title: Notification Not open Activity onCLick
body: <p>I want to create a notification which should open activity when click on it. But when I click on notification activity not open . 
  Here is my code:</p>
  
  <pre><code>NotificationManager notificationManager = (NotificationManager) context
              .getSystemService(Context.NOTIFICATION_SERVICE);
  
      Intent intent = new Intent(context, MessageReceivedActivity.class);
      intent.putExtra("payload", payload);
      intent.setAction(Long.toString(System.currentTimeMillis()));
      intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
      PendingIntent pendingIntent = PendingIntent.getActivity(context, 0,
              intent, PendingIntent.FLAG_CANCEL_CURRENT);
  
      Notification.Builder notification = new Notification.Builder(context)
  
      .setContentTitle("Message Received")
      .setSmallIcon(R.drawable.icon)
      .setContentText(payload)
      .setContentIntent(pendingIntent)
      .setAutoCancel(true);
  
      Notification notificationn = notification.getNotification();
  
      notificationManager.notify(0, notificationn);
  </code></pre>