android - kotlin.UninitializedPropertyAccessException : lateinit property roomClickedInterface has not been initialized

Question

我正在尝试按照 Pusher Chatkit 的 "BUILDING A GROUP CHAT APP USING KOTLIN AND PUSHER CHATKIT" 教程进行操作。但是我遇到了 Recycler View 适配器的问题。仅供引用，我仍在学习 Kotlin。我一直在阅读有关 lateinit vars 的内容，但找不到任何可以解决这种情况的内容。错误发生在回收器 View 适配器中。

这是我得到的错误:

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.android_myneighborsbookshelf, PID: 26692
    kotlin.UninitializedPropertyAccessException: lateinit property roomClickedInterface has not been initialized
        at com.example.android_myneighborsbookshelf.adapters.ChatRoomsListAdapter.getRoomClickedInterface(ChatRoomsListAdapter.kt:13)
        at com.example.android_myneighborsbookshelf.adapters.ChatRoomsListAdapter$ViewHolder.onClick(ChatRoomsListAdapter.kt:66)
        at android.view.View.performClick(View.java:6597)
        at android.view.View.performClickInternal(View.java:6574)
        at android.view.View.access$3100(View.java:778)
        at android.view.View$PerformClick.run(View.java:25885)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

ChatRoomsListActivity.kt

class ChatRoomsListActivity : AppCompatActivity() {
    val adapter = ChatRoomsListAdapter();

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_chat_room_list)
        initRecyclerView()
        initChatManager()
    }

    private fun initRecyclerView() {
        recycler_view.layoutManager = LinearLayoutManager(this@ChatRoomsListActivity)
        recycler_view.adapter = adapter
    }

    private fun initChatManager() {
        val chatManager = ChatManager(
                instanceLocator = "blahblahblah",
                userId = "username1-PCKid",
                dependencies = AndroidChatkitDependencies(
                        tokenProvider = ChatkitTokenProvider(
                                endpoint = "blahblahblah",
//                                endpoint = "http://10.0.2.2:3000/auth",
                                userId = "username1-PCKid"
                        )
                )
        )

        chatManager.connect(listeners = ChatListeners(
                onErrorOccurred = { },
                onAddedToRoom = { },
                onRemovedFromRoom = { },
                onCurrentUserReceived = { },
                onNewReadCursor = { },
                onRoomDeleted = { },
                onRoomUpdated = { },
                onPresenceChanged = { u, n, p -> },
                onUserJoinedRoom = { u, r -> },
                onUserLeftRoom = { u, r -> },
                onUserStartedTyping = { u, r -> },
                onUserStoppedTyping = { u, r -> }
        )) { result ->
            when (result) {
                is Result.Success -> {
                    // We have connected!
                    val currentUser = result.value
                    AppController.currentUser = currentUser
                    val userJoinedRooms = ArrayList<Room>(currentUser.rooms)
                    for (i in 0 until userJoinedRooms.size) {
                        adapter.addRoom(userJoinedRooms[i])
                    }

                    currentUser.getJoinableRooms { result ->
                        when (result) {
                            is Result.Success -> {
                                // Do something with List<Room>
                                val rooms = result.value
                                runOnUiThread {
                                    for (i in 0 until rooms.size) {
                                        adapter.addRoom(rooms[i])
                                    }
                                }
                            }
                        }
                    }

                    adapter.setInterface(object : ChatRoomsListAdapter.RoomClickedInterface {
                        override fun roomSelected(room: Room) {
                            if (room.memberUserIds.contains(currentUser.id)) {
                                // user already belongs to this room
                                roomJoined(room)
                            } else {
                                currentUser.joinRoom(
                                        roomId = room.id,
                                        callback = { result ->
                                            when (result) {
                                                is Result.Success -> {
                                                    // Joined the room!
                                                    roomJoined(result.value)
                                                }
                                                is Result.Failure -> {
                                                    Log.d("TAG", result.error.toString())
                                                }
                                            }
                                        }
                                )
                            }
                        }
                    })
                }

                is Result.Failure -> {
                    // Failure
                    Log.d("TAG", result.error.toString())
                }
            }
        }
    }

    private fun roomJoined(room: Room) {
        val intent = Intent(this@ChatRoomsListActivity, ChatRoomsListActivity::class.java)
        intent.putExtra("room_id", room.id)
        intent.putExtra("room_name", room.name)
        startActivity(intent)
    }
}

RecyclerView 适配器

import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import com.pusher.chatkit.rooms.Room
import android.view.LayoutInflater
import androidx.recyclerview.widget.RecyclerView
import com.example.android_myneighborsbookshelf.R

class ChatRoomsListAdapter: RecyclerView.Adapter<ChatRoomsListAdapter.ViewHolder>() {
    private var list = ArrayList<Room>()
    lateinit var roomClickedInterface:RoomClickedInterface // <-- Error occurs here - kt.13

    fun addRoom(room:Room){
        list.add(room)
        notifyDataSetChanged()
    }

    fun setInterface(roomClickedInterface:RoomClickedInterface){
        this.roomClickedInterface = roomClickedInterface
    }

    override fun getItemCount(): Int {
        return list.size
    }
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view = LayoutInflater.from(parent.context)
                .inflate(
                        android.R.layout.simple_list_item_1,
                        parent,
                        false
                )

        return ViewHolder(view)
    }


    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.roomName.text = list[position].name

    }

    inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView), View.OnClickListener {
        override fun onClick(p0: View?) {
            roomClickedInterface.roomSelected(list[adapterPosition]) // <-- Error occurs here kt.66
        }

        var roomName: TextView = itemView.findViewById(android.R.id.text1)

        init {
            itemView.setOnClickListener(this)
        }
    }

    interface RoomClickedInterface{
        fun roomSelected(room:Room)
    }
}

任何和所有的帮助表示赞赏。

Answer 1

lateinit means late initialization. If you do not want to initialize a variable in the constructor, instead you want to initialize it later on and if you can guarantee the initialization before using it, then declare that variable with lateinit keyword. It will not allocate memory until initialized.

所以，你必须初始化 lateinit属性，然后再尝试使用它。

选项 - 1:调用 setInterface()在单击列表项之前初始化属性。您还可以检查 lateinit var 已经初始化或未使用 .isInitialized如下所示:

override fun onClick(p0: View?) {

    if(this::roomClickedInterface.isInitialized) {
        roomClickedInterface.roomSelected(list[adapterPosition])
    }
}

选项 - 2:删除 lateinit来自您的适配器的属性，也是它的 setter

//lateinit var roomClickedInterface:RoomClickedInterface

并通过 RoomClickedInterface作为适配器构造函数的参数

class ChatRoomsListAdapter(val roomClickedInterface:RoomClickedInterface):
     RecyclerView.Adapter<ChatRoomsListAdapter.ViewHolder>() {

    //Implementation
}

选项 - 3:删除 lateinit并使用 nullable属性(property)

private var roomClickedInterface: RoomClickedInterface? = null

然后像下面一样使用 null安全符号 ?. :

override fun onClick(p0: View?) {
    roomClickedInterface?.roomSelected(list[adapterPosition])
}