android kotlin - EditText live characters count

MainActivity.kt


package com.cfsuman.kotlintutorials

import android.app.Activity
import android.os.Bundle
import android.text.Editable
import android.text.InputFilter
import android.text.TextWatcher
import android.widget.EditText
import android.widget.TextView


class MainActivity : Activity() {
    private lateinit var editText:EditText
    private lateinit var textView:TextView

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

        // get the widgets reference from XML layout
        editText = findViewById(R.id.editText)
        textView = findViewById(R.id.textView)

        // set edit text max length to 10 programmatically
        val maxLength = 10
        editText.setMaxLength(maxLength)

        // add text changed listener to edit text
        editText.addTextChangedListener(object: TextWatcher {
            override fun beforeTextChanged(p0: CharSequence?,
                                           p1: Int, p2: Int, p3: Int) {

            }

            override fun onTextChanged(p0: CharSequence?,
                                       p1: Int, p2: Int, p3: Int) {
                // count number of inputted characters in edit text
                textView.text = "${p0?.toString()?.length}/$maxLength"
            }

            override fun afterTextChanged(p0: Editable?) {

            }
        })
    }
}


// extension function to set edit text maximum length
fun EditText.setMaxLength(maxLength: Int){
    filters = arrayOf<InputFilter>(
        InputFilter.LengthFilter(maxLength))
}

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"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="#DCDCDC"
    android:padding="32dp">

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginEnd="8dp"
        android:fontFamily="sans-serif-condensed-medium"
        android:inputType="text|textVisiblePassword"
        android:padding="12dp"
        android:textSize="25sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/textView"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.12" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:fontFamily="sans-serif-condensed-medium"
        android:textStyle="bold"
        android:gravity="center"
        android:padding="8dp"
        android:textColor="#4F42B5"
        android:textSize="25sp"
        app:layout_constraintBottom_toBottomOf="@+id/editText"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="@+id/editText"
        tools:text="TextView" />

</androidx.constraintlayout.widget.ConstraintLayout>

android kotlin - EditText live characters count