How to reflect changes in recycleview to parent activity?

Question

I created a recycleView in my main activity also, a textView which is use to display text if list passed to recycleView is empty. I have given a delete button on card of recycleView. When I open app and if list is empty then textView for empty view is visible and recycleView is invisible. But when I add some elements and delete all element then that textView for empty text is not visible. How can I resolve this?

Activity_main.xml

<?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=".MainActivity">

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:layout_width="57dp"
        android:layout_height="64dp"
        android:layout_marginEnd="40dp"
        android:layout_marginBottom="40dp"
        android:clickable="true"
        android:onClick="addNewCredentials"
        app:backgroundTint="@color/colorPrimary"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:srcCompat="@drawable/add"
        app:fabSize="normal"
        android:scaleType="center" />

    <TextView
        android:id="@+id/emptyView"
        android:layout_width="326dp"
        android:layout_height="71dp"
        android:gravity="center_horizontal|center_vertical"
        android:text="@string/empty_data"
        android:textAlignment="center"
        android:textAllCaps="true"
        android:textSize="30sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="@+id/recyclerView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="1dp"
        android:layout_marginTop="1dp"
        android:layout_marginEnd="1dp"
        android:layout_marginBottom="1dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0">

    </androidx.recyclerview.widget.RecyclerView>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

package com.example.passwordmanager
import android.content.Intent
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.TextView
import android.widget.Toast
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val recyclerView = findViewById<RecyclerView>(R.id.recyclerView)
        recyclerView.layoutManager = LinearLayoutManager(this, RecyclerView.VERTICAL,false)

        val db = DataBaseHandler(this)
        val detailsData = ArrayList(db.readCredentials())
        val adapter = CredentialAdapter(this,detailsData)
        recyclerView.adapter = adapter
        if(detailsData.isEmpty()){
            recyclerView.visibility = View.INVISIBLE
            findViewById<TextView>(R.id.emptyView).visibility = View.VISIBLE
        }
        else{
            recyclerView.visibility = View.VISIBLE
            findViewById<TextView>(R.id.emptyView).visibility = View.INVISIBLE
        }
    }


    fun addNewCredentials(view : View){
        print("hello world")
        val intent = Intent(this, AddDetailActivity::class.java)
        intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
        startActivity(intent)
    }
}

CredentialAdapter.kt

package com.example.passwordmanager

import android.content.ClipData
import android.content.ClipboardManager
import android.content.Context
import android.renderscript.RenderScript
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Button
import android.widget.TextView
import android.widget.Toast
import androidx.core.content.ContextCompat.getSystemService
import androidx.recyclerview.widget.RecyclerView
import android.content.Context.CLIPBOARD_SERVICE as CLIPBOARD_SERVICE1

//private var items: MutableList<CredentialsModel>,

class CredentialAdapter(ctx: Context, val credentialList : ArrayList<CredentialsModel>): RecyclerView.Adapter<CredentialAdapter.ViewHolder>() {
    var context = ctx

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val urlView = itemView.findViewById(R.id.urlView) as TextView
        val userNameView = itemView.findViewById(R.id.userNameView) as TextView
        val passwordView = itemView.findViewById(R.id.passwordView) as TextView
        val noteView = itemView.findViewById(R.id.noteView) as TextView
        val delButton = itemView.findViewById(R.id.delButton) as Button
        val cpyButton = itemView.findViewById(R.id.cpyButton) as Button
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(
            LayoutInflater.from(parent.context).inflate(R.layout.list_item_layout, parent, false)
        )
    }

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

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val credential: CredentialsModel = credentialList[position]
        holder.urlView.text = credential.url
        holder.userNameView.text = credential.userName
        holder.passwordView.text = credential.password
        holder.noteView.text = credential.note

        holder.delButton.setOnClickListener {
            val db = DataBaseHandler(context)
            if (db.deleteData(credential.id)) {
                credentialList.removeAt(holder.getAdapterPosition())
                notifyItemRemoved(position)
            }
        }

        holder.cpyButton.setOnClickListener {
            val clipboard = context.getSystemService(Context.CLIPBOARD_SERVICE) as ClipboardManager
            val clipUser = ClipData.newPlainText("username", credential.userName)
            clipboard.setPrimaryClip(clipUser)
            Toast.makeText(context, "Copied username to clipboard", Toast.LENGTH_SHORT).show()
            val clipPass = ClipData.newPlainText("password", credential.password)
            clipboard.setPrimaryClip(clipPass)
            Toast.makeText(context, "Copied password to clipboard", Toast.LENGTH_SHORT).show()
        }
    }
}

Answer 1

Easily check your list size in your delete function and make emptyText visible when the list size is zero. Sorry for Java code. Write this function in main activity

public void switchVisiblity(){
emptyTextView.setVisibility(View.VISIBLE);

}

Then call this method in the adapter delete function

holder.delButton.setOnClickListener {
        //write this below your code
        if(credentialList.size()==0){
           ((MainActivity)ctx).switchVisiblity();
       }
    }