How to set a timer in Android using Kotlin?

This example demonstrates how to set a timer in Android using Kotlin.

Step 1 − Create a new project in Android Studio, go to File ? New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

Example

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:id="@+id/layout"
   android:layout_width="match_parent"
   android:layout_height="match_parent">
   <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerHorizontal="true"
      android:layout_marginTop="50dp"
      android:text="Tutorials Point"
      android:textAlignment="center"
      android:textColor="@android:color/holo_green_dark"
      android:textSize="32sp"
      android:textStyle="bold" />
   <Button
      android:id="@+id/button"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:onClick="startTimeCounter"
      android:text="Start Timer"
      android:textStyle="bold" />
   <TextView
      android:id="@+id/countTime"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_below="@id/button"
      android:layout_centerInParent="true"
      android:gravity="center"
      android:textColor="@android:color/background_dark"
      android:textSize="32sp" />
</RelativeLayout>

Step 3 − Add the following code to src/MainActivity.kt

example

import android.os.Bundle
import android.os.CountDownTimer
import android.view.View
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity
class MainActivity : AppCompatActivity() {
   var counter = 0
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
   }
   fun startTimeCounter(view: View) {
      val countTime: TextView = findViewById(R.id.countTime)
      object : CountDownTimer(50000, 1000) {
         override fun onTick(millisUntilFinished: Long) {
            countTime.text = counter.toString()
            counter++
         }
         override fun onFinish() {
            countTime.text = "Finished"
         }
      }.start()
   }
}

Step 4 − Add the following code to androidManifest.xml

Example

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q15">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen