Kotlin 在 Firebase 的类对象警告中找不到值的设置器/字段

Question

我正在尝试从我的Firebase数据库中获取ChatMessage数据类中的所有消息数据。在日志中，我可以看到数据确实在我的快照中获取，但它没有分配给数据类中的变量。我是 Kotlin & Firebase 的新手，所以我真的不明白为什么会这样？

在我进行了一些日志搜索后，我发现我一直收到此警告：

W/ClassMapper： no setter/field for -Llk34LtqGPJ3bwPrYRi 在class com.idiotboxes.socialowl.models.ChatMessage 上找到

在这里搜索了这个错误，发现它确实是一个非常普遍的问题。但是我的问题是，没有一个解决方案具有像我这样的数据类格式。

我知道警告是说我需要在我的数据类中设置 getter 和 setter，但我对 Kotlin 相当陌生，我不知道如何在我的数据类中实现 getter-setter。

以下是我的数据类聊天消息的外观：

package com.idiotboxes.socialowl.models
data class ChatMessage(val messageID: String, val fromID: String, val toID: 
String,val message: String, val timeStamp: Long){
//No argument constructor
constructor(): this("","","","",-1)
}

以下是我的 Firebase 数据库节点的外观： 数据库结构

编辑：这是额外的代码，可帮助您了解问题可能在哪里

我的回调接口

interface FirebaseCallback {
fun onCallback(latestMessage: ChatMessage)
}

我的函数从火库读取数据

private fun readFirebaseData(firebaseCallback: FirebaseCallback){
//Signed In user's ID
val fromID = FirebaseAuth.getInstance().uid
Log.w(TAG, "from ID is: $fromID (Currently Signed-In user)")
//Get Database Reference
val msgRef = FirebaseDatabase.getInstance().getReference("/Latest-messages/$fromID"/* Reference to current user's database entry */)
//Set a Listener for new messages
msgRef.addChildEventListener(object: ChildEventListener {
//adds new row when someone messages you for the first time, i.e. New Child is Added
override fun onChildAdded(p0: DataSnapshot, p1: String?) {
Log.w(TAG, "Snapshot captured from Firebase Database is: $p0")
//Convert snapshot to messages
//val latestMessage = p0.getValue(ChatMessage::class.java) ?: return
val callbackData: ChatMessage = p0.getValue(ChatMessage::class.java) ?: return
//TODO Implement Callback
firebaseCallback.onCallback(callbackData)
}
//Updates existing rows latest messages when user receives new message i.e. Latest Message child is Changed.
override fun onChildChanged(p0: DataSnapshot, p1: String?) {
val latestMessage: ChatMessage = p0.getValue(ChatMessage::class.java) ?: return//If Null then return
//Update the Existing row with new message
latestMessagesHashMap[p0.key!!] = latestMessage
updateRecyclerView()
}
--Some redundant methods of ChildEventListener--
})
latest_messages_recycler_view.adapter = adapter
//Recycler View Bottom Line Border
latest_messages_recycler_view.addItemDecoration(DividerItemDecoration(activity, DividerItemDecoration.VERTICAL))
}

我尝试从回调中检索数据的函数

private fun showLatestMessages(){
readFirebaseData(object : FirebaseCallback{
override fun onCallback(latestMessage: ChatMessage) {
//TODO latestMessage is  not null. But blank values are  being filled  in the Chat Message model class
Log.w(TAG, "NotNull latestMessage values are fromID: ${latestMessage.fromID} toID: ${latestMessage.toID} Typed Message: ${latestMessage.message} TimeStamp: ${latestMessage.timeStamp}")
//Add the new message row
adapter.add(LatestMessagesItems(latestMessage, context ?: return))
}
})
//Set OnClick Listener on Recycler View Items
adapter.setOnItemClickListener { item, view ->
//Grab the User details from the item that is clicked.
val userItem = item as LatestMessagesItems
//Start Chat Activity with the clicked User
val startChat = Intent(activity, ChatActivity::class.java)
startChat.putExtra(USER_KEY, userItem.recipientUser)
startActivity(startChat)
}
}
private fun updateRecyclerView(){
//Clear existing rows
adapter.clear()
//Fetch all Latest Messages from HashMap
latestMessagesHashMap.values.forEach {
adapter.add(LatestMessagesItems(it, context?: return))
}
}

我的回收器查看的"我的消息"项

class LatestMessagesItems(val latestMessage: ChatMessage, val ctx: Context): Item<ViewHolder>(){
lateinit var recipientUser: User
override fun getLayout(): Int {
return R.layout.latest_message_row
}
override fun bind(viewHolder: ViewHolder, position: Int) {
Log.w(TAG, "Fetched latest Message is: $latestMessage")
//Null Check
val recipientID: String? = if (latestMessage.fromID == FirebaseAuth.getInstance().uid) {
latestMessage.toID
} else {
latestMessage.fromID
}
//Fetch the recipient user details
val fetchRef = FirebaseDatabase.getInstance().getReference("/users/$recipientID")
fetchRef.addListenerForSingleValueEvent(object: ValueEventListener{
override fun onDataChange(p0: DataSnapshot) {
Log.w(TAG, "Fetched Recipient ID is: $recipientID")
//Fetch user details in User model class
recipientUser = p0.getValue(User::class.java) ?: return
Log.w(TAG, "Fetched Recipient User Name is: ${recipientUser.username}")
//Fill the User Details
viewHolder.itemView.recipient_username.text = recipientUser.username //Username
Glide.with(ctx).load(recipientUser.profileImage).into(viewHolder.itemView.recipient_profile_image) //Profile Pic
}
override fun onCancelled(p0: DatabaseError) {
}
})
//Latest Message Received
viewHolder.itemView.latest_received_message.text = latestMessage.message
}
}

最后，我根据此处发布的一些建议更新了我的模型类。 聊天消息.kt

package com.idiotboxes.socialowl.models
data class ChatMessage(var messageID: String? = null, var fromID: String? = null , var toID: String? = null ,var message: String? = null , var timeStamp: Long? = null){
//No argument constructor
constructor(): this("","","","",-1)
}

然而，问题仍然存在。

Answer 1

我不能肯定地说是这样，但我认为你应该写变量(var(，而不是值(val(。

这是因为 Kotlin 会自动生成var的 getter/setter，这被认为是可变的，而不是为val生成的

，它被认为是不可变的。私有变量也会发生同样的情况，因为 Kotlin 不会在本地范围之外为它们提供 getter/setter(例如，让 Firebase 访问它们(。