Android-RecyclerView分割线(水平/垂直/网格)

// 设置水平分割线
rv.setLayoutManager(new LinearLayoutManager(cxt));
rv.addItemDecoration(new GridItemDecoration(1, 0, cxt.getResources().getColor(R.color.gray_dim), true));

// 设置3列网格分割线
recyclerView.setLayoutManager(new GridLayoutManager(context, 3));
recyclerView.addItemDecoration(new GridItemDecoration(1, 1, mAct.getResources().getColor(R.color.gray_dim), true)); 

public class GridItemDecoration extends RecyclerView.ItemDecoration
{
	private int mHorizonLineWidth;
	private int mVerticalLineWidth;
	private Drawable mDividerDrawable;
	private boolean isDrawLastLine;

	/**
	 * 构造分割线
	 *
	 * @param horizonLineWidth  水平分割线宽
	 * @param verticalLineWidth 垂直分割线宽
	 * @param dividerColor      分割线颜色
	 * @param isDrawLastLine    是否绘制最后一行分割线
	 */
	public GridItemDecoration(int horizonLineWidth, int verticalLineWidth, int dividerColor, boolean isDrawLastLine)
	{
		this.mHorizonLineWidth = horizonLineWidth;
		this.mVerticalLineWidth = verticalLineWidth;
		this.isDrawLastLine = isDrawLastLine;
		this.mDividerDrawable = new ColorDrawable(dividerColor);
	}

	@Override
	public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state)
	{
		// drawHorizontal
		int childCount = parent.getChildCount();
		for (int i = 0; i < childCount; i++)
		{
			View child = parent.getChildAt(i);
			if (!isDrawLastLine && isLastRaw(parent, i, getSpanCount(parent), childCount))
				continue;
			RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
			final int left = child.getLeft() - params.leftMargin;
			final int right = child.getRight() + params.rightMargin;
			final int top = child.getBottom() + params.bottomMargin;
			final int bottom = top + mHorizonLineWidth;
			mDividerDrawable.setBounds(left, top, right, bottom);
			mDividerDrawable.draw(c);
		}

		// drawVertical
		int childCount1 = parent.getChildCount();
		for (int i = 0; i < childCount1; i++)
		{
			final View child = parent.getChildAt(i);
			if ((parent.getChildViewHolder(child).getAdapterPosition() + 1) % getSpanCount(parent) == 0)
				continue;
			final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
			final int top = child.getTop() - params.topMargin;
			final int bottom = child.getBottom() + params.bottomMargin + mHorizonLineWidth;
			final int left = child.getRight() + params.rightMargin;
			int right = left + mVerticalLineWidth;
			mDividerDrawable.setBounds(left, top, right, bottom);
			mDividerDrawable.draw(c);
		}
	}

	@Override
	public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state)
	{
		int spanCount = getSpanCount(parent);
		int childCount = parent.getAdapter().getItemCount();
		int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();
		if (itemPosition < 0)
			return;
		int column = itemPosition % spanCount;
		int bottom;
		int left = column * mVerticalLineWidth / spanCount;
		int right = mVerticalLineWidth - (column + 1) * mVerticalLineWidth / spanCount;
		if (isLastRaw(parent, itemPosition, spanCount, childCount))
			bottom = isDrawLastLine ? mHorizonLineWidth : 0;
		else
			bottom = mHorizonLineWidth;
		outRect.set(left, 0, right, bottom);
	}

	private int getSpanCount(RecyclerView parent)
	{
		int spanCount = -1;
		RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
		if (layoutManager instanceof GridLayoutManager)
			spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
		else if (layoutManager instanceof StaggeredGridLayoutManager)
			spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
		return spanCount;
	}

	private boolean isLastRaw(RecyclerView parent, int pos, int spanCount, int childCount)
	{
		RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
		if (layoutManager instanceof GridLayoutManager)
		{
			int remainCount = childCount % spanCount;
			if (remainCount == 0)
				return pos >= childCount - spanCount;
			else
				return pos >= childCount - childCount % spanCount;
		}
		else if (layoutManager instanceof StaggeredGridLayoutManager)
		{
			int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();
			if (orientation == StaggeredGridLayoutManager.VERTICAL)
			{
				// 水平滚动
				int remainCount = childCount % spanCount;
				if (remainCount == 0)
					return pos >= childCount - spanCount;
				else
					return pos >= childCount - childCount % spanCount;
			}
			else // 垂直滚动
				return (pos + 1) % spanCount == 0;
		}
		else if (layoutManager instanceof LinearLayoutManager)
		{
			return pos >= parent.getAdapter().getItemCount() - 1;
		}
		return false;
	}
}