【ANDROID STUDIO】Data Binding

 package com.example.simplebinding

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import com.example.simplebinding.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.submitButton.setOnClickListener {
            displayGreeting()
        }
    }


    private fun displayGreeting() {
        binding.apply {
            greetingTextView.text = "Hello! " + nameEditText.text
        }

    }
}

<?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:id="@+id/nameText"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MainActivity">

        <TextView
            android:id="@+id/greetingTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="30sp"
            android:textStyle="bold"
            android:typeface="sans"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintHorizontal_bias="0.532"
            app:layout_constraintLeft_toLeftOf="parent"
            app:layout_constraintRight_toRightOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.175" />

        <EditText
            android:id="@+id/nameEditText"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_margin="20dp"
            android:ems="10"
            android:hint="@string/insert_you_name_here"
            android:inputType="textPersonName"
            android:textSize="30sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/greeting_text_view"
            app:layout_constraintVertical_bias="0.126" />

        <Button
            android:id="@+id/submit_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/submit"
            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="0.613" />

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