android kotlin - Notification tap action example

MainActivity.kt

package com.cfsuman.kotlintutorials

import android.app.Activity
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.widget.Button
import androidx.core.app.NotificationCompat
import androidx.core.app.NotificationManagerCompat
import java.util.*


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

        // get the context
        val context = this

        // get the widgets reference from XML layout
        val button = findViewById<Button>(R.id.button)


        // Create and register notification channel api 26+
        val channelId = "My_Channel_ID"
        createNotificationChannel(channelId)


        // Create an explicit intent for an activity in this app
        val intent = Intent(this,MainActivity::class.java)

        intent.apply {
            flags = Intent.FLAG_ACTIVITY_NEW_TASK or
                    Intent.FLAG_ACTIVITY_CLEAR_TASK
        }

        val pendingIntent = PendingIntent.getActivity(
            context,0,intent,
            PendingIntent.FLAG_IMMUTABLE or
                    PendingIntent.FLAG_UPDATE_CURRENT
        )


        // button click listener
        button.setOnClickListener{
            val notificationBuilder = NotificationCompat
                .Builder(this,channelId)
                .setSmallIcon(R.drawable.ic_action_help)
                .setContentTitle("Title: API LEVEL " + Build.VERSION.SDK_INT)
                .setContentText("UUID: " + UUID.randomUUID())
                .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                .setContentIntent(pendingIntent)

            with(NotificationManagerCompat.from(this)){
                notify(1, notificationBuilder.build())
            }
        }
    }



    // create notification channel
    private fun createNotificationChannel(channelId:String) {
        // Create the NotificationChannel, but only on API 26+ (Android 8.0) because
        // the NotificationChannel class is new and not in the support library
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
            val name = "My Channel"
            val channelDescription = "Channel Description"
            val importance = NotificationManager.IMPORTANCE_DEFAULT

            val channel = NotificationChannel(channelId,name,importance)
            channel.apply {
                description = channelDescription
            }

            // Finally register the channel with system
            val notificationManager = getSystemService(
                Context.NOTIFICATION_SERVICE) as NotificationManager
            notificationManager.createNotificationChannel(channel)
        }
    }
}

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"
    android:background="#DCDCDC"
    android:id="@+id/rootLayout"
    android:padding="24dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Notification"
        android:textAllCaps="false"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

AndroidManifest.xml [Permission]

<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />