【ANDROID STUDIO】Data Binding Show or Hide Progressbar

 package com.example.databinding

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import androidx.databinding.DataBindingUtil
import com.example.databinding.databinding.ActivityMainBinding
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)

        binding.controlButton.setOnClickListener {
            startOrStopProgressBar()
        }
    }

    private fun startOrStopProgressBar() {
        binding.apply {
            if (progressBar.visibility == View.GONE) {
                progressBar.visibility = View.VISIBLE
                controlButton.text = "Stop"
            } else {
                progressBar.visibility = View.GONE
                controlButton.text = "Start"
            }
        }

    }

}

<?xml version="1.0" encoding="utf-8"?>
<layout 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">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">


        <ProgressBar android:id="@+id/progressBar"
        style="@android:style/Widget.DeviceDefault.Light.ProgressBar.Large"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"

            android:visibility="gone"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.471"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.295" />

        <Button android:id="@+id/controlButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Start"
            android:textSize="30sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.498"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.557" />

    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>