Android Kotlin TextWatcher Usage

package com.googlecraft.textwatcher

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.text.Editable
import android.text.TextWatcher
import android.widget.Button
import android.widget.EditText

class MainActivity : AppCompatActivity() {
    lateinit var inputtext :EditText
    lateinit var action_button: Button

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        inputtext=findViewById(R.id.textinput)
        action_button=findViewById(R.id.button)


        inputtext.addTextChangedListener(object : TextWatcher
        {
            override fun afterTextChanged(p0: Editable?) {
            }

            override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            }

            override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            action_button.isEnabled=true
            }

        })

    }
}