Notification based Android interview questions and answers

1) What is the use of Notification Chanel and how to create it?

Notification Channels. Notification Channels allow us to separate notifications into different groups/categories. Basically, Notification Channel is designed for User. They can get full control of what they want to be notified about. If they don’t want any notification they can specifically turn off notifications for a certain channel. They can also specify importance as well as the preferred sound for a particular category of notifications and determine whether or not to override Do not disturb

The NotificationChannel constructor requires us to specify the channel_id and channel_name strings. The Importance argument is an int which specifies the level of interruption by the notification.

val  MessagesChannel = NotificationChannel(
                   MESSAGES_CHANNEL_ID,
                   context.getString(R.string_channel_name),
                   NotificationManager.IMPORTANCE_DEFAULT)
notificationManager.createNotificationChannel(privateMessagesChannel)

Here we have to create an application that schedules a task and send a notification. For that, we need to execute a particular job daily at a specific time defined by the user. We can do it using the AlarmManager in android. Android has a built-in AlarmManager class which makes scheduling tasks. AlarmManager provides access to system-level alarm services. This gives a way to perform any operations outside the lifetime of your application. So we can trigger events or actions even when your application is not running. Step to schedule  task is mentioned below:

  • We need a Broadcast Receiver to fire the alarm when our app is not running.
  • We also need to register this BroadcastReceiver in the Manifest file.
  • For Setting Alarm using Alarm Manager Class we will declare a PendingIntent and an AlarmManager variable In Activity.java. The PendingIntent will be used to set and cancel the alarms.
  • We used the setRepeating() method to set up a recurring alarm.

Please find below code for more detail:

// check task is scheduled or not
boolean alarmUp = (PendingIntent.getBroadcast(this, 0, 
        new Intent("com.example.dummy.AlarmReceiver"), 
        PendingIntent.FLAG_NO_CREATE) != null);
if (  !alarmUp) {
Intent intent = new Intent("com.example.dummy.AlarmReceiver");
intent.putExtra("activate", true);
PendingIntent pendingIntent =
                        PendingIntent.getBroadcast(this, 0, 
          intent, PendingIntent.FLAG_UPDATE_CURRENT);
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.set(Calendar.HOUR_OF_DAY, 0);   
calendar.set(Calendar.MINUTE, 1);
calendar.set(Calendar.SECOND, 0);
AlarmManager alarmManager =
                        (AlarmManager)
                        this.getSystemService(this.ALARM_SERVICE);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,
                        calendar.getTimeInMillis(), AlarmManager.INTERVAL_DAY,
                        pendingIntent);
calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.set(Calendar.HOUR_OF_DAY, 7);   
calendar.set(Calendar.MINUTE, 0);
alarmManager = (AlarmManager)
                        this.getSystemService(this.ALARM_SERVICE);
PendingIntent pendingIntent2 =
                        PendingIntent.getBroadcast(this, 1, 
                    intent, PendingIntent.FLAG_UPDATE_CURRENT);
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP,
                        calendar.getTimeInMillis(),
                        AlarmManager.INTERVAL_DAY, pendingIntent2);

What is NotificationManager class?

A) The NotificationManager class is used to display notifications on the device’s status bar

 To display a notification on upper left of Android screen, which of the following class you need to use?

A) NotificationManager + Notification

You need to process when user clicks on a notification on upper left of Android screen?

A) PendingIntent

Which is the method you need to use to post a notification to be shown in the status bar?

A) notify(…)

A

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