Flutter show local notifications at exact time using workmanager - flutter

Question

I want to set the local notification in flutter (android app), I got to know about workmanager package but I don't know how to use it for my purpose. I want to send notifications at the exact time which is selected by the user.
Time Selection:
Container(
padding: EdgeInsets.all(15),
child: IconButton(icon: Icon(Icons.alarm, color: Colors.white, size: 70,),
onPressed: (){
DatePicker.showTimePicker(context,
theme: DatePickerTheme(
containerHeight: 210.0,
),
showTitleActions: true, onConfirm: (time) {
ttime = '${time.hour} : ${time.minute} : ${time.second}';
//print(_time);
_setNotifyTime();
setState(() {});
}, currentTime: DateTime.now(), locale: LocaleType.en);
setState(() {});
}),
),
Saving this time in sharedpreferences:
Future<void> _setNotifyTime() async{
final prefs = await SharedPreferences.getInstance();
final savedNotifyTime = await _getStringFromSharedPrefs();
await prefs.setString('notificationTime', ttime);
//print("this $savedNotifyTime");
return savedNotifyTime;
}
Getting this time from shared preferences:
Future<String> _getStringFromSharedPrefs() async{
final prefs = await SharedPreferences.getInstance();
notifyTime = prefs.getString('notificationTime');
return notifyTime;
}
Flutter local notification as per selected time:
Future<void> showDailyAtTime() async {
var splited = notifyTime.split(':');
int hour = int.parse(splited[0]);
int minute = int.parse(splited[1]);
int second = int.parse(splited[2]);
print(hour.toString());
print(minute.toString());
print(second.toString());
var reviewTime = Time(hour, minute, second);
var androidChannelSpecifics = AndroidNotificationDetails(
'CHANNEL_ID 2',
'CHANNEL_NAME 2',
"CHANNEL_DESCRIPTION 2",
importance: Importance.max,
priority: Priority.high,
);
var iosChannelSpecifics = IOSNotificationDetails();
var platformChannelSpecifics =
NotificationDetails(android: androidChannelSpecifics, iOS: iosChannelSpecifics);
await flutterLocalNotificationsPlugin.showDailyAtTime(
0,
'Title at ${reviewTime.hour}:${reviewTime.minute}.${reviewTime.second}',
'Test Body', //null
reviewTime,
platformChannelSpecifics,
payload: 'Test Payload',
);
}
Workmanager implementation:
void callbackDispatcher() {
Workmanager().executeTask((taskName, inputData) async {
notificationPlugin.showDailyAtTime();
return Future.value(true);
});
}
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Workmanager().initialize(callbackDispatcher);
await Workmanager().registerPeriodicTask("test_workertask", "test_workertask",
inputData: {"data1": "value1", "data2": "value2"},
frequency: Duration(minutes: 15),
initialDelay: Duration(minutes: 15));
runApp(MyApp());
}
This is working when I am calling it from a button in-app but as soon as I go in the background it doesn't work.
It is giving the following error, when I implement the above code:
HostComposition ext ANDROID_EMU_CHECKSUM_HELPER_v1 ANDROID_EMU_dma_v1 ANDROID_EMU_direct_mem ANDROID_EMU_host_composition_v1 ANDROID_EMU_host_composition_v2 ANDROID_EMU_vulkan ANDROID_EMU_deferred_vulkan_commands ANDROID_EMU_vulkan_null_optional_strings ANDROID_EMU_vulkan_create_resources_with_requirements ANDROID_EMU_YUV_Cache ANDROID_EMU_async_unmap_buffer ANDROID_EMU_vulkan_ignored_handles ANDROID_EMU_vulkan_free_memory_sync ANDROID_EMU_vulkan_shader_float16_int8 ANDROID_EMU_vulkan_async_queue_submit GL_OES_vertex_array_object GL_KHR_texture_compression_astc_ldr ANDROID_EMU_host_side_tracing ANDROID_EMU_async_frame_commands ANDROID_EMU_gles_max_version_2
D/EGL_emulation( 6089): eglMakeCurrent: 0xe90561a0: ver 2 0 (tinfo 0xe0eadb70)
E/flutter ( 6089): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: NoSuchMethodError: The method 'split' was called on null.
E/flutter ( 6089): Receiver: null
E/flutter ( 6089): Tried calling: split(":")
E/flutter ( 6089): #0 Object.noSuchMethod (dart:core- patch/object_patch.dart:54:5)
E/flutter ( 6089): #1 NotificationPlugin.showDailyAtTime (package:finance_manager/widgets/NotificationPlugin.dart:107:30)
E/flutter ( 6089): #2 callbackDispatcher.<anonymous closure> (package:finance_manager/main.dart:14:24)
E/flutter ( 6089): #3 callbackDispatcher.<anonymous closure> (package:finance_manager/main.dart:12:29)
E/flutter ( 6089): #4 Workmanager.executeTask.<anonymous closure> (package:workmanager/src/workmanager.dart:89:28)
E/flutter ( 6089): #5 Workmanager.executeTask.<anonymous closure> (package:workmanager/src/workmanager.dart:87:45)
E/flutter ( 6089): #6 MethodChannel._handleAsMethodCall (package:flutter/src/services/platform_channel.dart:435:55)
E/flutter ( 6089): #7 MethodChannel.setMethodCallHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:382:34)
E/flutter ( 6089): #8 _DefaultBinaryMessenger.handlePlatformMessage (package:flutter/src/services/binding.dart:284:33)
E/flutter ( 6089): #9 _invoke3.<anonymous closure> (dart:ui/hooks.dart:221:15)
E/flutter ( 6089): #10 _rootRun (dart:async/zone.dart:1354:13)
E/flutter ( 6089): #11 _CustomZone.run (dart:async/zone.dart:1258:19)
E/flutter ( 6089): #12 _CustomZone.runGuarded (dart:async/zone.dart:1162:7)
E/flutter ( 6089): #13 _invoke3 (dart:ui/hooks.dart:220:10)
E/flutter ( 6089): #14 PlatformDispatcher._dispatchPlatformMessage (dart:ui/platform_dispatcher.dart:457:7)
E/flutter ( 6089): #15 _dispatchPlatformMessage (dart:ui/hooks.dart:90:31)
E/flutter ( 6089):
I/WM-WorkerWrapper( 6089): Worker result SUCCESS for Work [ id=87272c98-d905-4b69-a1ce-86c13336ab8b, tags={ be.tramckrijte.workmanager.BackgroundWorker } ]
Please help me.
Thanks for your replies in advance.