How to handle pagination in retrofit

Question

I\'m building an app using retrofit. Everything\'s working swimmingly, but I\'m worried about the size of my API requests and would like to split them up using pagination.

Answer 1

So I ended up solving my problem like this:

I am using Grape on my server, so I installed the Grape-kaminari gem to handle the pagination server-side. Grape-kaminari provides a page query on your urls, and adds handy paging information to the header response.

I wrote a small class to allow me to automatically recurse through pages until I've consumed all the data on the API:

package com.farmgeek.agricountantdemo.app.helpers;

import android.util.Log;

import retrofit.client.Header;
import retrofit.client.Response;

public class APIHelper {
    public static PaginationData getPaginationData(Response response) {
        int currentPage = 1;
        int totalPages = 1;
        for (Header header : response.getHeaders()) {
            try {
                    if (header.getName().equals("X-Page")) {
                        currentPage = Integer.parseInt(header.getValue());
                    } else if (header.getName().equals("X-Total-Pages")) {
                        totalPages = Integer.parseInt(header.getValue());
                    }
            } catch (NullPointerException e) {
                // We don't care about header items
                // with empty names, so just skip over
                // them.
                Log.w("APIHelper -> getPaginationData", "Skipped over header: " + e.getLocalizedMessage());
            }
        }
        return new PaginationData(currentPage, totalPages);
    }

    public static class PaginationData {
        public final int page;
        public final int total;

        public PaginationData(int currentPage, int totalPages) {
            this.page = currentPage;
            this.total = totalPages;
        }
    }
}

I'd then use it in my API call like so:

public void getStuff(int page) {
    final RestAdapter restAdapter = buildRestAdapter();

    // Tell the sync adapter something's been added to the queue
    ApiService apiService = restAdapter.create(ApiService.class);
    apiService.getStuff(page, new Callback>() {
        @Override
        public void success(final List stuffList, Response response) {
            final APIHelper.PaginationData pagination = APIHelper.getPaginationData(response);

            for (final Stuff stuff : stuffList) {
                handleRecord(stuff);
            }

            if (pagination.page == pagination.total) {
                App.getEventBus().postSticky(new StuffSyncEvent());
                App.getEventBus().post(new SuccessfulSyncEvent(Stuff.class));
            } else {
                // Otherwise pull down the next page
                new StuffSyncRequestAdapter().getStuff(pagination.page+1);
            }

        }

        @Override
        public void failure(RetrofitError error) {
            String errorMessage = error.getCause().getMessage();
            App.getEventBus().post(new UnsuccessfulSyncEvent(Stuff.class, errorMessage));
        }
    });
}