无法使用带有自定义适配器的回收器视图显示Firebase实时数据库中的消息列表

Question

我正在尝试使用android中的Recyler视图显示用户发送到实时Firebase数据库的消息，但是即使更新Firebase数据库，我的聊天屏幕仍显示空白屏幕。

这是MainChatActivity.kt文件

.add()

这是我用于回收者视图的Adapter.kt文件

var selector = ".a .b .c ";
var parts = [ ".c2", ".c3" ];

var jq = null;
$.each(parts, function(i, val) {
  if (jq == null)
      jq = $(selector + val);
  else
      jq.add(selector + val);
});
jq.hide();

这是用于存储来自firebase Messages.kt类的datasnapshot的消息的类

class MainChatActivity : AppCompatActivity() {

var mDisplayName:String?=null

var databaseref:DatabaseReference?=null
var msgEditText:EditText?=null
var sendButton:ImageButton?=null
var msgRow:RecyclerView?=null

var Adapter:Adapter?=null
var viewManager: RecyclerView.LayoutManager?=null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main_chat)

    msgEditText = findViewById(R.id.messageInput)
    sendButton=findViewById(R.id.sendButton)

    msgRow=findViewById<RecyclerView>(R.id.chat_list_view)


    Adapter = Adapter(databaseref,mDisplayName,this@MainChatActivity)
    viewManager = LinearLayoutManager(this@MainChatActivity)
    msgRow?.apply {
        layoutManager=viewManager
        adapter=Adapter
        itemAnimator=DefaultItemAnimator()
    }

}

override fun onResume() {
    super.onResume()

    databaseref=FirebaseDatabase.getInstance().getReference()

    msgEditText?.setOnEditorActionListener(TextView.OnEditorActionListener { v, actionId, event ->
        sendMessage(msgEditText?.text.toString())
        true
    })

    sendButton?.setOnClickListener {
        sendMessage(msgEditText?.text.toString())
    }
}

private fun sendMessage(message: String) {

    if (message != "") {
        val prefs: SharedPreferences = this@MainChatActivity.getSharedPreferences(RegisterActivity.static.myPrefs, 0)
        mDisplayName=prefs.getString("DisaplayName","DisaplayName")
        Log.v("displaynamechat",mDisplayName.toString())
        if(prefs.getString("DisaplayName",null) =="")
        {
            mDisplayName="Anonymous"
        }
        val chat = Messages(message, mDisplayName.toString())
        databaseref?.child("messages")?.push()?.setValue(chat)
        msgEditText?.setText("")
    }

}

public override fun onStart() {
    super.onStart()

}

override fun onStop() {
    super.onStop()
    Adapter?.cleanup()
}
}

activity_main_chat.xml

class Adapter (databaseRef: DatabaseReference?, displayName: String?, context: Context): RecyclerView.Adapter<Adapter.viewHolder>(){

var databaseRef:DatabaseReference?=null
var author:String?=null
var context:Context?=null
lateinit var dataSnap:ArrayList<DataSnapshot>

private val mListener = object : ChildEventListener {
    override fun onChildAdded(dataSnapshot: DataSnapshot, s: String?) {

        dataSnap.add(dataSnapshot)
        notifyDataSetChanged()
    }

    override fun onChildChanged(dataSnapshot: DataSnapshot, s: String?) {

    }

    override fun onChildRemoved(dataSnapshot: DataSnapshot) {

    }

    override fun onChildMoved(dataSnapshot: DataSnapshot, s: String?) {

    }

    override fun onCancelled(databaseError: DatabaseError) {

    }
}

init {
    this.databaseRef=databaseRef?.child("messages")
    this.author=displayName
    this.context=context
    this.dataSnap = java.util.ArrayList<DataSnapshot>()
    this.databaseRef?.addChildEventListener(this.mListener)
}

override fun onCreateViewHolder(p0: ViewGroup, p1: Int): viewHolder {
    var itemvew= LayoutInflater.from(p0.context)
        .inflate(R.layout.chat_msg_row,p0,false)
    return viewHolder(itemvew)

}

override fun getItemCount(): Int {
    return dataSnap.size
}

override fun onBindViewHolder(p0: viewHolder, p1: Int) {
    var gettingcurrentSnap= dataSnap.get(p0.adapterPosition)

    var meessageClass = gettingcurrentSnap.getValue(Messages::class.java)

    Log.v("flashchat message",meessageClass?.msg)

    p0.msgText?.setText(meessageClass?.msg)
    if(author =="")
        author="Anonymous"

    p0.author?.setText(meessageClass?.author)

    if (meessageClass?.author == author) {
        p0.body?.setBackgroundResource(R.drawable.bubble2)
        p0.body?.gravity = Gravity.END
        p0.author?.setTextColor(Color.GREEN)
    }
    else
    {
        p0.body?.setBackgroundResource(R.drawable.bubble1)
        p0.body?.gravity = Gravity.START
        p0.author?.setTextColor(Color.BLUE)
    }
}

class viewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    var msgText: TextView?=null
    var author: TextView?=null
    var body:LinearLayout?=null

    init {
        msgText=itemView.findViewById(R.id.message)
        author=itemView.findViewById(R.id.author)
        body=itemView.findViewById(R.id.singleMessageContainer)
    }
}

internal fun cleanup() {

    databaseRef?.removeEventListener(mListener)
}

}

chat_msg_row.xml

class Messages {
var author: String=""
var msg: String=""

private constructor() {}

constructor(author: String, text: String) {
    this.author = author
    this.msg = text
}
}