move activity content to fragment

activity_main.xml

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

    <FrameLayout
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

fragment_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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/edittext"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginHorizontal="24dp"
        android:hint="type me"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="Click Me"
        app:layout_constraintTop_toBottomOf="@+id/edittext"
        app:layout_constraintStart_toStartOf="@id/edittext"
        app:layout_constraintEnd_toEndOf="@id/edittext" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

package com.ascedncorp.androidbasic

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.ascedncorp.androidbasic.databinding.ActivityMainBinding

class MainActivity: AppCompatActivity() {

    private val binding: ActivityMainBinding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        if (savedInstanceState == null) {
            supportFragmentManager.beginTransaction()
                .replace(R.id.container, MainFragment.newInstance())
                .commit()
        }
    }
}

MainFragment.kt

package com.ascedncorp.androidbasic

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import com.ascedncorp.androidbasic.databinding.FragmentMainBinding

class MainFragment: Fragment() {

    private lateinit var binding: FragmentMainBinding

    companion object {
        fun newInstance() = MainFragment()
    }

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

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

        binding.button.setOnClickListener {
            startActivity(SecondActivity.newIntent(requireContext(), binding.edittext.text.toString()))
        }
    }
}