如何在Android中利用Recyclerview实现一个上拉加载功能

 @Override
 public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    super.onScrolled(recyclerView, dx, dy);
   }

package com.appnews.utils;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
/**
 * Created by Administrator on 2017/5/17.
 */
public class LoadMoreForRecyclerView {
 //最后一个显示的item的position
 private int lastVisibleItemPosition;
 //触摸记录之前的触摸位置
 private float oldY;
 //滑动状态
 private int state;
 //滑动时Y轴偏移（大于0表示向上滑动）
 private int offsetY = 0;
 //touch事件中移动的距离（当前触摸的位置-oldY）
 private float moveY;
 /**
  * 构造方法
  * @param recyclerView
  * @param loadMoreListener
  */
 public LoadMoreForRecyclerView(RecyclerView recyclerView, LoadMoreListener loadMoreListener) {
  width(recyclerView, loadMoreListener);
 }
 /**
  *
  * @param recyclerView recyclerview
  * @param loadMoreListener 回调监听
  */
 public void width(final RecyclerView recyclerView, LoadMoreListener loadMoreListener) {
  mLoadMoreListener = loadMoreListener;
  //线性布局管理
  final LinearLayoutManager linearLayoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
  //recyclerview设置滑动监听
  recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
   @Override
   public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
    super.onScrollStateChanged(recyclerView, newState);
    //滑动状态
    state = newState;
    //获得最后一个显示的item位置
    lastVisibleItemPosition = linearLayoutManager.findLastVisibleItemPosition();
   }
   @Override
   public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
    super.onScrolled(recyclerView, dx, dy);
    //记录Y轴偏移量
    offsetY = dy;
   }
  });
  //设置touch监听
  recyclerView.setOnTouchListener(new View.OnTouchListener() {
   @Override
   public boolean onTouch(View view, MotionEvent motionEvent) {
    switch (motionEvent.getAction()) {
     case MotionEvent.ACTION_MOVE:
      //计算出移动的距离（小于0表示向上拖动）
      moveY = motionEvent.getY() - oldY;
      //记录当前触摸的位置
      oldY = motionEvent.getY();
      break;
     case MotionEvent.ACTION_UP:
      //如果是拖动或者飞快滑动并且显示的是适配器中最后一条数据
      if ((state == 1 || state == 2) && lastVisibleItemPosition == recyclerView.getAdapter().getItemCount() - 1) {
       if (offsetY > 0) {//如果偏移量大于0
        if (mLoadMoreListener != null) {
         //回调加载更多监听
         mLoadMoreListener.loadListener();
        }
       } else if (offsetY == 0) {//如果偏移量一直等于0
        if ((moveY) < 0) {//手指移动的距离小于0（向上拖动recyclerView）
         if (mLoadMoreListener != null) {
          //回调加载更多
          mLoadMoreListener.loadListener();
         }
        }
       }
      }
      break;
    }
    //返回值要为false，不会拦截滑动事件
    return false;
   }
  });
 }
 private LoadMoreListener mLoadMoreListener;
 /**
  * 回调接口
  */
 public interface LoadMoreListener {
  void loadListener();
 }
}

//上拉加载更多滑动监听
  new LoadMoreForRecyclerView(rc, new LoadMoreForRecyclerView.LoadMoreListener() {
   @Override
   public void loadListener() {
    showToast("开始加载");
    getData(2);
   }
  });