选择一项时，使用 PagedListAdapter 的 RecyclerView 多选隐藏所有项目

问题描述

我正在尝试在我的应用中使用 recyclerView-Selection 实现 PagedListAdapter。 问题是当我点击并按住一个项目并进入选择模式时，所有项目都会消失。请参阅此 video 以获得更好的理解。

这是我的代码

// RecyclerView
implementation 'androidx.recyclerview:recyclerview:1.1.0'
implementation 'androidx.recyclerview:recyclerview-selection:1.1.0'

// Paging
implementation 'androidx.paging:paging-runtime-ktx:2.1.2'

首页片段

class HomeFragment : Fragment(),AlarmAdapter.OnItemClickListener,AlarmAdapter.OnStateChangeListener {

    companion object {
        fun newInstance() = HomeFragment()
    }

    private var tracker: SelectionTracker<Long>? = null
    private var _binding: HomeFragmentBinding? = null
    private val binding get() = _binding!!

    private lateinit var homeViewModel: HomeViewModel

    override fun onCreateView(
        inflater: LayoutInflater,container: ViewGroup?,savedInstanceState: Bundle?
    ): View {
        _binding = HomeFragmentBinding.inflate(inflater,container,false)

        val application = requireActivity().application
        val dataSource = LocalDatabase.getInstance(application).alarmDao
        val homeViewModelFactory = HomeViewModelFactory(dataSource,application)
        homeViewModel = ViewModelProvider(
            this,homeViewModelFactory
        ).get(HomeViewModel::class.java)

        return binding.root
    }

    override fun onDestroyView() {
        super.onDestroyView()
        _binding = null
    }

    override fun onViewCreated(view: View,savedInstanceState: Bundle?) {
        super.onViewCreated(view,savedInstanceState)

        val adapter = AlarmAdapter()
        adapter.setOnItemClickListener(this)
        adapter.setOnStateChangeListener(this)
        binding.root.setHasFixedSize(true)
        binding.root.adapter = adapter

        tracker = SelectionTracker.Builder(
            "selection-1",binding.root,ItemIdKeyProvider(binding.root),ItemLookup(binding.root),StorageStrategy.createLongStorage()
        ).withSelectionPredicate(SelectionPredicates.createSelectAnything())
            .build()

        if (savedInstanceState != null)
            tracker?.onRestoreInstanceState(savedInstanceState)

        adapter.setTracker(tracker)

        tracker?.addObserver(object : SelectionTracker.SelectionObserver<Long>() {
            override fun onSelectionChanged() {
                val nItems: Int? = tracker?.selection?.size()
                Timber.d("$nItems items selected")
            }
        })

        homeViewModel.getAlarms.observe(viewLifecycleOwner,adapter::submitList)
    }

    override fun onItemClicked(view: View,position: Int,alarmModel: AlarmModel) {
        Timber.d("onItemClicked()")
        findNavController().navigate(HomeFragmentDirections.actionHomeToAlarm(alarmModel))
    }

    override fun onStateChanged(view: View,alarmModel: AlarmModel) {
        homeViewModel.update(alarmModel)
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        tracker?.onSaveInstanceState(outState)
    }

    inner class ItemIdKeyProvider(private val recyclerView: RecyclerView) :
        ItemKeyProvider<Long>(SCOPE_MAPPED) {

        override fun getKey(position: Int): Long {
            return recyclerView.adapter?.getItemId(position)
                ?: throw IllegalStateException("RecyclerView adapter is not set!")
        }

        override fun getPosition(key: Long): Int {
            val viewHolder = recyclerView.findViewHolderForItemId(key)
            return viewHolder?.layoutPosition ?: RecyclerView.NO_POSITION
        }
    }

    inner class ItemLookup(private val rv: RecyclerView) : ItemDetailsLookup<Long>() {
        override fun getItemDetails(event: MotionEvent)
                : ItemDetails<Long>? {

            val view = rv.findChildViewUnder(event.x,event.y)
            if (view != null) {
                return (rv.getChildViewHolder(view) as AlarmAdapter.ViewHolder)
                    .getItemDetails()
            }
            return null
        }
    }
}

报警适配器

class AlarmAdapter : PagedListAdapter<AlarmModel,AlarmAdapter.ViewHolder>(diffCallback) {

    companion object {
        private val diffCallback = object : DiffUtil.ItemCallback<AlarmModel>() {
            override fun areItemsTheSame(
                oldItem: AlarmModel,newItem: AlarmModel
            ): Boolean =
                oldItem.id == newItem.id

            override fun areContentsTheSame(
                oldItem: AlarmModel,newItem: AlarmModel
            ): Boolean =
                oldItem.id == newItem.id
        }
    }

    init {
        setHasStableIds(true)
    }

    private lateinit var mOnItemClickLister: OnItemClickListener

    interface OnItemClickListener {
        fun onItemClicked(view: View,alarmModel: AlarmModel)
    }

    fun setOnItemClickListener(listener: OnItemClickListener) {
        mOnItemClickLister = listener
    }

    private lateinit var mOnStateChangeListener: OnStateChangeListener

    interface OnStateChangeListener {
        fun onStateChanged(view: View,alarmModel: AlarmModel)
    }

    fun setOnStateChangeListener(listener: OnStateChangeListener) {
        mOnStateChangeListener = listener
    }

    override fun onCreateViewHolder(parent: ViewGroup,viewType: Int): ViewHolder {
        return ViewHolder(
            AlarmRowLayoutBinding.inflate(
                LayoutInflater.from(parent.context),parent,false
            ).root
        )
    }

    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        fun getItemDetails(): ItemDetailsLookup.ItemDetails<Long> =
            object : ItemDetailsLookup.ItemDetails<Long>() {
                override fun getPosition(): Int = adapterPosition
                override fun getSelectionKey(): Long? = itemId
            }
    }

    override fun onBindViewHolder(holder: ViewHolder,position: Int) {
        val alarmModel = getItem(position)

        alarmModel?.let {
            with(AlarmRowLayoutBinding.bind(holder.itemView)) {
                val calendar = Calendar.getInstance()
                calendar.timeInMillis = alarmModel.time

                txtTime.text = "%d:%2d".format(
                    calendar.get(Calendar.HOUR),calendar.get(Calendar.MINUTE)
                )
                txtAmpm.text = if (calendar.get(Calendar.AM_PM) == 0) "AM" else "PM"
                txtTitle.text = alarmModel.label

                swEnable.isChecked = alarmModel.status
                swEnable.setOnClickListener {
                    alarmModel.status = swEnable.isChecked
                    mOnStateChangeListener.onStateChanged(it,position,alarmModel)
                }
                
                root.setOnClickListener {
                    mOnItemClickLister.onItemClicked(it,alarmModel)
                }

                tracker?.let {
                    if (it.isSelected(position.toLong()) )  {
                        it.select(position.toLong())
                        //changing the  color of the clicked/selected item to light gray
                        //parent.setBackgroundColor( ContextCompat.getColor(context,R.color.extra_light_gray))
                    } else {
                        it.deselect(position.toLong())
                        // set color white
                        //parent.setBackgroundColor( ContextCompat.getColor(context,R.color.white))
                    }
                }
            }
        }
    }

    private var tracker: SelectionTracker<Long>? = null

    fun setTracker(tracker: SelectionTracker<Long>?) {
        this.tracker = tracker
    }
}

解决方法

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