Saving RecyclerView state in a fragment when exiting it

Question

I am trying to make a app that sends messages to a recyclerView from fragment to another using a navgraph, but whenever I go back to my previous fragment to add a new message I lose the data of my recyclerView, and does not pile up.

---This is the kotlin code for the first fragment:

package com.example.passingdata

import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.EditText
import androidx.navigation.Navigation

private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"

class Fragment_A : Fragment() {
    // TODO: Rename and change types of parameters
    private var param1: String? = null
    private var param2: String? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        arguments?.let {
            param1 = it.getString(ARG_PARAM1)
            param2 = it.getString(ARG_PARAM2)
        }
    }

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


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

        val messageET = view.findViewById<EditText>(R.id.ETmessageTaker)
        val enterBTN = view.findViewById<Button>(R.id.BTNenter)

        enterBTN.setOnClickListener{
            val action = Fragment_ADirections.actionFragmentAToFragmentB(messageET.text.toString())
            Navigation.findNavController(view).navigate(action)

        }


    }


    companion object {
        fun newInstance(param1: String, param2: String) =
            Fragment_A().apply {
                arguments = Bundle().apply {
                    putString(ARG_PARAM1, param1)
                    putString(ARG_PARAM2, param2)
                }
            }
    }
}

---XML code for first fragment:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Fragment_A">

    <EditText
        android:id="@+id/ETmessageTaker"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:ems="10"
        android:hint="Message"
        android:inputType="textPersonName"
        android:minHeight="48dp"
        android:textSize="30sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/BTNenter"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:text="Enter"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ETmessageTaker" />
</androidx.constraintlayout.widget.ConstraintLayout>

---Kotlin code for second fragment :

package com.example.passingdata

import android.content.ContentValues.TAG
import android.os.Bundle
import android.os.Parcelable
import android.util.Log
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.navigation.Navigation
import androidx.navigation.fragment.navArgs
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.passingdata.databinding.FragmentBBinding
import messageAdapter

private const val ARG_PARAM1 = "param1"
private const val ARG_PARAM2 = "param2"
var state: Parcelable? = null

class Fragment_B : Fragment() {
    // TODO: Rename and change types of parameters
    private var param1: String? = null
    private var param2: String? = null
    private val args:Fragment_BArgs by navArgs()
    private var _binding: FragmentBBinding? = null
    private val binding get() = _binding!!

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        arguments?.let {
            param1 = it.getString(ARG_PARAM1)
            param2 = it.getString(ARG_PARAM2)
        }
    }

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        _binding = FragmentBBinding.inflate(inflater, container, false)
        return binding.root
    }


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


        val eachMessage = args.messageRecieved
        //putting words in TV
        binding.TVNewMessage.text = eachMessage

        //putting words in RV
        val messageList = mutableListOf(
            message(eachMessage)
        )
        val adapter = messageAdapter(messageList)
        binding.RVMessages.adapter = adapter
        binding.RVMessages.layoutManager = LinearLayoutManager(context)


        binding.BTNBack.setOnClickListener {
            Navigation.findNavController(view).navigate(R.id.action_fragment_B_to_fragment_A)
        }
    }



    companion object {
        fun newInstance(param1: String, param2: String) =
            Fragment_B().apply {
                arguments = Bundle().apply {
                    putString(ARG_PARAM1, param1)
                    putString(ARG_PARAM2, param2)
                }
            }
    }


    override fun onResume() {
        super.onResume()
        Log.d(TAG, "onResume Called")
        state = binding.RVMessages.layoutManager?.onSaveInstanceState();
    }

    override fun onPause() {
        super.onPause()
        Log.d(TAG, "onPause Called")
        state = binding.RVMessages.layoutManager?.onSaveInstanceState();

    }

    override fun onStop() {
        super.onStop()
        Log.d(TAG, "onStop Called")
        state = binding.RVMessages.layoutManager?.onSaveInstanceState();
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d(TAG, "onDestroy Called")
        _binding = null
    }
}

---XML code for second fragment:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Fragment_B">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/RV_messages"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginBottom="20dp"
        app:layout_constraintBottom_toTopOf="@+id/TV_newMessage"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/TV_newMessage"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="60dp"
        android:text="TextView"
        android:textSize="20sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/BTN_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp"
        android:layout_marginRight="10dp"
        android:text="Back"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/BTN_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp"
        android:text="Save"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent" />


</androidx.constraintlayout.widget.ConstraintLayout>

Someone suggested I override the 3 states and save them like this, but it did not work.
I even tried using SharedPrefrences but it gives me a error saying, "Unresolved reference: getSharedPrefrences".


override fun onResume() {
super.onResume()
Log.d(TAG, "onResume Called")
state = binding.RVMessages.layoutManager?.onSaveInstanceState();
}

override fun onPause() {
super.onPause()
Log.d(TAG, "onPause Called")
state = binding.RVMessages.layoutManager?.onSaveInstanceState();

}

override fun onStop() {
super.onStop()
Log.d(TAG, "onStop Called")
state = binding.RVMessages.layoutManager?.onSaveInstanceState();
}

Saving RecyclerView state in a fragment when exiting it

0 Answers0