PullDown Android detector

PulldownListViewHelper

import android.widget.AbsListView;
import android.widget.ListView;

/**
 * Makes a listview to have a pull down, this is a wrapper.
 * Is not a good idea to override a ListView because there
 * are a lot of libraries and we dont know when we need one.
 */
public class PulldownListViewHelper {

  private final static int ITEMS_BEFORE_LAST_TO_DETECT = 3;

  private ListView listView;
  private OnPullDownListener listener;
  AbsListView.OnScrollListener scrolllistener = new AbsListView.OnScrollListener() {

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount,
        int totalItemCount) {
      final int lastItem = firstVisibleItem + visibleItemCount;
      if (listener != null && lastItem >= (totalItemCount - ITEMS_BEFORE_LAST_TO_DETECT)) {
        listener.onPullDown();
      }
    }
  };

  public PulldownListViewHelper(ListView listView, OnPullDownListener listener) {
    this.listView = listView;
    this.listener = listener;
  }

  public void initPulldown() {
    listView.setOnScrollListener(scrolllistener);
  }

  public void stopPulldown() {
    listView.setOnScrollListener(null);
  }

  public interface OnPullDownListener {
    void onPullDown();
  }
}