How to add TextWatcher Listener to EditText in Kotlin

In this android kotlin source code example, we are going to add TextWatcher Listener to EditText in Kotlin.

You can copy and adopt this source code example to your Kotlin android project without reinventing the wheel.

Below is a step by step source code to add TextWatcher Listener to EditText in Kotlin.

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=".EditText.EditTextActivity17">

    <TextView
        android:id="@+id/textWatcher"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Text watcher"
        android:gravity="center"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <EditText
        android:id="@+id/edtField"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Text"
        app:layout_constraintTop_toBottomOf="@id/textWatcher"/>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.EditText
import android.widget.TextView
import com.bluapp.kotlinview.R
import androidx.databinding.adapters.TextViewBindingAdapter.setText
import android.text.Editable
import android.text.TextWatcher



class EditTextActivity17 : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_edit_text17)
        val textWatcher = findViewById<TextView>(R.id.textWatcher) as TextView
        val edtField = findViewById<EditText>(R.id.edtField) as EditText
        edtField.addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(charSequence: CharSequence, i: Int, i1: Int, i2: Int) {
            }
            override fun onTextChanged(charSequence: CharSequence, i: Int, i1: Int, i2: Int) {
            }
            override fun afterTextChanged(editable: Editable) {
                textWatcher.text = edtField.text.toString()
            }
        })
    }
}

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