现在出现这个错误：Type mismatch: inferred type is View? but View was expected

这个错误是因为findContainingViewHolder()方法返回的是RecyclerView.ViewHolder?类型，可能为空，需要进行判空处理。修改代码如下： ``` override fun onLayoutChildren(recycler: RecyclerView.Recycler?, state: RecyclerView.State?) { super.onLayoutChildren(recycler, state) var totalHeight = 0 for (i in 0 until childCount) { val child = mRvChat.findContainingViewHolder(getChildAt(i))?.itemView if (child != null) { totalHeight += child.height } } if (totalHeight > height) { mRvChat.postDelayed({ mRvChat.smoothScrollToPosition(itemCount - 1) }, 1000) } } ``` 这样就可以避免Type mismatch: inferred type is View? but View was expected的问题了。