How to add pagination in data retreived from FIREBASE STORAGE in android?

Question

I'm trying to add pagination in images data that I'm retrieving from firebase using Firebase Storage. I have 10 images there and I want to display 2 at a time in RecyclerView and when the user scrolls down to end vertically, it loads the next 2 until all the images are displayed, I have also read some documentation of Firebase where it was mentioned to use storage.list(int max results) method but with that, it only shows the number of results that I pass in the method for instance if I pass 2 it shows 2 images only, and I can't load anymore. I've found one method too on the official documentation i.e below: https://firebase.google.com/docs/storage/android/list-files

public void listAllPaginated(@Nullable String pageToken) {
    FirebaseStorage storage = FirebaseStorage.getInstance();
    StorageReference listRef = storage.getReference().child("files/uid");

    // Fetch the next page of results, using the pageToken if we have one.
    Task<ListResult> listPageTask = pageToken != null
            ? listRef.list(100, pageToken)
            : listRef.list(100);

    listPageTask
            .addOnSuccessListener(new OnSuccessListener<ListResult>() {
                @Override
                public void onSuccess(ListResult listResult) {
                    List<StorageReference> prefixes = listResult.getPrefixes();
                    List<StorageReference> items = listResult.getItems();

                    // Process page of results
                    // ...

                    // Recurse onto next page
                    if (listResult.getPageToken() != null) {
                        listAllPaginated(listResult.getPageToken());
                    }
                }
            }).addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    // Uh-oh, an error occurred.
                }
            });
}

I'm confused about how to use it, I don't know where I can get a page token from in order to provide a reference to open the next page

Answer 1

The thing is I have 200 images in my Firebase Storage and I directly want to apply pagination to the URLs that I'm retrieving from Firebase Storage.

To achieve that, you have two options. The first one would be to use StorageReference#listAll() method which:

List all items (files) and prefixes (folders) under this StorageReference.

And according to the official documentation regarding how to list files with Cloud Storage on Android, please note that:

Cloud Storage for Firebase allows you to list the contents of your Cloud Storage bucket. The SDKs return both the items and the prefixes of objects under the current Cloud Storage reference:

So you have to explicitly differentiate that (items vs. prefixes) in your application code and provide your own pagination algorithm.

The second option that you have, and the simplest one, in my opinion, would be to store the image URLs in the Firestore and implement the pagination as explained here:

Paginate data with query cursors