给RecyclerView添加头部和尾部最简单的实现方式

最新推荐文章于 2019-11-14 16:17:20 发布

原创最新推荐文章于 2019-11-14 16:17:20 发布 · 2.9k 阅读

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通过扩展RecyclerView.Adapter，可以便捷地为RecyclerView添加Header和Footer。只需修改getItemViewType和 getItemCount，并针对Grid和瀑布流布局重写相应方法，调整每个item的span数。

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参考：Android 优雅的为RecyclerView添加HeaderView和FooterView
其实实现的最简单的方式就是扩展一下RecyclerView.Adapter
伪代码如下：

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
    {
        if (viewType == HEADERTYPE)
        {

            ViewHolder holder = ViewHolder.createViewHolder(parent.getContext(), getHeaderView());
            return holder;

        } else if (viewType== FOOTERTYPE)
        {
            ViewHolder holder = ViewHolder.createViewHolder(parent.getContext(), getFooterView());
            return holder;
        }
        return mInnerAdapter.onCreateViewHolder(parent, viewType);
    }

当然还有getItemViewType方法：

    @Override
    public int getItemViewType(int position)
    {
        if (position==。。。)
        {
            return HEADERTYPE;
        } else if (position==。。。)
        {
            return FOOTERTYPE;
        }
        return mInnerAdapter.getItemViewType(position - getHeadersCount());
    }

最后ItemCount要加上头和尾的数量

@Override
    public int getItemCount()
    {
        return getHeadersCount() + getFootersCount() + getRealItemCount();
    }

实现上面的代码运行之后你会发现线性的没有问题了，但是Grid的和瀑布流的还是有问题，只需要再重写两个方法就可以了
针对Grid的

Override
public void onAttachedToRecyclerView(RecyclerView recyclerView)
{
    innerAdapter.onAttachedToRecyclerView(recyclerView);

    RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
    if (layoutManager instanceof GridLayoutManager)
    {
        final GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
        final GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();

        gridLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup()
        {
            @Override
            public int getSpanSize(int position)
            {
               int viewType = getItemViewType(position);
              if (mHeaderViews.get(viewType) != null)
              {
                  return layoutManager.getSpanCount();
              } else if (mFootViews.get(viewType) != null)
              {
                  return layoutManager.getSpanCount();
              }
              if (oldLookup != null)
                  return oldLookup.getSpanSize(position);
              return 1;
            }
        });
        gridLayoutManager.setSpanCount(gridLayoutManager.getSpanCount());
    }
}

针对瀑布流的

@Override
public void onViewAttachedToWindow(RecyclerView.ViewHolder holder)
{
    mInnerAdapter.onViewAttachedToWindow(holder);
    int position = holder.getLayoutPosition();
    if (isHeaderViewPos(position) || isFooterViewPos(position))
    {
        ViewGroup.LayoutParams lp = holder.itemView.getLayoutParams();

        if (lp != null
                && lp instanceof StaggeredGridLayoutManager.LayoutParams)
        {

            StaggeredGridLayoutManager.LayoutParams p = 
                    (StaggeredGridLayoutManager.LayoutParams) lp;

            p.setFullSpan(true);
        }
    }
}

我都能看懂，基本也都能看懂，我这里就不解释了，改变一下单个item的占用的span数。