some suggest and some problem

[ChoicesWang]

Sorry.My English not good.
我认为应该分成 GridItemDecoration 和 LinearItemDecoration 。在每个item的周围绘制想要的divider。
这样实现起来比较简单。如果是GridLayoutManager，垂直的时候，则应该在最后一列右边 和 最后一行的下面不添加分割线。
下面是我写的一个例子，相信你能看懂

I think it should be divided into GridItemDecoration and LinearItemDecoration.Draw divider around each item instead of entire row / column.
If it's GridLayoutManager, you should not add the dividing line in the last column to the right and below the last line when vertical and vice versa.
I just like to think of it, it's easier for me to think of it, as the work that I do.
Here is an example of what I wrote, I believe you can understand

public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
    RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
    if (layoutManager instanceof GridLayoutManager) {
        outRect.left = getDividerSize();
        outRect.bottom = getDividerSize();
        GridLayoutManager gridLayoutManager = (GridLayoutManager) layoutManager;
        RecyclerView.Adapter adapter = parent.getAdapter();
        int itemCount = adapter.getItemCount();
        int position = parent.getChildAdapterPosition(view);
        int spanCount = gridLayoutManager.getSpanCount();
        GridLayoutManager.SpanSizeLookup spanSizeLookup = gridLayoutManager.getSpanSizeLookup();
        int spanIndex = spanSizeLookup.getSpanIndex(position, spanCount);
        int spanGroupIndex = spanSizeLookup.getSpanGroupIndex(position, spanCount);
        int lastSpanGroupIndex = spanSizeLookup.getSpanGroupIndex(itemCount - 1, spanCount);
        if (lastSpanGroupIndex == spanGroupIndex) outRect.bottom = 0;
        if (spanIndex == 0) outRect.left = 0;
        return;
    }
    Log.e(TAG, "RecyclerView must have GridLayoutManager");
}