如何使用 StaggeredGridLayoutManager 在 RecyclerView 中确定 viewholder 是左还是右

Question

我已经阅读了很多类似的文章，但仍然没有找到如何在 RecyclerView 和 StaggeredGridLayoutManager 中知道 view holder 是左还是右的答案。

情况：我有 RecyclerView、StaggeredGrid 并且想要填充

8 dp [left view] 8 dp [right view] 8 dp

因为我不能在 XML 中做到这一点，所以我必须添加一些边距 -

对于左视图：左边距 8dp，右边距 4dp

对于右视图：左边距 4dp，右边距 8dp

通常视图是这样放置的：

[0][1]
[2][3]
[4][5]

最简单的解决方案是尝试按位置确定它：

override fun onBindViewHolder(ViewHolder holder, int position) {
    ...
        val params = holder.cardView.layoutParams as FrameLayout.LayoutParams

        if (position % 2 == 0) {
            params.leftMargin = pxFromDp(context, 8f).toInt()
            params.rightMargin = pxFromDp(context, 4f).toInt()
        }
        if (position % 2 == 1) {
            params.rightMargin = pxFromDp(context, 8f).toInt()
            params.leftMargin = pxFromDp(context, 4f).toInt()
        }
        params.bottomMargin = pxFromDp(context, 2f).toInt()
        params.topMargin = pxFromDp(context, 6f).toInt()

        holder.cardView.layoutParams = params
    ...
}

这行得通，但是如果视图 2 的高度小于视图 1，它们就会被放置

[0][1]
[3][2]
[5][4]

所以它不起作用。

我怎么知道是左取景器还是右取景器？

Answer 1

唯一真正有帮助的选项是使用自定义 RecyclerView.ItemDecoration()

class StaggeredGridDecoration(val margin: Int) : RecyclerView.ItemDecoration() {
    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State?) {
        super.getItemOffsets(outRect, view, parent, state)
        val position = parent.getChildAdapterPosition(view)
        val spanIndex = (view.layoutParams as StaggeredGridLayoutManager.LayoutParams).spanIndex
        val type = parent.adapter.getItemViewType(position)
        val halfOfMargin = margin / 2
        when (type) {
            1 -> {//use here 0 if you didnt create custom types
                var top = 0
                val bottom = pxFromDp(parent.context, margin.toFloat()).toInt()
                //for first 2 elements I need additional margin top
                if (position < 3) {
                    top = pxFromDp(parent.context, margin.toFloat()).toInt()
                }
                if (spanIndex == 0) {
                    //settings for left column
                    val left = pxFromDp(parent.context, margin.toFloat()).toInt()
                    val right = pxFromDp(parent.context, halfOfMargin.toFloat()).toInt()
                    setMargins(view, left, right, top, bottom)
                } else {
                    //settings for right column
                    val left = pxFromDp(parent.context, halfOfMargin.toFloat()).toInt()
                    val right = pxFromDp(parent.context, margin.toFloat()).toInt()
                    setMargins(view, left, right, top, bottom)
                }
            }
        }
    }

    private fun setMargins(view: View, left: Int, right: Int, top: Int, bottom: Int) {
        val cardView: CardView = view.findViewById(R.id.cardView)
        val params = cardView.layoutParams as FrameLayout.LayoutParams

        params.rightMargin = right
        params.leftMargin = left
        params.bottomMargin = bottom
        params.topMargin = top

        cardView.layoutParams = params
    }

}

刚刚添加了它

recyclerView.addItemDecoration(new StaggeredGridDecoration(8));

如何使用 StaggeredGridLayoutManager 在 RecyclerView 中确定 viewholder 是左还是右

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