Problem in retrieving chat message from firebase

Question

I am trying to build a chatting application but whenever I click on the any of the users it crashes.

class MessegeActivity : AppCompatActivity() {

    var userIdVisit: String = ""
    var currentUserId : FirebaseUser?=null
    var chatsAdpater:ChatAdpater?=null
    var mChatList:List<Chat>?=null
    lateinit var recycler_view_chat:RecyclerView


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

        intent = intent
        userIdVisit = intent.getStringExtra("visit_id")
        currentUserId =FirebaseAuth.getInstance().currentUser!!

        recycler_view_chat =findViewById(R.id.recycler_view_chat)
        recycler_view_chat.setHasFixedSize(true)
        var linearLayoutManager =LinearLayoutManager(applicationContext)
        linearLayoutManager.stackFromEnd =true
        recycler_view_chat.layoutManager =linearLayoutManager

        //showing other username and profile dp

        val reference = FirebaseDatabase.getInstance().reference
            .child("Users").child(userIdVisit)

        reference.addValueEventListener(object : ValueEventListener {
            override fun onDataChange(p0: DataSnapshot) {
                val user: Users? = p0.getValue(Users::class.java)

                username_mchat.text = user!!.getFullName()
                Picasso.get().load(user.getImg()).into(profile_image_mchat)

                retreiveMsg(currentUserId!!.uid,userIdVisit,user.getImg())

            }

            override fun onCancelled(error: DatabaseError) {

            }
        })


        send_messege_btn.setOnClickListener {
            val messege = text_messege.text.toString()
            if (messege == "") {
                Toast.makeText(this@MessegeActivity, "Please write something!!", Toast.LENGTH_SHORT)
                    .show()
            } else {
                sendMessegeToUser(currentUserId!!.uid, userIdVisit, messege)
            }
            text_messege.setText("")
        }

        attach_image_file.setOnClickListener {
            val intent = Intent()
            intent.action = Intent.ACTION_GET_CONTENT
            intent.type = "image/*"
            startActivityForResult(Intent.createChooser(intent, "Pick Image"), 198)
        }

    }


    private fun sendMessegeToUser(senderId: String, receiverId: String?, messege: String) {

        val reference = FirebaseDatabase.getInstance().reference
        val messegeKey:String = reference.push().key!!

        val messegeHashMap = HashMap<String, Any?>()
        messegeHashMap["sender"] = senderId
        messegeHashMap["messege"] = messege
        messegeHashMap["receiver"] = receiverId
        messegeHashMap["isseen"] = "false"
        messegeHashMap["url"] = ""
        messegeHashMap["messegeId"] = messegeKey
        reference.child("Chats").child(messegeKey).setValue(messegeHashMap)
            .addOnCompleteListener { task ->
                if (task.isSuccessful) {
                    val ChatsListRefernce =
                        FirebaseDatabase.getInstance().reference.child("ChatLists").child(currentUserId!!.uid).child(userIdVisit)

                    ChatsListRefernce.addListenerForSingleValueEvent(object :ValueEventListener{
                        override fun onDataChange(p0: DataSnapshot) {
                            if(!p0.exists())
                            {
                                ChatsListRefernce.child("id").setValue(userIdVisit)
                            }

                            val ChatsListReceiverRefernce =
                                FirebaseDatabase.getInstance().reference.child("ChatLists").child(userIdVisit).child(currentUserId!!.uid)
                            ChatsListReceiverRefernce.child("id").setValue(currentUserId!!.uid)


                        }

                        override fun onCancelled(error: DatabaseError) {

                        }
                    })


                    //notification


                //    val reference = FirebaseDatabase.getInstance().reference
                   //     .child("Users").child(currentUserId!!.uid)


                }
            }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)

        if (requestCode == 198 && resultCode ==RESULT_OK && data!=null && data.data != null) {
            val progressBar = ProgressDialog(this)
            progressBar.setMessage("Please wait")
            progressBar.show()

            val fileUri = data.data
            val storageRef = FirebaseStorage.getInstance().reference.child("Chat Images")
            val ref = FirebaseDatabase.getInstance().reference
            val messegeId = ref.push().key
            val filepath = storageRef.child("$messegeId.jpg")

            var uploadTask: StorageTask<*>
            uploadTask = filepath.putFile(fileUri!!)

            uploadTask.continueWithTask(Continuation<UploadTask.TaskSnapshot, Task<Uri>> { task ->
                if (!task.isSuccessful) {
                    task.exception?.let {
                        throw it
                    }
                }
                return@Continuation filepath.downloadUrl
            }).addOnCompleteListener { task ->
                val downloadUrl = task.result
                val url = downloadUrl.toString()

                val messegeHashMap = HashMap<String,Any?>()
                messegeHashMap["sender"] = currentUserId!!.uid
                messegeHashMap["messege"] = "sent you an image"
                messegeHashMap["receiver"] = userIdVisit
               messegeHashMap["isseen"] = "false"
                messegeHashMap["url"] = url
                messegeHashMap["messegeId"] = messegeId.toString()

                ref.child("Chats").child(messegeId!!).setValue(messegeHashMap)

                progressBar.dismiss()
            }
        }
    }

    private fun retreiveMsg(senderId: String, receiverId: String?, recieverimgUrl: String?) {
        mChatList =ArrayList()
        val reference =FirebaseDatabase.getInstance().reference.child("Chats")

        reference.addValueEventListener(object:ValueEventListener{
            override fun onDataChange(p0: DataSnapshot) {
                (mChatList as ArrayList<Chat>).clear()
                for (snapshot in p0.children)
                {
                    val chat= snapshot.getValue(Chat::class.java)
                    if(chat!!.getReceiver().equals(senderId)&& chat.getSender().equals(receiverId) ||
                        chat.getReceiver().equals(receiverId)&& chat.getSender().equals(senderId))
                    {
                        (mChatList as ArrayList<Chat>).add(chat)
                    }
                    chatsAdpater = ChatAdpater(this@MessegeActivity,(mChatList as ArrayList<Chat>),recieverimgUrl!!)
                    recycler_view_chat.adapter =chatsAdpater
                }

            }

            override fun onCancelled(error: DatabaseError) {
                TODO("Not yet implemented")
            }
        })

    }

    }


   




    package com.insidecoderz.trails2.Model
    class Chat {
    private var sender:String =""
    private var messege:String =""
    private var receiver:String =""
    private var isseen :Boolean= false
    private var url:String =""
    private var messegeId:String =""

    constructor()
    constructor(
        sender: String,
        messege: String,
        receiver: String,
        isseen:Boolean,
        url: String,
        messegeId: String
    ) {
        this.sender = sender
        this.messege = messege
        this.receiver = receiver
        this.isseen = isseen
        this.url = url
        this.messegeId = messegeId
    }

    fun getSender(): String?{
        return sender
    }
    fun setSender(sender: String){
        this.sender =sender
    }

    fun getMessege(): String?{
        return messege
    }
    fun setMessege(messege: String){
        this.messege =messege
    }

    fun getReceiver(): String?{
        return receiver
    }
    fun setReceiver(receiver: String){
        this.receiver =receiver
    }

    fun isIsSeen(): Boolean {
        return isseen
    }
    fun setIsSeen(isseen: Boolean){
        this.isseen =isseen
    }

    fun getUrl(): String?{
        return url
    }
    fun setUrl(url: String){
        this.url =url
    }
   fun getMessegeId(): String?{
        return messegeId
    }
    fun setMessegeId(messegeId: String){
        this.messegeId =messegeId
    }

}

I am facing this issue again and again, whenever I run the application in the application in the emulator it crashes with showing this error.

2020-08-22 23:19:59.920 17005-17005/com.insidecoderz.trails2 E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.insidecoderz.trails2, PID: 17005
com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.Boolean to type com.insidecoderz.trails2.Model.Chat
    at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:435)
    at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:231)
    at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:79)
    at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
    at com.insidecoderz.trails2.MessegeActivity$retreiveMsg$1.onDataChange(MessegeActivity.kt:202)
    at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)
    at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63)
    at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:224)
    at android.app.ActivityThread.main(ActivityThread.java:7134)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:536)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:876)

Answer 1

If you access the id of the user with the following code val reference = FirebaseDatabase.getInstance().reference.child("Users").child(userIdVisit) and then you try to get the data as a model Chat you can not do that, instead try FirebaseDatabase.getInstance().reference.child("Users").This way you'll be able to get your data as model Chat but it won't be the id you want, also if at the node "Users" you have more users then you'll obtain all the users info using the model Chat

If you need the information for the userIdVisit then you can you do the following

snapshot.child("userInfo1").getValue();
snapshot.child("userInfo2").getValue();

This is the sample for java, you should adapt it for kotlin, I'm sorry for not providing the sample in kotlin but I'm not familiar with it