How to Push Notification in Android?

Notification is a message which appears outside of our Application’s normal UI. A notification can appear in different formats and locations such as an icon in the status bar, a more detailed entry in the notification drawer, etc. Through the notification, we can notify users about any important updates, events of our application. By clicking the notification user can open any activity of our application or can do some action like opening any webpage etc. 

How Does Notification Look?

Let see the basic design of a notification template that appears in the navigation drawer. 

Part of a Notification	Method for defining contents	Type of argument needs to pass into the method
Small Icon	setSmallIcon()	need to pass a drawable file as an ID that is an Int type.
App Name	By default, App Name is provided by the System and we can’t override it.
Time Stamp	By default, timeStamp is provided by the System but we can override it by setWhen() method.	A Long type of data should be passed.
Title	setContentTitle()	A String type of data should be passed.
Text	setContentText()	A String type of data should be passed.
Large Icon	setLargeIcon()	A Bitmap! type image file data should be passed.

Understand Some Important Concepts of Push a Notification

We shall discuss all the concepts mentioned below step by step,

1. Creating a basic notification
2. Creating notification channel
3. Adding large icon
4. Making notification expandable
5. Making notification clickable
6. Adding an action button to our notification

1. Creating a basic notification 

To create a basic notification at first we need to build a notification. Now to build notification, we must use NotificationCompat.Builder() class where we need to pass a context of activity and a channel id as an argument while making an instance of the class. Please note here we are not using Notification.Builder(). NotificationCompat gives compatibility to upper versions (Android 8.0 and above) with lower versions (below Android 8.0).

Kotlin

val nBuilder = NotificationCompat.Builder(this,CHANNEL_ID)
                    .setContentTitle(et1.text.toString())
                    .setContentText(et2.text.toString())
                    .setSmallIcon(R.drawable.spp_notification_foreground)
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                    .build()

Please note, here we need to set the priority of the notification accordingly by the setPriority() method.

Now to deliver the notification we need an object of NotificationManagerCompat class and then we notify it.

Kotlin

val nManager = NotificationManagerCompat.from(this)
// Here we need to set an unique id for each
// notification and the notification Builder
            nManager.notify(1, nBuilder)

Please note that, in this method, we can deliver notification only in the android versions below 8.0 but in the android versions 8.0 and upper, no notification will appear by only this block of code.

2. Creating a notification channel

Now to deliver notifications on android version 8.0 and above versions, we need to create a notification channel. This  Notification Channel concept comes from android 8.0. Here every application may have multiple channels for different types of notifications and each channel has some type of notification. Before you can deliver the notification on Android 8.0 and above versions, you must register your app’s notification channel with the system by passing an instance of NotificationChannel to createNotificationChannel().

Kotlin

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            val channel = NotificationChannel(CHANNEL_ID, CHANNEL_NAME, NotificationManager.IMPORTANCE_DEFAULT).apply {
                description = CHANNEL_DESCRIPTION
            }
            val nManager: NotificationManager =
            getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            nManager.createNotificationChannel(channel)
        }

Please note that here we must provide a unique CHANNEL_ID for each channel and also we must give a CHANNEL_NAME and CHANNEL_DESCRIPTION. Also, we must give channel importance.

3. Adding a large icon

To set a large icon we use the setLargeIcon() method which is applied to the instance of the NotificationCompat.Builder() class. In this method, we need to pass a Bitmap form of an image. Now to convert an image file (e.g. jpg, jpeg, png, etc.)  of the drawable folder into a Bitmap, we use the following code in Kotlin

Kotlin

// converting a jpeg file to Bitmap file and making an instance of Bitmap!
val imgBitmap=BitmapFactory.decodeResource(resources,R.drawable.gfg_green)

// Building notification
val nBuilder= NotificationCompat.Builder(this,CHANNEL_ID)
                    .setContentTitle(et1.text.toString())
                    .setContentText(et2.text.toString())
                    .setSmallIcon(R.drawable.spp_notification_foreground)
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                    // passing the Bitmap object as an argument
                    .setLargeIcon(imgBitmap)
                    .build()

4. Making notification expandable

In the short template of the notification, large information can’t be shown. Therefore we need  to make the notification expandable like this:

to make such an expandable notification we use the setStyle() method on the notification builder (nBuilder) object. In this expanded area we can display an image, any text, different messages, etc. In our Application, we have added an image by passing the instance of the  NotificationCompat.BigPictureStyle class to setStyle() method.

Kotlin

val imgBitmap = BitmapFactory.decodeResource(resources,R.drawable.gfg_green)
val nBuilder = NotificationCompat.Builder(this,CHANNEL_ID)
                    .setContentTitle(et1.text.toString())
                    .setContentText(et2.text.toString())
                    .setSmallIcon(R.drawable.spp_notification_foreground)
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                    .setLargeIcon(imgBitmap)
                    // Expandable notification
                    .setStyle(NotificationCompat.BigPictureStyle()
                            .bigPicture(imgBitmap)
                            // as we pass null in bigLargeIcon() so the large icon
                            // will goes away when the notification will be expanded.
                            .bigLargeIcon(null))
                    .build()

5. Making notification clickable

We need to make our notification clickable to perform some action by clicking the notification such as open an activity or system setting or any webpage etc. Now to perform such actions intent is needed (e.g. explicit or implicit intent). In our Application, we are making an Implicit intent to open the GFG official home page.

Kotlin

// Creating the Implicit Intent to
// open the home page of GFG
val intent1= Intent()
        intent1.action=Intent.ACTION_VIEW
        intent1.data=Uri.parse("https://www.geeksforgeeks.org/")

Now it is not necessary that whenever the notification will appear then the user will click it instantly, user can click it whenever he /she wants and therefore we also need to make an instance of PendingIntent which basically makes the intent action pending for future purpose.

Kotlin

val pendingIntent1=PendingIntent.getActivity(this, 5, intent1, PendingIntent.FLAG_UPDATE_CURRENT)

// Here the four parameters are context of activity,
// requestCode,Intent and flag of the pendingIntent respectively
// The request code is used to trigger a
// particular action in application activity
val nBuilder = NotificationCompat.Builder(this,CHANNEL_ID)
                    .setContentTitle(et1.text.toString())
                    .setContentText(et2.text.toString())
                    .setSmallIcon(R.drawable.notifications)
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                    .setLargeIcon(imgBitmap)
                    .setStyle(NotificationCompat.BigPictureStyle()
                            .bigPicture(imgBitmap)
                            .bigLargeIcon(null))
                    // here we are passing the pending intent
                    .setContentIntent(pendingIntent1)
                    // as we set auto cancel true, the notification
                    // will disappear after afret clicking it
                    .setAutoCancel(true)
                    .build()

6. Adding an action button to our notification

Sometimes there exists some action button at our notification template that is used to perform some action.

Here we also need an Intent and a PendingIntent. Then we need to pass the instance of the PendingIntent to addAction() method at the time of building the notification.

Kotlin

// Creating the Implicit Intent
// to open the GFG contribution page
val intent2 = Intent()
        intent2.action = Intent.ACTION_VIEW
        intent2.data = Uri.parse("https://www.geeksforgeeks.org/contribute/")

val nBuilder = NotificationCompat.Builder(this,CHANNEL_ID)
                    .setContentTitle(et1.text.toString())
                    .setContentText(et2.text.toString())
                    .setSmallIcon(R.drawable.notifications)
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                    .setLargeIcon(imgBitmap)
                    .setStyle(NotificationCompat.BigPictureStyle()
                            .bigPicture(imgBitmap)
                            .bigLargeIcon(null))
                    .setContentIntent(pendingIntent1)
                    .setAutoCancel(true)
                    // Here we need to pass 3 arguments which are
                    // icon id, title, pendingIntent respectively
                    // Here we pass 0 as icon id which means no icon
                    .addAction(0,"LET CONTRIBUTE",pendingIntent2)
                    .build()

Example

Let discuss all the concepts by making an Application named GFG_PushNotification. A sample GIF is given below to get an idea about what we are going to do in this article. Note that we are going to implement this project using the Kotlin language. 

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Kotlin as the programming language. Choose the API level according to your choice( Here we have chosen API Level 26).

After creating the project successfully, please paste some pictures into the drawable folder in the res directory. Now you can use the same pictures which I have used in my project otherwise you can choose pictures of your own choice. To download the same pictures please click on the below-given link:

CLICK HERE

***Please note that it is optional***

Step 2: Working with the activity_main.xml file

Go to the activity_main.xml file and refer to the following code. Below is the code for the activity_main.xml file.

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">

    <ImageView
        android:id="@+id/imgGFG"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="70dp"
        android:src="@drawable/gfg_white" />

    <!-- EditText for entering the title-->
    <EditText
        android:id="@+id/et1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/imgGFG"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp"
        android:background="#d7ffd9"
        android:hint="Enter The Title"
        android:padding="10dp"
        android:textSize="20sp"
        android:textStyle="bold" />

    <!-- EditText for entering the text-->
    <EditText
        android:id="@+id/et2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et1"
        android:layout_marginLeft="30dp"
        android:layout_marginTop="30dp"
        android:layout_marginRight="30dp"
        android:background="#d7ffd9"
        android:hint="Enter The Text"
        android:padding="10dp"
        android:textSize="20sp"
        android:textStyle="bold" />

    <!-- Button for sending notification-->
    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et2"
        android:layout_marginLeft="30dp"
        android:layout_marginTop="30dp"
        android:layout_marginRight="30dp"
        android:background="#0F9D58"
        android:text="send notification"
        android:textColor="#000000"
        android:textSize="20sp"
        android:textStyle="bold" />

</RelativeLayout>

Step 3: Insert a vector asset into the drawable folder in the res directory

Right-click on the drawable folder → New → Vector Asset → select appropriate Clip Art → give appropriate Name and adjust Size accordingly→ Next then click on the finish button as shown in the below image.

Step 4: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

import android.app.NotificationChannel
import android.app.NotificationManager
import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import android.graphics.BitmapFactory
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.NotificationCompat
import androidx.core.app.NotificationManagerCompat

class MainActivity : AppCompatActivity() {
    val CHANNEL_ID = "GFG"
    val CHANNEL_NAME = "GFG ContentWriting"
    val CHANNEL_DESCRIPTION = "GFG NOTIFICATION"

    // the String form of link for
    // opening the GFG home-page
    val link1 = "https://www.geeksforgeeks.org/"

    // the String form of link for opening
    // the GFG contribution-page
    val link2 = "https://www.geeksforgeeks.org/contribute/"
    lateinit var et1: EditText
    lateinit var et2: EditText
    lateinit var btn1: Button
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Binding Views by their IDs
        et1 = findViewById(R.id.et1)
        et2 = findViewById(R.id.et2)
        btn1 = findViewById(R.id.btn1)
        btn1.setOnClickListener {

            // Converting the .png Image file to a Bitmap!
            val imgBitmap = BitmapFactory.decodeResource(resources, R.drawable.gfg_green)

            // Making intent1 to open the GFG home page
            val intent1 = gfgOpenerIntent(link1)

            // Making intent2 to open The GFG contribution page
            val intent2 = gfgOpenerIntent(link2)

            // Making pendingIntent1 to open the GFG home
            // page after clicking the Notification
            val pendingIntent1 = PendingIntent.getActivity(this, 5, intent1, PendingIntent.FLAG_UPDATE_CURRENT)

            // Making pendingIntent2 to open the GFG contribution
            // page after clicking the actionButton of the notification
            val pendingIntent2 = PendingIntent.getActivity(this, 6, intent2, PendingIntent.FLAG_UPDATE_CURRENT)

            // By invoking the notificationChannel() function we
            // are registering our channel to the System
            notificationChannel()

            // Building the notification
            val nBuilder = NotificationCompat.Builder(this, CHANNEL_ID)

                    // adding notification Title
                    .setContentTitle(et1.text.toString())

                    // adding notification Text
                    .setContentText(et2.text.toString())

                    // adding notification SmallIcon
                    .setSmallIcon(R.drawable.ic_android_black_24dp)

                    // adding notification Priority
                    .setPriority(NotificationCompat.PRIORITY_DEFAULT)

                    // making the notification clickable
                    .setContentIntent(pendingIntent1)
                    .setAutoCancel(true)

                    // adding action button
                    .addAction(0, "LET CONTRIBUTE", pendingIntent2)

                    // adding largeIcon
                    .setLargeIcon(imgBitmap)

                    // making notification Expandable
                    .setStyle(NotificationCompat.BigPictureStyle()
                            .bigPicture(imgBitmap)
                            .bigLargeIcon(null))
                    .build()
            // finally notifying the notification
            val nManager = NotificationManagerCompat.from(this)
            nManager.notify(1, nBuilder)
        }
    }

    // Creating the notification channel
    private fun notificationChannel() {
        // check if the version is equal or greater
        // than android oreo version
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            // creating notification channel and setting
            // the description of the channel
            val channel = NotificationChannel(CHANNEL_ID, CHANNEL_NAME, NotificationManager.IMPORTANCE_DEFAULT).apply {
                description = CHANNEL_DESCRIPTION
            }
            // registering the channel to the System
            val notificationManager: NotificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
            notificationManager.createNotificationChannel(channel)
        }
    }

    // The function gfgOpenerIntent() returns
    // an Implicit Intent to open a webpage
    private fun gfgOpenerIntent(link: String): Intent {
        val intent = Intent()
        intent.action = Intent.ACTION_VIEW
        intent.data = Uri.parse(link)
        return intent
    }
}

Output: