why android 8.0 oreo version not trigger the notification - android-studio

Question

I Made the Notification part in my developing mobile application. It's working perfectly in kitkat down versions as well as upper versions but oreo version. Oreo version it's not trigger the notification. what is the reason.. Following are my codes..
Alert Activity
List<Time> times = new ArrayList<>();
times.add(new Time(hour, mminute));
Intent intent = new Intent(this, MyBroadcastReceiver.class);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
for (Time time : times) {
PendingIntent pendingIntent = PendingIntent.getBroadcast(this.getApplicationContext(), broadcastCodeCus++, intent, 0);
Calendar cal_alarm = Calendar.getInstance();
cal_alarm.set(Calendar.HOUR_OF_DAY, Integer.valueOf(hour));
cal_alarm.set(Calendar.MINUTE, Integer.valueOf(mminute));
cal_alarm.set(Calendar.SECOND, 00);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
alarmManager.setExact(AlarmManager.RTC_WAKEUP, cal_alarm.getTimeInMillis(), pendingIntent);
Toast.makeText(this, "Alarm > KITKAT & Alarm Set For: " + hour + " : " + mminute, Toast.LENGTH_SHORT).show();
}
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
alarmManager.set(AlarmManager.RTC_WAKEUP, cal_alarm.getTimeInMillis(), pendingIntent);
Toast.makeText(this, "Alarm < KITKAT & Alarm Set For: " + hour + " : " + mminute, Toast.LENGTH_SHORT).show();
}
customText.append(broadcastCodeCus + ". " + time.hour + ":" + time.minute + "\n");
}
MyBroadcastReceiver
NotificationManager notificationManager=(NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
Intent repeating_intent= new Intent(context,secondActivity.class);
repeating_intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendingIntent= PendingIntent.getActivity(context,100,repeating_intent,PendingIntent.FLAG_UPDATE_CURRENT);
NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(context,CHANNEL_ID)
.setContentIntent(pendingIntent)
.setSmallIcon(R.drawable.drink)
.setContentTitle(textTitle)
.setContentText(textContent)
.setStyle(new NotificationCompat.BigTextStyle()
.bigText(textContent))
.setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_ALARM))
.setAutoCancel(true)
.setPriority(NotificationCompat.PRIORITY_HIGH) // >=API level 21
.setLights(Color.WHITE, 2000, 3000)
.setVisibility(NotificationCompat.VISIBILITY_PUBLIC); // >=API level 21
notificationManager.notify(100,mBuilder.build());
}

Answer 1

In Android Oreo, it's a must to use a channel with your Notification Builder
you can follow the following code for the Notification Channel..
// Sets an ID for the notification, so it can be updated.
int notifyID = 1;
String CHANNEL_ID = "my_channel_01";// The id of the channel.
CharSequence name = getString(R.string.channel_name);// The user-visible name of the channel.
int importance = NotificationManager.IMPORTANCE_HIGH;
NotificationChannel mChannel = new NotificationChannel(CHANNEL_ID, name, importance);
// Create a notification and set the notification channel.
Notification notification = new Notification.Builder(MainActivity.this)
.setContentTitle("New Message")
.setContentText("You've received new messages.")
.setSmallIcon(R.drawable.ic_notify_status)
.setChannelId(CHANNEL_ID)
.build();