How to Use `addSnapshotListener` and `remove` in a RecyclerView Item\'s `populateViewHolder` Method with a FirebaseFirestore Query?

Using addSnapshotListener and remove in RecyclerView Item's PopulateViewHolder

Question:

How can I use addSnapshotListener and remove in the populateViewHolder method of a RecyclerView item with a FirebaseFirestore query?

FirebaseUI-Android Library Consideration:

The FirebaseRecyclerAdapter from the FirebaseUI-Android library handles data change notifications for RecyclerView. However, this does not support using addSnapshotListener for populating view holders.

Use EventListener and Global Variable:

To use addSnapshotListener in populateViewHolder, follow these steps:

1. Declare a global EventListener variable:

   <code class="java">EventListener<DocumentSnapshot> eventListener;</code>

2. Initialize the listener and add it in populateViewHolder:

   <code class="java">eventListener = new EventListener<DocumentSnapshot>() {
    @Override
    public void onEvent(DocumentSnapshot snapshot, FirebaseFirestoreException e) {
        if (e != null) {
            Log.w(TAG, "Listen failed.", e);
            return;
        }
   
        if (snapshot != null && snapshot.exists()) {
            // Do what you need to do
        }
    }
   };
   if (listenerRegistration == null) {
    listenerRegistration = yourRef.addSnapshotListener(eventListener);
   }</code>

3. Remove the listener in onStop():

   <code class="java">@Override
   protected void onStop() {
    if (listenerRegistration != null) {
        listenerRegistration.remove();
    }
   }</code>

4. Add the listener again in onStart():

   <code class="java">@Override
   protected void onStart() {
    super.onStart();
    if (listenerRegistration == null) {
        listenerRegistration = yourRef.addSnapshotListener(eventListener);
    }
   }</code>

Alternative Options:

• If real-time data updates are not necessary, consider using get(). This reads the document once and does not require listeners.
• You can also manually remove the listener by passing the activity as the first argument to addSnapshotListener. Firestore will then automatically clean up the listener when the activity is stopped.

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