Android Notifications

Android Toast class provides a handy way to show users alerts but problem is that these alerts are not persistent which means alert flashes on the screen for a few seconds and then disappears.
For important messages to be given to the user, it is required to have more persistent method. A notification is a message you can display as an icon at the top of the device which we call notification bar or status bar.
Android Notification Bar To see the details of the notification, you will have to select the icon which will display notification drawer having detail about the notification. While working with emulator with virtual device, you will have to click and drag down the status bar to expand it which will give you detail as follows. This will be just 64 dp tall and called normal view.
Android Notification Detail Above expanded form can have a Big View which will have additional detail about the notification. You can add upto six additional lines in the notifciation. The following screenshot shows such notification.
Android Notification Big View

Create and Send Notifications

You have simple way to create a notification. Follow the following steps in your application to create a notification:

Step 1 - Create Notification Builder

As a first step is to create a notification builder using NotificationCompat.Builder.build(). You will use Notification Builder to set various Notification properties like its small and large icons, title, priority etc.
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)

Step 2 - Setting Notification Properties

Once you have Builder object, you can set its Notification properties using Builder object as per your requirement. But this is mandatory to set at least following:
  • A small icon, set by setSmallIcon()
  • A title, set by setContentTitle()
  • Detail text, set by setContentText()
mBuilder.setSmallIcon(R.drawable.notification_icon);
mBuilder.setContentTitle("Notification Alert, Click Me!");
mBuilder.setContentText("Hi, This is Android Notification Detail!");
You have plenty of optional properties which you can set for your notification. To learn more about them, see the reference documentation for NotificationCompat.Builder.

Step 3 - Attach Actions

This is an optional part and required if you want to attach an action with the notification. An action allows users to go directly from the notification to an Activity in your application, where they can look at one or more events or do further work.
The action is defined by a PendingIntent containing an Intent that starts an Activity in your application. To associate the PendingIntent with a gesture, call the appropriate method of NotificationCompat.Builder. For example, if you want to start Activity when the user clicks the notification text in the notification drawer, you add the PendingIntent by calling setContentIntent().
A PendingIntent object helps you to perform an action on your application’s behalf, often at a later time, without caring of whether or not your application is running.
We take help of stack builder object which will contain an artificial back stack for the started Activity. This ensures that navigating backward from the Activity leads out of your application to the Home screen.
Intent resultIntent = new Intent(this, ResultActivity.class);
TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
stackBuilder.addParentStack(ResultActivity.class);

// Adds the Intent that starts the Activity to the top of the stack
stackBuilder.addNextIntent(resultIntent);
PendingIntent resultPendingIntent =
        stackBuilder.getPendingIntent(
            0,
            PendingIntent.FLAG_UPDATE_CURRENT
        );
mBuilder.setContentIntent(resultPendingIntent);

Step 4 - Issue the notification

Finally, you pass the Notification object to the system by calling NotificationManager.notify() to send your notification. Make sure you call NotificationCompat.Builder.build() method on builder object before notifying it. This method combines all of the options that have been set and return a new Notification object.
NotificationManager mNotificationManager =
    (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    
// notificationID allows you to update the notification later on.
mNotificationManager.notify(notificationID, mBuilder.build());

The NotificationCompat.Builder Class

The NotificationCompat.Builder class allows easier control over all the flags, as well as help constructing the typical notification layouts. Following are few important and most frequently used methods available as a part of NotificationCompat.Builder class.
S.N.Constants & Description
1Notification build()
Combine all of the options that have been set and return a new Notification object.
2 NotificationCompat.Builder setAutoCancel (boolean autoCancel)
Setting this flag will make it so the notification is automatically canceled when the user clicks it in the panel.
3NotificationCompat.Builder setContent (RemoteViews views)
Supply a custom RemoteViews to use instead of the standard one.
4NotificationCompat.Builder setContentInfo (CharSequence info)
Set the large text at the right-hand side of the notification.
5NotificationCompat.Builder setContentIntent (PendingIntent intent)
Supply a PendingIntent to send when the notification is clicked.
6NotificationCompat.Builder setContentText (CharSequence text)
Set the text (second row) of the notification, in a standard notification.
7 NotificationCompat.Builder setContentTitle (CharSequence title)
Set the text (first row) of the notification, in a standard notification.
8NotificationCompat.Builder setDefaults (int defaults)
Set the default notification options that will be used.
9 NotificationCompat.Builder setLargeIcon (Bitmap icon)
Set the large icon that is shown in the ticker and notification.
10NotificationCompat.Builder setNumber (int number)
Set the large number at the right-hand side of the notification.
11 NotificationCompat.Builder setOngoing (boolean ongoing)
Set whether this is an ongoing notification.
12NotificationCompat.Builder setSmallIcon (int icon)
Set the small icon to use in the notification layouts.
13 NotificationCompat.Builder setStyle (NotificationCompat.Style style)
Add a rich notification style to be applied at build time.
14 NotificationCompat.Builder setTicker (CharSequence tickerText)
Set the text that is displayed in the status bar when the notification first arrives.
15NotificationCompat.Builder setVibrate (long[] pattern)
Set the vibration pattern to use.
16NotificationCompat.Builder setWhen (long when)
Set the time that the event occurred. Notifications in the panel are sorted by this time.

Example

Following example shows the functionality of a Android notification using a NotificationCompat.Builder Class which has been introduced in Android 4.1.
StepDescription
1You will use Eclipse IDE to create an Android application and name it as NotificationDemo under a package com.example.notificationdemo. While creating this project, make sure you Target SDK and Compile With at the latest version of Android SDK to use higher levels of APIs.
2Modify src/MainActivity.java file and add the code to define three methods startNotification(), cancelNotification() and updateNotification() to cover maximum functionality related to Android notifications.
3Create a new Java file src/NotificationView.java, which will be used to display new layout as a part of new activity which will be started when user will click any of the notifications
4Copy image woman.png in res/drawable-* folders and this image will be used as Notification icons. You can use images with different resolution in case you want to provide them for different devices.
5Modify layout XML file res/layout/activity_main.xml to add three buttons in linear layout.
6Create a new layout XML file res/layout/notification.xml. This will be used as layout file for new activity which will start when user will click any of the notifications.
7Modify res/values/strings.xml to define required constant values
8Run the application to launch Android emulator and verify the result of the changes done in the aplication.
Following is the content of the modified main activity file src/com.example.notificationdemo/MainActivity.java. This file can include each of the fundamental lifecycle methods.
package com.example.notificationdemo;

import android.os.Bundle;
import android.app.Activity;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.TaskStackBuilder;
import android.content.Context;
import android.content.Intent;
import android.support.v4.app.NotificationCompat;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {
   private NotificationManager mNotificationManager;
   private int notificationID = 100;
   private int numMessages = 0;

   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      Button startBtn = (Button) findViewById(R.id.start);
      startBtn.setOnClickListener(new View.OnClickListener() {
         public void onClick(View view) {
            displayNotification();
         }
      });

      Button cancelBtn = (Button) findViewById(R.id.cancel);
      cancelBtn.setOnClickListener(new View.OnClickListener() {
         public void onClick(View view) {
            cancelNotification();
         }
      });
   
      Button updateBtn = (Button) findViewById(R.id.update);
      updateBtn.setOnClickListener(new View.OnClickListener() {
         public void onClick(View view) {
            updateNotification();
         }
      });
   }
   protected void displayNotification() {
      Log.i("Start", "notification");

      /* Invoking the default notification service */
      NotificationCompat.Builder  mBuilder = 
      new NotificationCompat.Builder(this); 

      mBuilder.setContentTitle("New Message");
      mBuilder.setContentText("You've received new message.");
      mBuilder.setTicker("New Message Alert!");
      mBuilder.setSmallIcon(R.drawable.woman);

      /* Increase notification number every time a new notification arrives */
      mBuilder.setNumber(++numMessages);
      
      /* Creates an explicit intent for an Activity in your app */
      Intent resultIntent = new Intent(this, NotificationView.class);

      TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
      stackBuilder.addParentStack(NotificationView.class);

      /* Adds the Intent that starts the Activity to the top of the stack */
      stackBuilder.addNextIntent(resultIntent);
      PendingIntent resultPendingIntent =
         stackBuilder.getPendingIntent(
            0,
            PendingIntent.FLAG_UPDATE_CURRENT
         );

      mBuilder.setContentIntent(resultPendingIntent);

      mNotificationManager =
      (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

      /* notificationID allows you to update the notification later on. */
      mNotificationManager.notify(notificationID, mBuilder.build());
   }

   protected void cancelNotification() {
      Log.i("Cancel", "notification");
      mNotificationManager.cancel(notificationID);
   }

   protected void updateNotification() {
      Log.i("Update", "notification");

      /* Invoking the default notification service */
      NotificationCompat.Builder  mBuilder = 
      new NotificationCompat.Builder(this); 

      mBuilder.setContentTitle("Updated Message");
      mBuilder.setContentText("You've got updated message.");
      mBuilder.setTicker("Updated Message Alert!");
      mBuilder.setSmallIcon(R.drawable.woman);

     /* Increase notification number every time a new notification arrives */
      mBuilder.setNumber(++numMessages);
      
      /* Creates an explicit intent for an Activity in your app */
      Intent resultIntent = new Intent(this, NotificationView.class);

      TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
      stackBuilder.addParentStack(NotificationView.class);

      /* Adds the Intent that starts the Activity to the top of the stack */
      stackBuilder.addNextIntent(resultIntent);
      PendingIntent resultPendingIntent =
         stackBuilder.getPendingIntent(
            0,
            PendingIntent.FLAG_UPDATE_CURRENT
         );

      mBuilder.setContentIntent(resultPendingIntent);

      mNotificationManager =
      (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

      /* Update the existing notification using same notification ID */
      mNotificationManager.notify(notificationID, mBuilder.build());
   }
}
Following is the content of the modified main activity file src/com.example.notificationdemo/NotificationView.java.
package com.example.notificationdemo;

import android.os.Bundle;
import android.app.Activity;

public class NotificationView extends Activity{
   @Override
   public void onCreate(Bundle savedInstanceState)
   {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.notification);
   }

}
Following will be the content of res/layout/activity_main.xml file:
 xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   android:orientation="vertical" >
Following will be the content of res/layout/notification.xml file:
xml version="1.0" encoding="utf-8"?>
 xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"    >
   
   android:layout_width="fill_parent"
   android:layout_height="400dp"
   android:text="Hi, Your Detailed notification view goes here...." />
Following will be the content of res/values/strings.xml to define two new constants:
xml version="1.0" encoding="utf-8"?>


     name="app_name">NotificationDemo
     name="action_settings">Settings
     name="hello_world">Hello world!
     name="start_note">Start Notification
     name="cancel_note">Cancel Notification
     name="update_note">Update Notification
Following is the default content of AndroidManifest.xml:
xml version="1.0" encoding="utf-8"?>
 xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.notificationdemo"
    android:versionCode="1"
    android:versionName="1.0" >

    
        android:minSdkVersion="17"
        android:targetSdkVersion="17" />

    
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        
            android:name="com.example.notificationdemo.MainActivity"
            android:label="@string/app_name" >
            
                 android:name="android.intent.action.MAIN" />

                 android:name="android.intent.category.LAUNCHER" />
android:name=".NotificationView" android:label="Details of notification" android:parentActivityName=".MainActivity"> android:name="android.support.PARENT_ACTIVITY" android:value=".MainActivity"/> Let's try to run your NotificationDemo application. I assume you had created your AVD while doing environment setup. To run the app from Eclipse, open one of your project's activity files and click Run Eclipse Run Icon icon from the toolbar. Eclipse installs the app on your AVD and starts it and if everything is fine with your setup and application, it will display following Emulator window:
Android Notification Start Now click Start Notification button, you will see at the top a message "New Message Alert!" will display momentarily and after that you will have following screen having a small icon at the top left corner.
Android Notification Start Icon Now lets expand the view, long click on the small icon, after a second it will display date information and this is the time when you should drag status bar down without releasing mouse. You will see status bar will expand and you will get following screen:
Android Notification Expanded Now let's try to click on the image icon, this will launch your new activity which you have set using intent and you will have following screen:
Android Notification New Activity Next, you can click on "Detail of notification" and it will take you back to the main screen where you can try using Update Notification button which will update existing notification and number will increase by 1 but if you will send notification with new notification ID then it will keep adding in the stack and you see them separately listed on the screen.

Big View Notification

The following code snippet demonstrates how to alter the notification created in the previous snippet to use the Inbox big view style. I'm going to update displayNotification() modification method to show this functionality:
   protected void displayNotification() {
      Log.i("Start", "notification");

      /* Invoking the default notification service */
      NotificationCompat.Builder  mBuilder = 
      new NotificationCompat.Builder(this); 

      mBuilder.setContentTitle("New Message");
      mBuilder.setContentText("You've received new message.");
      mBuilder.setTicker("New Message Alert!");
      mBuilder.setSmallIcon(R.drawable.woman);

      /* Increase notification number every time a new notification arrives */
      mBuilder.setNumber(++numMessages);


      /* Add Big View Specific Configuration */
      NotificationCompat.InboxStyle inboxStyle =
             new NotificationCompat.InboxStyle();

      String[] events = new String[6];
      events[0] = new String("This is first line....");
      events[1] = new String("This is second line...");
      events[2] = new String("This is third line...");
      events[3] = new String("This is 4th line...");
      events[4] = new String("This is 5th line...");
      events[5] = new String("This is 6th line...");

      // Sets a title for the Inbox style big view
      inboxStyle.setBigContentTitle("Big Title Details:");
      // Moves events into the big view
      for (int i=0; i < events.length; i++) {

         inboxStyle.addLine(events[i]);
      }
      mBuilder.setStyle(inboxStyle);
       
      
      /* Creates an explicit intent for an Activity in your app */
      Intent resultIntent = new Intent(this, NotificationView.class);

      TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
      stackBuilder.addParentStack(NotificationView.class);

      /* Adds the Intent that starts the Activity to the top of the stack */
      stackBuilder.addNextIntent(resultIntent);
      PendingIntent resultPendingIntent =
         stackBuilder.getPendingIntent(
            0,
            PendingIntent.FLAG_UPDATE_CURRENT
         );

      mBuilder.setContentIntent(resultPendingIntent);

      mNotificationManager =
      (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

      /* notificationID allows you to update the notification later on. */
      mNotificationManager.notify(notificationID, mBuilder.build());
   }
Now if you will try to run your application then you will find following result in expanded form of the view:
Android Notification Big View

 
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