android - Android RecyclerView SubmitList无法在LiveData观察器中更新数据

Question

我正在尝试使用LiveData Observer中的SubmitList更新嵌套的RecyclerView列表。
该列表已提交，但是仅当您触摸屏幕时，UI才会更新。
当我在主RecyclerView中添加嵌套的RecyclerViews时出现了问题。
所以我认为这与它有关。

我希望在调用commitList之后更新它。
我究竟做错了什么？

外部ListAdapter:

class ReservationAdapter(
        private val changeState: (visit: Visit, newState: Visit.State) -> MutableLiveData<Visit?>
) : ListAdapter<Reservation, ReservationViewHolder>(ReservationDiffCallback()) {
    private val recycledViewPool = RecyclerView.RecycledViewPool()

    /// Filters \\\
    // Building
    var filterBuildingId = ""
        set(value) {
            field = value
            filteredVisits = visits.filter(Visit.filter(value, filterSearchString))
        }

    // Search string
    var filterSearchString = ""
    set(value) {
        field = value
        filteredVisits = visits.filter(Visit.filter(filterBuildingId, value))
    }

    /// Filtering chain \\\
    // Visits come in and get filtered
    var visits = arrayListOf<Visit>()
        set(value) {
            field = value
            filteredVisits = value.filter(Visit.filter(filterBuildingId, filterSearchString))
        }

    // Filtered visits come in, a reservation map is made
    var filteredVisits = listOf<Visit>()
        set(value) {
            field = value
            reservationVisits = Reservation.extractMapFromVisits(value)
        }

    // Reservation map comes in, and submits a list of reservations
    private var reservationVisits = hashMapOf<Reservation, ArrayList<Visit>>()
        set(value) {
            field = value
            _reservationVisits.value = value
            submitList(value.keys.toMutableList())
            notifyDataSetChanged()
        }
    private val _reservationVisits = MutableLiveData<HashMap<Reservation, ArrayList<Visit>>>()


    /**
     * Inflate items
     */
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ReservationViewHolder {
        return ReservationViewHolder(
                LayoutInflater.from(parent.context).inflate(
                        R.layout.list_reservation,
                        parent,
                        false
                ),
                recycledViewPool,
                changeState,
                _reservationVisits
        )
    }

    /**
     * Bind items
     */
    override fun onBindViewHolder(holder: ReservationViewHolder, position: Int) {
        val reservation = getItem(position)
        holder.bind(reservation, reservationVisits[reservation])
    }
}

外部ViewHolder:

class ReservationViewHolder(
        private val view: View,
        private val recycledViewPool: RecyclerView.RecycledViewPool,
        changeState: (visit: Visit, newState: Visit.State) -> MutableLiveData<Visit?>,
        reservationVisits: MutableLiveData<HashMap<Reservation, ArrayList<Visit>>>
) : RecyclerView.ViewHolder(view) {
    private val adapter = VisitAdapter(changeState)
    private var _reservation: Reservation? = null

    init {
/*
THIS IS WHERE I SETS THE VALUE, BUT DOESN'T UPDATE THE UI.
*/
        reservationVisits.observe(view.context as LifecycleOwner) {
            if (_reservation != null) {
                (view.context as MainActivity).runOnUiThread {
                    adapter.submitList(null)
                    adapter.notifyDataSetChanged()
                    adapter.submitList(it[_reservation!!]?.toMutableList())
                    adapter.notifyDataSetChanged()
                    view.refreshDrawableState()
                }
            }
        }
    }

    fun bind(reservation: Reservation, visits: ArrayList<Visit>?): View = with(view) {
        println("3: ${visits?.size}")
        _reservation = reservation
        // Initialize values
        txtSubject.text = reservation.subject
        txtTime.text = "TIME"
        // Recycler view for visits
        rcvVisits.apply {
            (itemAnimator as SimpleItemAnimator).supportsChangeAnimations = false
            layoutManager = LinearLayoutManager(context)
            adapter = this@ReservationViewHolder.adapter
            setRecycledViewPool(this@ReservationViewHolder.recycledViewPool)
        }

        // Add visits to adapter
        adapter.submitList(visits)

        // Return view
        view
    }
}

内部ListAdapter:

class VisitAdapter(
        private val changeState: (visit: Visit, newState: Visit.State) -> MutableLiveData<Visit?>
) : ListAdapter<Visit, VisitViewHolder>(VisitDiffCallback()) {
    // Sorter
    private val _visitSorter = compareBy<Visit>({ it.state }, { it.expectedArrival }, { it.visitor?.name })

    // ListAdapter create
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VisitViewHolder {
        return VisitViewHolder(
                LayoutInflater.from(parent.context).inflate(
                        R.layout.list_visitor,
                        parent,
                        false
                ),
                changeState
        )
    }

    // ListAdapter bind
    override fun onBindViewHolder(holder: VisitViewHolder, position: Int) {
        holder.bind(getItem(position))
    }

    // ListAdapter submit
    override fun submitList(list: List<Visit>?) {
        super.submitList(list?.sortedWith(_visitSorter) ?: listOf())
    }
}

Answer 1

我检查了您的代码，这些是我发现的:

您在 View 持有者类中创建了适配器的实例和观察者。

View 持有者将实例化多次，因此您不应在其中实例化适配器。检查这个link

如果要将数据传递给 View 持有者，则应在构造函数中进行操作，切勿在 View 持有者类中观察数据的变化。

因此您可以观察 Activity 中的数据并将数据传递给适配器。

无需在观察者中调用runOnUiThread。它已经在主线程(UI线程)上。

The events are dispatched on the main thread. If LiveData already has data set, it will be delivered to the observer. LiveData