DiffUtil 未更新 RecyclerView

Question

我为 recyclerView 制作了一个适配器，并使用 DiffUtil 以更有趣的方式显示列表的更新。我使用谷歌代码实验室作为参考。但是列表没有从以下代码更新。请帮忙

class LaptopAdapter : ListAdapter<Laptop, LaptopAdapter.ViewHolder>(Diff()) {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder.from(parent)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val item = getItem(position)
        holder.bind(item)
    }

    class ViewHolder private constructor(itemView: View) : RecyclerView.ViewHolder(itemView) {
        var ramText: TextView = itemView.findViewById(R.id.ramText)
        var diskText: TextView = itemView.findViewById(R.id.diskText)
        var screenText: TextView = itemView.findViewById(R.id.screenText)
        var osText: TextView = itemView.findViewById(R.id.osText)

        fun bind(item: Laptop) {
            ramText.text = item.ram.toString()
            diskText.text = item.disk
            screenText.text = item.screen.toString()
            osText.text = item.os
        }

        companion object {
            fun from(parent: ViewGroup) =
                    ViewHolder(LayoutInflater.from(parent.context).inflate(R.layout.item, parent, false))
        }
    }
}

class Diff : DiffUtil.ItemCallback<Laptop>() {
    override fun areItemsTheSame(oldItem: Laptop, newItem: Laptop): Boolean {
        return oldItem.id == newItem.id
    }

    override fun areContentsTheSame(oldItem: Laptop, newItem: Laptop): Boolean {
        return oldItem == newItem
    }
}

我的 MainActivity 文件是

setContentView(R.layout.activity_main)

        val list: ArrayList<Laptop> = ArrayList()
        list.add(Laptop(11, 4, "SSD", 14, "Windows"))
        list.add(Laptop(12, 4, "HDD", 14, "Ubuntu"))
        list.add(Laptop(17, 16, "SSD", 14, "Windows"))
        list.add(Laptop(13, 8, "SSD", 14, "Windows"))

        val rv: RecyclerView = findViewById(R.id.rv)
        rv.layoutManager = LinearLayoutManager(this)
        val adapter = LaptopAdapter()
        rv.adapter = adapter
        adapter.submitList(list)

        val btn: Button = findViewById(R.id.btn)
        btn.setOnClickListener {
            list.add(Laptop(15, 12, "HDD", 12, "DOS"))
            list.sortBy {
                it.ram
            }
            adapter.submitList(list)
        }

我尝试了以前的 stackOverflow 答案，但没有一个有效。请帮忙

Answer 1

如果您检查ListAdapter如何submitList工作的源代码，您会发现这部分代码：

if (newList == mList) {
   // nothing to do (Note - still had to inc generation, since may have ongoing work)
   return;
}

因此，除非您使用相同的引用传递列表，否则您将永远不会更新您的列表。要使其工作，您可以简单地调用：

adapter.submitList(list.toList())