android create notification
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(yourContext.getApplicationContext(), "notify_001");
Intent ii = new Intent(yourContext.getApplicationContext(), YourMainActivty.class);
PendingIntent pendingIntent = PendingIntent.getActivity(yourContext, 0, ii, 0);
NotificationCompat.BigTextStyle bigText = new NotificationCompat.BigTextStyle();
bigText.bigText(notificationsTextDetailMode); //detail mode is the "expanded" notification
bigText.setBigContentTitle(notificationTitleDetailMode);
bigText.setSummaryText(usuallyAppVersionOrNumberOfNotifications); //small text under notification
mBuilder.setContentIntent(pendingIntent);
mBuilder.setSmallIcon(R.mipmap.ic_launcher); //notification icon
mBuilder.setContentTitle(notificationTitle); //main title
mBuilder.setContentText(notificationText); //main text when you "haven't expanded" the notification yet
mBuilder.setPriority(Notification.PRIORITY_MAX);
mBuilder.setStyle(bigText);
NotificationManager mNotificationManager = (NotificationManager) yourContext.getSystemService(Context.NOTIFICATION_SERVICE);
NotificationChannel channel = new NotificationChannel("notify_001",
"Channel human readable title",
NotificationManager.IMPORTANCE_DEFAULT);
if (mNotificationManager != null) {
mNotificationManager.createNotificationChannel(channel);
}
if (mNotificationManager != null) {
mNotificationManager.notify(0, mBuilder.build());
}