RecycleView 滑动到底部，加载更多

　　android.support.v7 包提供了一个新的组件：RecycleView，用以提供一个灵活的列表试图、显示大型数据集，它支持局部刷新、显示动画等功能，可以用来取代ListView与GridView.

　　然而在使用的过程中却遇到一些问题，基本现在手机页面都会有滑动到底部加载更多的功能，而RecycleView 并没有提供像ListView的addFooter等方法，所以实现起来还是有点麻烦。经过一段时间的摸索，终于找到实现RecycleView加载更多的方法。

　　本文主要通过RecycleView 的 ItemViewType 来实现RecycleView滑动到底部加载更多功能，支持 列表、网格、瀑布流等布局。

　　根据ItemViewType创建两种布局，一个用于显示正常内容的布局，一个用于加载布局，然后监听RecycleView的滚动事件，当滑动到底部时添加加载布局，对于列表布局来说很简单，不再熬述，然而对于网格布局与瀑布流布局来说，要解决"加载布局只占用一列"的问题,

　　1.对于网格布局，GridLayoutManager 提供了一个 setSpanSizeLookup() 的方法，用来设置每个条目可以占用的列数，默认为1.

　　2.对于瀑布流，StaggeredGridLayoutManager 提供了一个 StaggeredGridLayoutManager.LayoutParams 内部静态类，此类中有一个setFullSpan() 方法，用来设置条目跨越全列。

　　

　　3.基类的实现方式如下：子类只需要重写以下方法：

　　　　onCreateNormalViewHolder(ViewGroup parent);

　　　　onBindNormalViewHolder(RecyclerView.ViewHolder holder, int position);

 /**
  * Created by sunwei on 2015/12/4.
  * Email: lx_sunwei@163.com.
  * Description: recycleView 滑动到底部加载更多
  */
 public abstract class BaseLoadingAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

     private static final String TAG = "BaseLoadingAdapter";

     //是否正在加载
     public boolean mIsLoading = false;
     //正常条目
     private static final int TYPE_NORMAL_ITEM = 0;
     //加载条目
     private static final int TYPE_LOADING_ITEM = 1;
     //加载viewHolder
     private LoadingViewHolder mLoadingViewHolder;
     //瀑布流
     private StaggeredGridLayoutManager mStaggeredGridLayoutManager;
     //数据集
     private CircularArray<T> mTs;
     //首次进入
     private boolean mFirstEnter = true;
     private RecyclerView mRecyclerView;

     public BaseLoadingAdapter(RecyclerView recyclerView, CircularArray<T> ts) {

         mTs = ts;

         mRecyclerView = recyclerView;

         setSpanCount(recyclerView);

         //notifyLoading();
     }

     private OnLoadingListener mOnLoadingListener;

     /**
      * 加载更多接口
      */
     public interface OnLoadingListener {
         void loading();
     }

     /**
      * 设置监听接口
      *
      * @param onLoadingListener onLoadingListener
      */
     public void setOnLoadingListener(OnLoadingListener onLoadingListener) {
         setScrollListener(mRecyclerView);
         mOnLoadingListener = onLoadingListener;
     }

     /**
      * 加载完成
      */
     public void setLoadingComplete() {
         if (mTs.size() > 0 && mTs.getLast() == null) {
             mIsLoading = false;
             mTs.removeFromEnd(1);
             notifyItemRemoved(mTs.size() - 1);
         }
     }

     /**
      * 没有更多数据
      */
     public void setLoadingNoMore() {
         mIsLoading = false;
         if (mLoadingViewHolder != null) {
             mLoadingViewHolder.progressBar.setVisibility(View.GONE);
             mLoadingViewHolder.tvLoading.setText("已加载完！");
         }
     }

     /**
      * 加载失败
      */
     public void setLoadingError() {
         if (mLoadingViewHolder != null) {
             mIsLoading = false;
             mLoadingViewHolder.progressBar.setVisibility(View.GONE);
             mLoadingViewHolder.tvLoading.setText("加载失败，点击重新加载！");

             mLoadingViewHolder.tvLoading.setOnClickListener(new View.OnClickListener() {
                 @Override
                 public void onClick(View v) {
                     if (mOnLoadingListener != null) {
                         mIsLoading = true;
                         mLoadingViewHolder.progressBar.setVisibility(View.VISIBLE);
                         mLoadingViewHolder.tvLoading.setText("正在加载...");

                         mOnLoadingListener.loading();
                     }
                 }
             });
         }
     }

     /**
      * @return Whether it is possible for the child view of this layout to
      * scroll up. Override this if the child view is a custom view.
      */
     private boolean canScrollDown(RecyclerView recyclerView) {
         return ViewCompat.canScrollVertically(recyclerView, 1);
     }

     /**
      * 设置加载item占据一行
      *
      * @param recyclerView recycleView
      */
     private void setSpanCount(RecyclerView recyclerView) {
         RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();

         if (layoutManager == null) {
             Log.e(TAG, "LayoutManager 为空,请先设置 recycleView.setLayoutManager(...)");
         }

         //网格布局
         if (layoutManager instanceof GridLayoutManager) {
             final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
             gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                 @Override
                 public int getSpanSize(int position) {
                     int type = getItemViewType(position);
                     if (type == TYPE_NORMAL_ITEM) {
                         return 1;
                     } else {
                         return gridLayoutManager.getSpanCount();
                     }
                 }
             });
         }

         //瀑布流布局
         if (layoutManager instanceof StaggeredGridLayoutManager) {
             mStaggeredGridLayoutManager = (StaggeredGridLayoutManager) layoutManager;
         }
     }

     /**
      * 显示加载
      */
     private void notifyLoading() {
         if (mTs.size() != 0 && mTs.getLast() != null) {
             mTs.addLast(null);
             notifyItemInserted(mTs.size() - 1);
         }
     }

     /**
      * 监听滚动事件
      *
      * @param recyclerView recycleView
      */
     private void setScrollListener(RecyclerView recyclerView) {
         if(recyclerView == null) {
             Log.e(TAG, "recycleView 为空");
             return;
         }

         recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
             @Override
             public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                 super.onScrollStateChanged(recyclerView, newState);
             }

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

                 if (!canScrollDown(recyclerView)) {

                     //首次进入不加载
                     if (!mIsLoading && !mFirstEnter) {

                         notifyLoading();

                         mIsLoading = true;

                         if (mLoadingViewHolder != null) {
                             mLoadingViewHolder.progressBar.setVisibility(View.VISIBLE);
                             mLoadingViewHolder.tvLoading.setText("正在加载...");
                         }

                         if (mOnLoadingListener != null) {
                             mOnLoadingListener.loading();
                         }
                     }
                 }

                 if (mFirstEnter) {
                     mFirstEnter = false;
                 }
             }
         });
     }

     /**
      * 创建viewHolder
      *
      * @param parent viewGroup
      * @return viewHolder
      */
     public abstract RecyclerView.ViewHolder onCreateNormalViewHolder(ViewGroup parent);

     /**
      * 绑定viewHolder
      *
      * @param holder   viewHolder
      * @param position position
      */
     public abstract void onBindNormalViewHolder(RecyclerView.ViewHolder holder, int position);

     /**
      * 加载布局
      */
     private class LoadingViewHolder extends RecyclerView.ViewHolder {
         public ProgressBar progressBar;
         public TextView tvLoading;
         public LinearLayout llyLoading;

         public LoadingViewHolder(View view) {
             super(view);

             progressBar = (ProgressBar) view.findViewById(R.id.progress_loading);
             tvLoading = (TextView) view.findViewById(R.id.tv_loading);
             llyLoading = (LinearLayout) view.findViewById(R.id.lly_loading);
         }
     }

     @Override
     public int getItemViewType(int position) {
         T t = mTs.get(position);
         if (t == null) {
             return TYPE_LOADING_ITEM;
         } else {
             return TYPE_NORMAL_ITEM;
         }
     }

     @Override
     public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         if (viewType == TYPE_NORMAL_ITEM) {
             return onCreateNormalViewHolder(parent);
         } else {
             View view = LayoutInflater.from(parent.getContext()).inflate(
                     R.layout.loading_layout, parent, false);
             mLoadingViewHolder = new LoadingViewHolder(view);
             return mLoadingViewHolder;
         }
     }

     @Override
     public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
         int type = getItemViewType(position);
         if (type == TYPE_NORMAL_ITEM) {
             onBindNormalViewHolder(holder, position);
         } else {

             if (mStaggeredGridLayoutManager != null) {
                 StaggeredGridLayoutManager.LayoutParams layoutParams =
                         new StaggeredGridLayoutManager.LayoutParams(
                                 ViewGroup.LayoutParams.MATCH_PARENT,
                                 ViewGroup.LayoutParams.WRAP_CONTENT);
                 layoutParams.setFullSpan(true);

                 mLoadingViewHolder.llyLoading.setLayoutParams(layoutParams);
             }
         }
     }

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

Base Loading Adapter

4.一个简单的列子

 /**
  * Created by sunwei on 2015/12/4.
  * Email: lx_sunwei@163.com.
  * Description: 滑动到底部加载更多
  */
 public class DesignLoaderMoreAdapter extends BaseLoadingAdapter<DesignItem> {

     private CircularArray<DesignItem> mDesignItems;

     public DesignLoaderMoreAdapter(RecyclerView recyclerView, CircularArray<DesignItem> datas) {
         super(recyclerView, datas);

         mDesignItems = datas;
     }

     //正常条目
     public  class DesignViewHolder extends RecyclerView.ViewHolder {
         public TextView  textView;
         public CardView cardView;
         public DesignViewHolder(View view) {
             super(view);
             textView = (TextView) view.findViewById(R.id.tv_design);
             cardView = (CardView) view.findViewById(R.id.cardView_designer);

         }
     }

     @Override
     public RecyclerView.ViewHolder onCreateNormalViewHolder(ViewGroup parent) {
         View view = LayoutInflater.from(parent.getContext()).inflate(
                 R.layout.list_item_design, parent, false);
         return new DesignViewHolder(view);
     }

     @Override
     public void onBindNormalViewHolder(RecyclerView.ViewHolder holder, int position) {
         DesignViewHolder viewHolder = (DesignViewHolder)holder;
         DesignItem designItem = mDesignItems.get(position);
         if (position == 10) {
             //设置瀑布流的条目大小
             LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(260, 360);
             lp.setMargins(10, 40, 10, 80);
             viewHolder.cardView.setLayoutParams(lp);
         }

         viewHolder.textView.setText(designItem.name);
     }
 }

Sample

　　    

项目地址：https://github.com/lxsunwei/MaterialDesign