An example of how-to implement an infinite scrolling adapter for a RecyclerView, with a ProgressBar footer. Blog post can be found here: http://msobhy.me/2015/09/05/infinite_scrolling_recyclerview/

AbstractRecyclerViewFooterAdapter.java

package net.sarmady.contactcarswithtabs.adapters;

import android.support.annotation.NonNull;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;

import net.sarmady.contactcarswithtabs.R;
import net.sarmady.contactcarswithtabs.adapters.listener.OnLoadMoreListener;

import java.util.List;

import butterknife.ButterKnife;
import butterknife.InjectView;

/**
 * Created by mSobhy on 7/22/15.
 */
public abstract class AbstractRecyclerViewFooterAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private final int VISIBLE_THRESHOLD = 5;

    private final int ITEM_VIEW_TYPE_BASIC = 0;
    private final int ITEM_VIEW_TYPE_FOOTER = 1;

    private List<T> dataSet;

    private int firstVisibleItem, visibleItemCount, totalItemCount, previousTotal = 0;
    private boolean loading = true;

    public AbstractRecyclerViewFooterAdapter(RecyclerView recyclerView, List<T> dataSet, final OnLoadMoreListener onLoadMoreListener) {
        this.dataSet = dataSet;

        if (recyclerView.getLayoutManager() instanceof LinearLayoutManager) {
            final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
            recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
                @Override
                public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                    totalItemCount = linearLayoutManager.getItemCount();
                    visibleItemCount = linearLayoutManager.getChildCount();
                    firstVisibleItem = linearLayoutManager.findFirstVisibleItemPosition();

                    if (loading) {
                        if (totalItemCount > previousTotal) {
                            loading = false;
                            previousTotal = totalItemCount;
                        }
                    }
                    if (!loading && (totalItemCount - visibleItemCount)
                            <= (firstVisibleItem + VISIBLE_THRESHOLD)) {
                        // End has been reached

                        addItem(null);
                        if (onLoadMoreListener != null) {
                            onLoadMoreListener.onLoadMore();
                        }
                        loading = true;
                    }
                }
            });
        }
    }

    public int getFirstVisibleItem() {
        return firstVisibleItem;
    }

    public void resetItems(@NonNull List<T> newDataSet) {
        loading = true;
        firstVisibleItem = 0;
        visibleItemCount = 0;
        totalItemCount = 0;
        previousTotal = 0;

        dataSet.clear();
        addItems(newDataSet);
    }

    public void addItems(@NonNull List<T> newDataSetItems) {
        dataSet.addAll(newDataSetItems);
        notifyDataSetChanged();
    }

    public void addItem(T item) {
        if (!dataSet.contains(item)) {
            dataSet.add(item);
            notifyItemInserted(dataSet.size() - 1);
        }
    }

    public void removeItem(T item) {
        int indexOfItem = dataSet.indexOf(item);
        if (indexOfItem != -1) {
            this.dataSet.remove(indexOfItem);
            notifyItemRemoved(indexOfItem);
        }
    }

    public T getItem(int index) {
        if (dataSet != null && dataSet.get(index) != null) {
            return dataSet.get(index);
        } else {
            throw new IllegalArgumentException("Item with index " + index + " doesn't exist, dataSet is " + dataSet);
        }
    }

    public List<T> getDataSet() {
        return dataSet;
    }

    @Override
    public int getItemViewType(int position) {
        return dataSet.get(position) != null ? ITEM_VIEW_TYPE_BASIC : ITEM_VIEW_TYPE_FOOTER;
    }

    @Override
    public int getItemCount() {
        return dataSet.size();
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        if (viewType == ITEM_VIEW_TYPE_BASIC) {
            return onCreateBasicItemViewHolder(parent, viewType);
        } else if (viewType == ITEM_VIEW_TYPE_FOOTER) {
            return onCreateFooterViewHolder(parent, viewType);
        } else {
            throw new IllegalStateException("Invalid type, this type ot items " + viewType + " can't be handled");
        }
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder genericHolder, int position) {
        if (getItemViewType(position) == ITEM_VIEW_TYPE_BASIC) {
            onBindBasicItemView(genericHolder, position);
        } else {
            onBindFooterView(genericHolder, position);
        }
    }

    public abstract RecyclerView.ViewHolder onCreateBasicItemViewHolder(ViewGroup parent, int viewType);

    public abstract void onBindBasicItemView(RecyclerView.ViewHolder genericHolder, int position);

    public RecyclerView.ViewHolder onCreateFooterViewHolder(ViewGroup parent, int viewType) {
        //noinspection ConstantConditions
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.progress_bar, parent, false);
        return new ProgressViewHolder(v);
    }

    public void onBindFooterView(RecyclerView.ViewHolder genericHolder, int position) {
        ((ProgressViewHolder) genericHolder).progressBar.setIndeterminate(true);
    }

    public static class ProgressViewHolder extends RecyclerView.ViewHolder {
        @InjectView(R.id.progressBar)
        public ProgressBar progressBar;

        public ProgressViewHolder(View v) {
            super(v);
            ButterKnife.inject(this, v);
        }
    }
}

MyActivity.java

public class MyActivity extends ActionBarActivity {

    @InjectView(R.id.myRecyclerView)
    RecyclerView mRecyclerView;

    RecyclerViewFooterAdapterImpl mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(getLayoutResource());
      
      mRecyclerView.setHasFixedSize(true);

      RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(this);
      mRecyclerView.setLayoutManager(mLayoutManager);

      mAdapter = new RecyclerViewFooterAdapterImpl(mRecyclerView, vehicleModelEngines, new OnLoadMoreListener() {
            @Override
            public void onLoadMore() {
                callEndpointForPage(vehicleMakeModel.getId(), new Runnable() {
                    @Override
                    public void run() {
                        mAdapter.removeItem(null); // don't forget to remove the progress bar representative value
                        updateAdapter(false);
                    }
                });
            }
        }, this, currentSortType);
      mRecyclerView.setAdapter(mAdapter);
    }
    
    private void updateAdapter(boolean shouldGoUp) {
        List<MyModelType> myDataSet = new ArrayList<>(MyModelType);
        mAdapter.resetItems(myDataSet, currentSortType);
        if (shouldGoUp) {
            if (mAdapter.getFirstVisibleItem() <= 50) {
                mRecyclerView.smoothScrollToPosition(0);
            } else {
                mRecyclerView.scrollToPosition(0);
            }
        }
    }
}

progress_bar.xml

<ProgressBar
    android:id="@+id/progressBar"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:padding="@dimen/space_medium"/>

RecyclerViewFooterAdapterImpl.java

package net.sarmady.contactcarswithtabs.adapters;

import android.app.Activity;
import android.content.res.ColorStateList;
import android.graphics.Bitmap;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.engine.DiskCacheStrategy;
import com.bumptech.glide.request.target.BitmapImageViewTarget;

import net.sarmady.contactcarswithtabs.R;
import net.sarmady.contactcarswithtabs.adapters.listener.OnLoadMoreListener;
import net.sarmady.contactcarswithtabs.adapters.view.holders.UsedVehicleModelEngineViewHolder;
import net.sarmady.contactcarswithtabs.entities.UsedVehiclesSortType;
import net.sarmady.contactcarswithtabs.rest.models.CarImage;
import net.sarmady.contactcarswithtabs.rest.models.UsedVehicleEngine;
import net.sarmady.contactcarswithtabs.ui.listeners.VehicleModelEngineClickListener;
import net.sarmady.contactcarswithtabs.utils.DateUtil;
import net.sarmady.contactcarswithtabs.utils.NumberFormatter;

import java.util.List;

/**
 * Created by mSobhy on 7/22/15.
 */
public class RecyclerViewFooterAdapterImpl extends AbstractRecyclerViewFooterAdapter<MyModelType> {

    private Activity activity;
    private SortType currentSortType;

    public RecyclerViewFooterAdapterImpl(RecyclerView recyclerView, List<MyModelType> dataset, OnLoadMoreListener onLoadMoreListener, Activity activity, SortType currentSortType) {
        super(recyclerView, usedVehicleEngines, onLoadMoreListener);
        this.activity = activity;
        this.currentSortType = currentSortType;
    }

    // An wrapper version of resetItems to allow for manipulating Impl adapter data before reseting dataSet
    public void resetItems(@NonNull List<MyModelType> newDataSet, SortType sortType) {
        currentSortType = sortType;
        resetItems(newDataSet);
    }

    @Override
    public RecyclerView.ViewHolder onCreateBasicItemViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.my_normal_item_custom_layout, parent, false);
        return new MyOwnHolder(v);
    }

    @Override
    public void onBindBasicItemView(RecyclerView.ViewHolder genericHolder, int position) {
        final MyOwnHolder holder = (MyOwnHolder) genericHolder;
        final MyModelType currentlySelectedItem = getItem(position);
        // DO YOU BINDING MAGIC HERE
    }
}

totalItemCount = linearLayoutManager.getItemCount();
This line always returned is 0. Why?? Help me please!