尽管进行了初始化，但在 Fragment 中还没有初始化 lateinit 属性

Question

问候， 我有一个从 Firestore 中提取数据的 FirestoreRecyclerAdapter。在提取数据之前，我想展示一个方便工作的骨架视图。为了在拉取数据时通知 Fragment，我使用了一个侦听器。但是，当我在 Fragment 中覆盖此侦听器接口的方法时，由于某种原因，我的 recyclerView 得到“kotlin.UninitializedPropertyAccessException：lateinit 属性 rvShops 尚未初始化”，即使它们在触发接口方法时已初始化.我的代码sn-ps如下：

class ShopsFragment : Fragment(), ShopsLoadedListener {
companion object {
    fun newInstance(): ShopsFragment {
        return ShopsFragment()
    }
}

private lateinit var colRefShops: CollectionReference
private lateinit var shopAdapter: ShopAdapter
private lateinit var v: View
private lateinit var b: FragmentShopsBinding
private lateinit var skeleton: Skeleton

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    arguments?.let {
    }
    (activity as MainActivity).tabLayoutShops.visibility = View.GONE
    colRefShops = FirebaseFirestore.getInstance().collection(DB_SHOPS)

}

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    v = inflater.inflate(R.layout.fragment_shops, container, false)
    return v
}


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

  override fun onStart() {
    super.onStart()
    shopAdapter.startListening()
}

private fun initRecyclerView() {
    rvShops?.layoutManager = GridLayoutManager(v.context, 2)
    skeleton = skelOutShops
    skeleton = rvShops.applySkeleton(R.layout.item_shop, 10)
    skeleton.showSkeleton()

    val q: Query = colRefShops.orderBy(WEIGHT)
    val options: FirestoreRecyclerOptions<ModelShop> =
        FirestoreRecyclerOptions.Builder<ModelShop>()
            .setQuery(q, ModelShop::class.java)
            .build()
    shopAdapter = ShopAdapter(options, shopsLoadedListener = newInstance())

}

override fun onStop() {
    super.onStop()
    shopAdapter.stopListening()
}

override fun onShopsLoaded(i: Int) {

    Log.d("dataComes", "Data = $i")
    rvShops.adapter = shopAdapter //here i get kotlin.UninitializedPropertyAccessException: lateinit property rvShops has not been initialized when this method is fired up
    skeleton.showOriginal()
}
}

---

我的适配器：

class ShopAdapter(options: FirestoreRecyclerOptions<ModelShop>, private var shopsLoadedListener: ShopsLoadedListener)
: FirestoreRecyclerAdapter<ModelShop, ShopAdapter.ShopViewHolder>(options) {

override fun onDataChanged() {
    super.onDataChanged()
    shopsLoadedListener.onShopsLoaded(5)
}

private var v: View? = null
public interface ShopsLoadedListener{
    fun onShopsLoaded(i: Int)
}


class ShopViewHolder(private val b: ItemShopBinding) : RecyclerView.ViewHolder(b.root)

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ShopViewHolder {
    val layoutInflater = LayoutInflater.from(parent.context)
    val v = layoutInflater.inflate(R.layout.item_shop, parent, false)
    val b = ItemShopBinding.inflate(layoutInflater)
    Log.d("fire", "ifireincreateviewholder")

    return ShopViewHolder(b)
}

 override fun onBindViewHolder(vHolder: ShopViewHolder, i: Int, modelShop: ModelShop) {
    vHolder.itemView.tvShopName.text = modelShop.displayName
     Glide.with(vHolder.itemView.context)
         .load(modelShop.logoURL)
         .centerCrop()
         .into(vHolder.itemView.ivShopLogo)
}
}

Answer 1

错误消息告诉您在分配值之前尝试使用skeleton。几乎可以肯定，onShopsLoaded 在initRecyclerView 可以初始化之前被调用。您将不得不编写代码来检测这种情况并正确处理它。

Answer 2

据我所知，您永远不会将 rvShops 分配给任何东西，这会导致它未初始化。鉴于它设置为lateinit，因此您获得UninitializedPropertyAccessException 是有道理的。

解决方案：

在您的片段中分配onViewCreated(...) 中的rvShops，这不应该再像那样崩溃了。

Answer 3

private fun initRecyclerView() {
rvShops?.layoutManager = GridLayoutManager(v.context, 2)
skeleton = skelOutShops
skeleton = rvShops.applySkeleton(R.layout.item_shop, 10)
skeleton.showSkeleton()

val q: Query = colRefShops.orderBy(WEIGHT)
val options: FirestoreRecyclerOptions<ModelShop> =
    FirestoreRecyclerOptions.Builder<ModelShop>()
        .setQuery(q, ModelShop::class.java)
        .build()
shopAdapter = ShopAdapter(options, shopsLoadedListener = newInstance())
}

原来问题出在这个函数上，尤其是这一行：

shopAdapter = ShopAdapter(options, shopsLoadedListener = newInstance())

创建这个监听器实例的正确方法应该是：

shopAdapter = ShopAdapter(options, this)

在这种情况下，我实现的方法也可以正常工作。