutInflater.from(parent.getContext())
                                .inflate(R.layout.single_user_layout, parent, false);

                        return new UserViewHolder(view);
                    }

                    @Override
                    protected void onBindViewHolder(@NonNull UserViewHolder holder, int position, @NonNull User user) {
                        holder.setUserName(user.name);
                        holder.setStatus(user.status);
                        holder.setThumbImage(user.thumb_image, UsersActivity.this);


                        holder.mView.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                Intent userProfileIntent = new Intent(UsersActivity.this, UserProfileActivity.class);
                                // Need to fetch the user_id to pass it as intent extra
                                // String user_id = getSnapshots().getSnapshot(position).getId();
                                // userProfileIntent.putExtra("user_id", user_id);
                                startActivity(userProfileIntent);
                            }
                        });
                    }
                };

Solution

I was able to do this by using SnapshotParser in setQuery method. Through this, I was able to modify the object which I got from the firestore. The documentSnapshot.getId() method returns the document id.

FirestorePagingOptions<User> firestorePagingOptions = new FirestorePagingOptions.Builder<User>()
                .setLifecycleOwner(this)
                .setQuery(query, config, new SnapshotParser<User>() {
                    @NonNull
                    @Override
                    public User parseSnapshot(@NonNull DocumentSnapshot snapshot) {
                        User user = snapshot.toObject(User.class);
                        user.userId = snapshot.getId();
                        return user;
                    }
                })
                .build();

In the User class, I just added another field "String userId" in the User class. The userId field doesn't exist in my firestore document. In the onClickListener, I can then directly use user.userId to get the document id and send it to other activity.

Answered By - Shubhaw Kumar
Answer Checked By - Willingham (JavaFixing Volunteer)