How to make a Countdown Timer in Android using Kotlin

Last updated on: May 27, 2023

Today, I will show you how to build a timer that countdowns until an event (e.g. new year’s day or the release date of a video game) using the Handler to update the TextView every second.

First, add a TextView in your layout, like that:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorPrimaryDark"
    tools:context=".MainActivity">
    <TextView
        android:id="@+id/countdown_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="10d 7h 15m 15s"
        android:textColor="@android:color/white"
        android:textSize="30sp"
        android:textStyle="bold" />
</RelativeLayout>Code language: HTML, XML (xml)

Then go to your Activity and create a method with a name updateTime() and set the current date:

fun updateTime() {
        // Set Current Date
        val currentDate = Calendar.getInstance()
    }Code language: Kotlin (kotlin)

Set the event date

fun updateTime() {
        // ...
        // Set Event Date
        val eventDate = Calendar.getInstance()
        eventDate[Calendar.YEAR] = 2023
        eventDate[Calendar.MONTH] = 0 // 0-11 so 1 less
        eventDate[Calendar.DAY_OF_MONTH] = 1
        eventDate[Calendar.HOUR] = 0
        eventDate[Calendar.MINUTE] = 0
        eventDate[Calendar.SECOND] = 0
        eventDate.timeZone = TimeZone.getTimeZone("GMT")
        // ...
    }Code language: Kotlin (kotlin)

Find how many milliseconds left until the event

fun updateTime() {
        // ...
        // Find how many milliseconds until the event
        val diff = eventDate.timeInMillis - currentDate.timeInMillis
        // ...
    }Code language: Kotlin (kotlin)

Convert the milliseconds to days, hours, minutes, and seconds

fun updateTime() {
        // ...
        
        // Change the milliseconds to days, hours, minutes and seconds
        val days = diff / (24 * 60 * 60 * 1000)
        val hours = diff / (1000 * 60 * 60) % 24
        val minutes = diff / (1000 * 60) % 60
        val seconds = (diff / 1000) % 60
        // ...
    }Code language: Kotlin (kotlin)

Show the countdown timer in your TextView

fun updateTime() {
        // ...
        
        // Display Countdown
        countdownText.text = "${days}d ${hours}h ${minutes}m ${seconds}s"

        // ...

    }Code language: Kotlin (kotlin)

Now, to call the updateTime() method every second, we’re going to use the Handler() class and repeat the handler every second (1000 milliseconds)

private lateinit var countdownText: TextView

private val handler = Handler(Looper.getMainLooper())

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

        countdownText = findViewById(R.id.countdown_text)

        // Update TextView every second
        handler.post(object : Runnable {
            override fun run() {
                // Keep the postDelayed before the updateTime(), so when the event ends, the handler will stop too.
                handler.postDelayed(this, 1000)
                updateTime()
            }
        })
    }Code language: Kotlin (kotlin)

If you want to show different text after the event has passed, create a method with the name endEvent and pass the currentDate and eventDate.

After you have shown your text, stop the handler from repeating it.

fun updateTime() {

        // ...

        // Show different text when the event has passed
        endEvent(currentDate, eventDate)
    }

    private fun endEvent(currentDate: Calendar, eventDate: Calendar) {
        if (currentDate.time >= eventDate.time) {
            countdownText.text = "Happy New Year!"

            // Stop Handler
            handler.removeMessages(0)
        }
    }Code language: Kotlin (kotlin)

Done!

You can find the final project here

If you have any questions, please feel free to leave a comment below