How to display count of notifications in the Android App launcher using Kotlin?

This example demonstrates how to display count of notifications in the Android App launcher 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.

<?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"
   tools:context=".MainActivity">
   <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:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:onClick="createNotification"
      android:text="create notification" />
</RelativeLayout>

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

import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import android.os.Build
import android.os.Bundle
import android.view.View
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.NotificationCompat
class MainActivity : AppCompatActivity() {
   var count = 0
   private val channelId = "10001"
   private val defaultChannelId = "default"
   override fun onResume() {
      super.onResume()
      count = 0
   }
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
   }
   fun createNotification(view: View) {
      count++
      val notificationIntent = Intent(applicationContext, MainActivity::class.java)
      notificationIntent.putExtra("fromNotification", true)
      notificationIntent.flags = Intent.FLAG_ACTIVITY_CLEAR_TOP or
      Intent.FLAG_ACTIVITY_SINGLE_TOP
      val pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0)
      val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as
      NotificationManager
      val builder = NotificationCompat.Builder(applicationContext, defaultChannelId)
      builder.setContentTitle("My Notification")
      builder.setContentIntent(pendingIntent)
      builder.setContentText("Notification Listener Service Example")
      builder.setSmallIcon(R.drawable.ic_launcher_foreground)
      builder.setAutoCancel(true)
      builder.setBadgeIconType(NotificationCompat.BADGE_ICON_SMALL)
      builder.setNumber(count)
      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
         val importance = NotificationManager.IMPORTANCE_HIGH
         val notificationChannel = NotificationChannel(channelId,
         "NOTIFICATION_CHANNEL_NAME", importance)
         builder.setChannelId(channelId)
         notificationManager.createNotificationChannel(notificationChannel)
      }
      notificationManager.notify(System.currentTimeMillis().toInt(), builder.build())
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q11">
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
   <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