android - 当列表按降序排序时，DiffUtil 正在改变我的位置

Question

我正在使用 diff util 来提高我的 recyclerview 的性能，而不是调用 notifyDataSetChanged()。 recyclerview 有一个带有一些芯片的标题，可以通过 aplhabetical 顺序重新排序列表，最高分数等
当我单击标题中的筹码时，列表会对其重新排序，从而影响我的位置。例如，如果我按最高分数排序并且分数 100% 是位置 1(在标题之后)，我单击芯片以反向重新排序。分数 100% 现在将位于列表的底部，而 0% 将位于顶部。但现在我必须一直滚动到顶部才能再次看到标题芯片。我希望列表重新排序，但我不希望我在屏幕上的位置改变。

这是我的适配器代码:

class DigitalTestsResultsAdapter(
private val interaction: Interaction? = null,
private val dateUtil: DateUtil,
private val theme: ThemeModel?,
private val username: String?
) : ListAdapter<ResultResponseModel, RecyclerView.ViewHolder>(ResultsDiffCallBack()) {

private val itemViewTypeHeader: Int = 0
private val itemViewTypeItem: Int = 1
private var filteredList = emptyList<ResultResponseModel>()
private val adapterScope = CoroutineScope(Dispatchers.Default)

class ResultsDiffCallBack : DiffUtil.ItemCallback<ResultResponseModel>() {
    override fun areItemsTheSame(
        oldItem: ResultResponseModel,
        newItem: ResultResponseModel
    ): Boolean {
        return oldItem.certificateUrl == newItem.certificateUrl
    }

    @SuppressLint("DiffUtilEquals")
    override fun areContentsTheSame(
        oldItem: ResultResponseModel,
        newItem: ResultResponseModel
    ): Boolean {
        return oldItem == newItem
    }
}

fun filterList(list: List<ResultResponseModel>, type: String) {
    adapterScope.launch {
        when (type) {

            "courseName" -> {
                filteredList = list.sortedBy { it.courseName }
            }

            "isCpd" -> {
                filteredList = list.sortedBy { it.courseName }.sortedByDescending { it.isCPD }
            }

            "organisationName" -> {
                filteredList = list.sortedBy { it.organisationName }
            }

            "roleName" -> {
                filteredList = list.sortedBy { it.roleName }
            }

            "score" -> {
                filteredList = list.sortedByDescending { it.score }
            }

            "submitTime" -> {
                filteredList = list.sortedByDescending { it.submitTime }
            }
        }
        withContext(Dispatchers.Main) {
            submitList(filteredList)
        }
    }
}


override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
    return when (viewType) {

        itemViewTypeHeader -> {
            DigitalTestsResultsHeaderViewHolder(
                RvDigitalTestResultsHeaderBinding.inflate(
                    LayoutInflater.from(parent.context),
                    parent,
                    false
                )
            )
        }

        itemViewTypeItem -> {
            DigitalTestsResultsViewHolder(
                RvDigitalTestsResultsBinding.inflate(
                    LayoutInflater.from(parent.context),
                    parent,
                    false
                ),
                interaction = interaction
            )
        }

        else -> throw ClassCastException("Unknown viewType $viewType")

    }
}

override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
    when (holder) {

        is DigitalTestsResultsHeaderViewHolder -> {
            holder.bind()
        }

        is DigitalTestsResultsViewHolder -> {
            holder.bind(currentList[position])
        }

    }
}

override fun getItemViewType(position: Int): Int {
    return if (position == 0) {
        itemViewTypeHeader
    } else {
        itemViewTypeItem
    }
}

override fun getItemCount(): Int {
    return if (!currentList.isNullOrEmpty()) {
        currentList.size
    } else 0
}

inner class DigitalTestsResultsHeaderViewHolder
constructor(
    private val binding: RvDigitalTestResultsHeaderBinding
) : RecyclerView.ViewHolder(binding.root) {

    fun bind() {
        with(binding) {
            with(theme) {

                userName.text = itemView.context.getString(R.string.hi_username, username)
                userName.setTextColourHex(this?.textModel?.primaryColor)
                chipCv.setCardBackgroundColourHex(this?.interfaceModel?.secondaryColor)

                testsChipGroup.setOnCheckedChangeListener { _, checkedId ->
                    when (checkedId) {

                        R.id.chipCertified -> {
                            chipCertified.isChecked = true
                            filterList(currentList, "isCpd")
                        }

                        R.id.chipCourse -> {
                            chipCourse.isChecked = true
                            filterList(currentList, "courseName")
                        }

                        R.id.chipHighestScore -> {
                            chipHighestScore.isChecked = true
                            filterList(currentList, "score")
                        }

                        R.id.chipRecent -> {
                            chipRecent.isChecked = true
                            filterList(currentList, "submitTime")
                        }

                        R.id.chipRole -> {
                            chipRole.isChecked = true
                            filterList(currentList, "roleName")
                        }

                        R.id.chipSchoolName -> {
                            chipSchoolName.isChecked = true
                            filterList(currentList, "organisationName")
                        }
                        else -> {

                        }
                    }
                }
            }
        }
    }
}

inner class DigitalTestsResultsViewHolder
constructor(
    private val binding: RvDigitalTestsResultsBinding,
    private val interaction: Interaction?
) : RecyclerView.ViewHolder(binding.root) {

    @SuppressLint("SetTextI18n")
    fun bind(item: ResultResponseModel?) {
        with(binding) {
            with(theme) {

                viewCertificateBtn.setOnClickListener {
                    interaction?.onItemSelected("certificateBtn", absoluteAdapterPosition, item)
                }

                retakeTestBtn.setOnClickListener {
                    interaction?.onItemSelected("retakeTestBtn", absoluteAdapterPosition, item)
                }

                resultsProgressBar.progress = item?.score?.toFloat() ?: 0f

                if (isValidHex(item?.roleColour)) {
                    resultsProgressBar.circleProgressColor = Color.parseColor(item?.roleColour)
                    resultsProgressBar.pointerColor = Color.parseColor(item?.roleColour)
                }

                score.text = item?.score.toString() + "%"
                title.text = item?.courseName
                date.text = dateUtil.formatStringDateToDDMMYYYY(item?.submitTime)
                role.text = item?.roleName
                schoolName.text = item?.organisationName

                title.setTextColourHex(this?.textModel?.primaryColor)
                retakeTestBtn.setTextColourHex(this?.textModel?.primaryColor)
                mainCv.setCardBackgroundColourHex(this?.interfaceModel?.secondaryColor)
                roleCv.setCardBackgroundColourHex(item?.roleColour)

                // Check if course is CPD and display CPD icon
                if (item?.isCPD == true) cpdLogo.visibility =
                    View.VISIBLE else cpdLogo.visibility = View.INVISIBLE
            }
        }
    }
}

interface Interaction {
    fun onItemSelected(
        tag: String,
        position: Int,
        result: ResultResponseModel?
    )
}
}

Answer 1

使用 registerAdapterDataObserver 注册适配器以观察以在数据更改时通知您adapter.registerAdapterDataObserver()当数据更改时，将 recyclerView 滚动到第一项位置
使用 recyclerview.scrollToPosition(position)也可以看看:
Recycler view scroll to specific position
和 Diffutil in recycleview, making it autoscroll if a new item is added