Recycler View Load Next Page / Edit / Delete Records Using MVVM+ROOM

View model has been initialized by the following code inside fragment.

viewModel.getContacts(pageNumber, AppConstants.DIRECTION).observe(getActivity(), list -> {
        adapter.submitList(list);
    });

where viewModel.getContacts() method calls a repository method which in turn makes the web request and brings the response back.

public MutableLiveData<List<Contact>> getAllContacts(int page, String sortedBy) {
    return repository.getAllContacts(page, sortedBy);
}

where repository.getAllContacts() method is

public MutableLiveData<List<Contact>> getAllContacts(int page, String orderBy) {
    if (allContacts == null) {
        allContacts = new MutableLiveData<>();
    }
    //we will load it asynchronously from server in this method
    loadContacts(page, orderBy);

    return allContacts;
}

private void loadContacts(int page, String orderBy) {

    Call<ContactsResponse> call = bearerApiInterface.getContacts(page, orderBy);


    call.enqueue(new Callback<ContactsResponse>() {
        @Override
        public void onResponse(Call<ContactsResponse> call, Response<ContactsResponse> response) {
            Timber.e("Contacts Response => " + new GsonBuilder().setPrettyPrinting().create().toJson(response.body()));
            //finally we are setting the list to our MutableLiveData
            allContacts.setValue(response.body().getResult().getData());
        }

        @Override
        public void onFailure(Call<ContactsResponse> call, Throwable t) {

        }
    });
}

And here is my recycler view scroll listener

 recyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(linearLayoutManager) {
        @Override
        public void onLoadMore(int current_page) {
            loadNextPage();
        }
    });

Upon scrolling, how could i send the next call with viewModel.getContacts() observer.

What are the options to send the call again with incremented page number and observe it with same viewModel.getContacts() method. Paging list adapter is not an option for now as the response needs to be updated, deleted & customized while paging list adapter isn't doing that without datasource and snapshot inclusion which isn't working (any help with that would be very helpful if it is possible).

And below is the code for deleting any item from recycler view.

@Override
public void onItemDelete(RecyclerView.ViewHolder viewHolder, int position) {
    mActivity.showProgressBar(true);
    Timber.e("Delete the contact at position " + position);
    viewModel.deleteContact(adapter.getContactAt(viewHolder.getAdapterPosition()).getId(), adapter.getContactAt(viewHolder.getAdapterPosition())).observe(this, new Observer<Boolean>() {
        @Override
        public void onChanged(Boolean isSuccess) {
            if (isSuccess) {
                mActivity.showErrorDialog("Contact Deleted Successfully", null, null);
                listAdapter.notifyItemRemoved(viewHolder.getAdapterPosition());
            } else {
                mActivity.showErrorDialog("Something went wrong, please try again", null, null);
            }
        }
    });
}

The view model delete method is

public MutableLiveData<Boolean> deleteContact(int id, Contact contact) {
    return repository.deleteThisContact(id, contact);
}

And the repository delete method is

public MutableLiveData<Boolean> deleteThisContact(int contactId, Contact contact) {
    if (deleteContact == null)
        deleteContact = new MutableLiveData<>();
    callDeleteContact(contactId, contact);
    return deleteContact;
}

private void callDeleteContact(int contactId, Contact contact) {
    Call<JsonObject> call = bearerApiInterface.deleteContact(contactId);
    call.enqueue(new Callback<JsonObject>() {
        @Override
        public void onResponse(Call<JsonObject> call, Response<JsonObject> response) {
            if (response.isSuccessful() && response.code() == 200) {
                Timber.e("***** Contact Deleted Successfully => " + new GsonBuilder().setPrettyPrinting().create().toJson(response.body()));
                delete(contact);
                deleteContact.setValue(true);

            } else {
                try {
                    deleteContact.setValue(false);
                    String errorMessage = new APIError().extractMessage(new JSONObject(response.errorBody() != null ? response.errorBody().string().trim() : null));
                    Timber.e("***** Error message is => " + errorMessage);
                } catch (JSONException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

        @Override
        public void onFailure(Call<JsonObject> call, Throwable t) {
            deleteContact.setValue(false);
            Timber.e("***** onFailure" + "response: " + t.getMessage());
        }
    });
}

Any related code which might be worthy of sharing can be asked. Skipped for simplicity.

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