Bottom Navigation Bar Issues

[akyjoe]

We were able to use Bottom navigation bar, by adding parent view "HomeView" in which we are calling all the child views. Views are working just fine.

Now the issue is about the DataService is been called each time, on swap of views. Below is our code for locator.dart

locator.registerLazySingleton(() => DialogService());
locator.registerLazySingleton(() => NavigationService());
locator.registerLazySingleton(() => AuthenticationService());
locator.registerLazySingleton(() => DataService()); 

locator.registerSingleton<ViewModel1>(ViewModel1());
locator.registerSingleton<ViewModel2>(ViewModel2());
locator.registerSingleton<ViewModel3>(ViewModel3());

In the view we have added initialiseSpecialViewModelsOnce: true viewModelBuilder: () => locator<ViewModel1>() as well.

When we execute:

flutter: Error while creating DataService
flutter: Stack trace:
 #0      defaultBinaryMessenger.<anonymous closure> (package:flutter/src/services/binary_messenger.dart:76:7)
#1      defaultBinaryMessenger (package:flutter/src/services/binary_messenger.dart:89:4)
#2      MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:140:62)
#3      MethodChannel.setMethodCallHandler (package:flutter/src/services/platform_channel.dart:375:5)
#4      new MethodChannelFirestore (package:cloud_firestore_platform_interface/src/method_channel/method_channel_firestore.dart:27:13)
#5      FirestorePlatform.instance (package:cloud_firestore_platform_interface/cloud_firestore_platform_interface.dart:63:19)
#6      new Firestore (package:cloud_firestore/src/firestore.dart:26:42)
#7      Firestore.instance (package:cloud_firestore/src/firestore.dart:29:36)
#8      new DataService (package:Vaccine/app/service/data.dart:14:67)
#9      setupLocator.<anonymous closure> (package:Vaccine/app/locator.dart:21:39)
#10     _ServiceFactory.getObject (package:get_it/get_it_impl.dart:128:40)
#11     _GetItImplementation.get (package:get_it/get_it_impl.dart:276:34)
#12     _GetItImplementation.call (package:get_it/get_it_impl.dart:288:12)
#13     new AuthenticationService (package:Vaccine/app/service/auth.dart:10:43)
#14     setupLocator.<anonymous closure> (package:Vaccine/app/locator.dart:19:39)
#15     _ServiceFactory.getObject (package:get_it/get_it_impl.dart:128:40)
#16     _GetItImplementation.get (package:get_it/get_it_impl.dart:276:34)
#17     _GetItImplementation.call (package:get_it/get_it_impl.dart:288:12)
#18     new ScheduleScreenModel (package:Vaccine/app/screenmodels/view_model_1.dart:14:63)
#19     setupLocator (package:Vaccine/app/locator.dart:24:50)
#20     main (package:Vaccine/main.dart:9:3)
#21     _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:241:25)
#22     _rootRun (dart:async/zone.dart:1184:13)
#23     _CustomZone.run (dart:async/zone.dart:1077:19)
#24     _runZoned (dart:async/zone.dart:1619:10)
#25     runZonedGuarded (dart:async/zone.dart:1608:12)
#26     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:233:5)
#27     _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:301:19)
#28     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)
flutter: Error while creating AuthenticationService
flutter: Stack trace:
 #0      defaultBinaryMessenger.<anonymous closure> (package:flutter/src/services/binary_messenger.dart:76:7)
#1      defaultBinaryMessenger (package:flutter/src/services/binary_messenger.dart:89:4)
#2      MethodChannel.binaryMessenger (package:flutter/src/services/platform_channel.dart:140:62)
#3      MethodChannel.setMethodCallHandler (package:flutter/src/services/platform_channel.dart:375:5)
#4      new MethodChannelFirestore (package:cloud_firestore_platform_interface/src/method_channel/method_channel_firestore.dart:27:13)
#5      FirestorePlatform.instance (package:cloud_firestore_platform_interface/cloud_firestore_platform_interface.dart:63:19)
#6      new Firestore (package:cloud_firestore/src/firestore.dart:26:42)
#7      Firestore.instance (package:cloud_firestore/src/firestore.dart:29:36)
#8      new DataService (package:Vaccine/app/service/data.dart:14:67)
#9      setupLocator.<anonymous closure> (package:Vaccine/app/locator.dart:21:39)
#10     _ServiceFactory.getObject (package:get_it/get_it_impl.dart:128:40)
#11     _GetItImplementation.get (package:get_it/get_it_impl.dart:276:34)
#12     _GetItImplementation.call (package:get_it/get_it_impl.dart:288:12)
#13     new AuthenticationService (package:Vaccine/app/service/auth.dart:10:43)
#14     setupLocator.<anonymous closure> (package:Vaccine/app/locator.dart:19:39)
#15     _ServiceFactory.getObject (package:get_it/get_it_impl.dart:128:40)
#16     _GetItImplementation.get (package:get_it/get_it_impl.dart:276:34)
#17     _GetItImplementation.call (package:get_it/get_it_impl.dart:288:12)
#18     new ScheduleScreenModel (package:Vaccine/app/screenmodels/view_model_1.dart:14:63)
#19     setupLocator (package:Vaccine/app/locator.dart:24:50)
#20     main (package:Vaccine/main.dart:9:3)
#21     _runMainZoned.<anonymous closure>.<anonymous closure> (dart:ui/hooks.dart:241:25)
#22     _rootRun (dart:async/zone.dart:1184:13)
#23     _CustomZone.run (dart:async/zone.dart:1077:19)
#24     _runZoned (dart:async/zone.dart:1619:10)
#25     runZonedGuarded (dart:async/zone.dart:1608:12)
#26     _runMainZoned.<anonymous closure> (dart:ui/hooks.dart:233:5)
#27     _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:301:19)
#28     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)

Code for view_mode_1.dart 14:63 is:

final AuthenticationService _authenticationService = locator<AuthenticationService>();
final DataService _dataService = locator<DataService>();

Kindly suggest how to rectify this?

Originally posted by @akyjoe in https://github.com/FilledStacks/flutter-tutorials/issues/86#issuecomment-669177084

Other issue is, how can we switch BottomNavigationBar tabs programmatically or by tapping any button in current view?