您可以通过使用insistentFlag和androidAllowWhileIdle标志来持久保存声音（或在本例中为警报）。
以下示例使用Flutter本地通知v.12

static Future<void> showFullScreenNotification(
      Alarm alarm, tz.TZDateTime date) async {

    const int insistentFlag = 4;

    final Int64List vibrationPattern = Int64List(4);
    vibrationPattern[0] = 0;
    vibrationPattern[1] = 4000;
    vibrationPattern[2] = 4000;
    vibrationPattern[3] = 4000;

    AndroidNotificationDetails androidPlatformChannelSpecifics =
    AndroidNotificationDetails(
      alarm.id.toString(),
      'scheduled_alarm_channel',
      channelDescription: 'scheduled_alarm',
      priority: Priority.high,
      importance: Importance.high,
      additionalFlags: Int32List.fromList(<int>[insistentFlag]),
      playSound: true,
      audioAttributesUsage: AudioAttributesUsage.alarm,
      vibrationPattern: vibrationPattern,
    );

    NotificationDetails details =
    NotificationDetails(android: androidPlatformChannelSpecifics);

    await flutterLocalNotificationsPlugin.zonedSchedule(
      ...
      date,
      androidAllowWhileIdle: true,
      ...
    );
  }