RecyclerView添加Header和Footer

本文是来自于
RecyclerView添加Header的正确方式(http://blog.csdn.net/qibin0506/article/details/49716795)
的一个扩展。实现原理作者已经介绍的很清楚，就不再赘述。原文作者针对于Header的添加做了详细介绍，本人对其稍加修改，添加了Footer的部分。

可以方便解决类似上图对齐的困扰，话不多少，直接上代码

public abstract class BaseRecyclerAdapter<T> extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    public static final int TYPE_HEADER = 0;
    public static final int TYPE_NORMAL = 1;
    public static final int TYPE_FOOTER = 2;

    private ArrayList<T> mDatas = new ArrayList<>();

    private View mHeaderView,mFooterView;

    private OnItemClickListener mListener;

    public void setOnItemClickListener(OnItemClickListener li) {
        mListener = li;
    }

    public void setHeaderView(View headerView) {
        mHeaderView = headerView;
        notifyItemInserted(0);
    }

    public View getHeaderView() {
        return mHeaderView;
    }

    public View getFooterView() {
        return mFooterView;
    }

    public void setFooterView(View mFooterView) {
        this.mFooterView = mFooterView;
    }

    public void addDatas(ArrayList<T> datas) {
        mDatas.addAll(datas);
        notifyDataSetChanged();
    }

    @Override
    public int getItemViewType(int position) {
        if (mHeaderView == null && mFooterView == null) return TYPE_NORMAL;
        if (position == 0 && mHeaderView != null) return TYPE_HEADER;
        if (mFooterView != null){
            if (mHeaderView == null && position == mDatas.size()) return TYPE_FOOTER;
            if (mHeaderView != null && position == mDatas.size() + 1) return TYPE_FOOTER;
        }
        return TYPE_NORMAL;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, final int viewType) {
        if (mHeaderView != null && viewType == TYPE_HEADER) return new Holder(mHeaderView);
        if (mFooterView != null && viewType == TYPE_FOOTER) return new Holder(mFooterView);
        return onCreate(parent, viewType);
    }


    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, int position) {
        if (getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_FOOTER) return;

        final int pos = getRealPosition(viewHolder);
        final T data = mDatas.get(pos);
        onBind(viewHolder, pos, data);

        if (mListener != null) {
            viewHolder.itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    mListener.onItemClick(pos, data);
                }
            });
        }
    }

    @Override
    public void onAttachedToRecyclerView(RecyclerView recyclerView) {
        super.onAttachedToRecyclerView(recyclerView);

        RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
        if (manager instanceof GridLayoutManager) {
            final GridLayoutManager gridManager = ((GridLayoutManager) manager);
            gridManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                @Override
                public int getSpanSize(int position) {
                    return (getItemViewType(position) == TYPE_HEADER || getItemViewType(position) == TYPE_FOOTER)
                            ? gridManager.getSpanCount() : 1;
                }
            });
        }
    }

    @Override
    public void onViewAttachedToWindow(RecyclerView.ViewHolder holder) {
        super.onViewAttachedToWindow(holder);
        ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();
        if (lp != null
                && lp instanceof StaggeredGridLayoutManager.LayoutParams) {
            StaggeredGridLayoutManager.LayoutParams p = (StaggeredGridLayoutManager.LayoutParams) lp;
            p.setFullSpan(holder.getLayoutPosition() == 0);
        }
    }

    public int getRealPosition(RecyclerView.ViewHolder holder) {
        int position = holder.getLayoutPosition();
        return mHeaderView == null ? position : position - 1;
    }

    @Override
    public int getItemCount() {
        return mHeaderView == null ? (mFooterView == null ? mDatas.size() : mDatas.size() + 1) : (mFooterView == null ? mDatas.size() + 1 : mDatas.size() + 2);
    }

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

    public abstract void onBind(RecyclerView.ViewHolder viewHolder, int RealPosition, T data);

    public class Holder extends RecyclerView.ViewHolder {
        public Holder(View itemView) {
            super(itemView);
        }
    }

    public interface OnItemClickListener<T> {
        void onItemClick(int position, T data);
    }
}