FlutterNativeView does not receive incoming BinaryMessages when running in CoroutineWorker

[nrkramer]

Steps to Reproduce

1. Write boilerplate code to run a CoroutineWorker from WorkManager
2. Write boilerplate code to run a callback routine in Flutter from kotlin. This callback opens a MethodChannel and sends 'initialized' to kotlin.
3. Write boilerplate code to run isolate in CoroutineWorker, wait for initialized message in kotlin from flutter, then call whatever function you want in flutter from kotlin (through the same MethodChannel)
4. Write boilerplate code to have flutter start this worker on a button press
5. PRESS THE BUTTON!!!!

Here's my worker and flutter callback: https://gist.github.com/nrkramer/71f202302a177a454244c09188334b2b

Logs

[        ] Updating files
[ +644 ms] DevFS: Sync finished
[   +1 ms] Syncing files to device Android SDK built for x86... (completed in 2,555ms, longer than expected)
[        ] Synced 12.7MB.
[   +1 ms] Sending to VM service: _flutter.listViews({})
[   +3 ms] Result: {type: FlutterViewList, views: [{type: FlutterView, id: _flutterView/0xde4e270c, isolate: {type: @Isolate, fixedId: true, id: isolates/474932352, name: main.dart$main-474932352, number: 474932352}}]}
[        ] <- accept
[        ] Connected to _flutterView/0xde4e270c.
[   +2 ms] �  To hot reload changes while running, press "r". To hot restart (and rebuild state), press "R".
[   +1 ms] An Observatory debugger and profiler on Android SDK built for x86 is available at: http://127.0.0.1:55664/
[        ] For a more detailed help message, press "h". To detach, press "d"; to quit, press "q".
[+22655 ms] D/MainActivity( 9500): Notify run check requested
[  +23 ms] D/MainActivity( 9500): Notify is running: false
[+2755 ms] D/MainActivity( 9500): Immediate update requested
[ +294 ms] D/ShowtapNotifyJob( 9500): SetMethodCallHandler was set
[ +276 ms] I/flutter ( 9500): Callback dispatcher called
[  +16 ms] I/flutter ( 9500): Called initialized
[+4715 ms] D/ShowtapNotifyJob( 9500): Calling invokeMethod
[   +7 ms] I/flutter ( 9500): Method was called
[  +15 ms] I/WM-WorkerWrapper( 9500): Worker result SUCCESS for Work [ id=2ad8aaf4-5eb2-4abe-9d4e-8dfad326a428, tags={ apps.blanket.showtap.NotificationWorker } ]
[+36873 ms] D/EGL_emulation( 9500): eglMakeCurrent: 0xdff05960: ver 3 1 (tinfo 0xdff03850)
[+1810 ms] Service protocol connection closed.
[   +1 ms] Lost connection to device.
[   +3 ms] DevFS: Deleting filesystem on the device (file:///data/user/0/apps.blanket.showtap/code_cache/showtapEXYPXM/showtap/)
[   +1 ms] Sending to VM service: _deleteDevFS({fsName: showtap})
[ +256 ms] Ignored error while cleaning up DevFS: TimeoutException after 0:00:00.250000: Future not completed
[   +5 ms] "flutter run" took 93,638ms.
[        ] "flutter run" took 93,638ms.

   info - The value of the field '_imagesBaseURL' isn't used - lib\database\TMDbDatabase.dart:15:10 - unused_field
   info - Await only futures - lib\main.dart:14:3 - await_only_futures
   info - Unused import: 'package:showtap/custom_routes.dart' - lib\ui\pages\discover_page.dart:3:8 - unused_import
   info - Unused import: 'package:showtap/ui/pages/movie_details_page.dart' - lib\ui\pages\discover_page.dart:4:8 - unused_import
   info - Unused import: 'package:showtap/ui/widgets/movie_smallitem.dart' - lib\ui\pages\discover_page.dart:5:8 - unused_import
   info - Unused import: 'package:showtap/metadata/movie_metadata.dart' - lib\ui\pages\discover_page.dart:7:8 - unused_import
   info - Unused import: 'package:showtap/metadata/local_movie_db.dart' - lib\ui\pages\discover_page.dart:8:8 - unused_import

    • Flutter version 1.4.19-pre.3 at D:\Development\flutter
    • Framework revision 404f66d968 (2 hours ago), 2019-04-12 03:01:18 -0400
    • Engine revision f804c293f3
    • Dart version 2.2.1 (build 2.2.1-dev.4.2 None)


[√] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at D:\Android Sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-Q, build-tools 28.0.3
    • Java binary at: D:\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)
    • All Android licenses accepted.

[√] Android Studio (version 3.3)
    • Android Studio at D:\Android Studio
    • Flutter plugin version 34.0.1
    • Dart plugin version 182.5215
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)

[√] VS Code, 64-bit edition (version 1.28.2)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 2.21.1

[√] Connected device (1 available)
    • Android SDK built for x86 • emulator-5554 • android-x86 • Android 9 (API 28) (emulator)

• No issues found!

I've followed the guide here: https://medium.com/flutter-io/executing-dart-in-the-background-with-flutter-plugins-and-geofencing-2b3e40a1a124
And looked at the code here: https://github.com/talkdirty/android_job_scheduler

Minus the plugin registration since I don't need to use any plugins with the background job.

Any advice would be welcome :)

[nrkramer]

Anyone? Pleeeeeaaaaaasseeeeee :))

[nrkramer]

Bump

[nrkramer]

Bump

[nrkramer]

Bump

[escamoteur]

Hi, sorry for the delay, I just want to check if you could solve this problem.

[iapicca]

Without additional information, we are unfortunately not sure how to resolve this issue. We are therefore reluctantly going to close this bug for now. Please don't hesitate to comment on the bug if you have any more information for us; we will reopen it right away!

Thanks for your contribution.

[nrkramer]

I'll revive this now. No, I was not able to solve this. This seems to me to be an error within the flutter framework where BinaryMessages are not being passed through a MessageChannel to a CoroutineWorker on the android side.

Basically this is the messaging interface we are expecting to see:

[Kotlin starts Dart isolate]
               MethodChannel
[Dart] ------ "initialized" -------> [Kotlin]
[Kotlin] ------ message 1 -------> [Dart]
[Dart] -------- response --------> [Kotlin]
etc..

This is what I am seeing:

[Kotlin starts Dart isolate]
              MethodChannel
[Dart] ------ "initialized" ------- *Message is never received*

The rest of the transaction fails because Kotlin never receives the first message

There is a class called a MethodChannel, that is used to facilitate the passing of information back and forth between the two languages. I suspect (although without much experience of the underlying code itself I couldn't tell you), that somewhere in that class the information is being lost. Remember that the MethodChannel is the pipeline in which we can do RPC-style calls between the two languages. If this pipeline is broken, the entire system fails.

Forgive me if I'm missing the reason this occurs, I'm not terribly well versed in flutter's code. The key takeaways from this problem are thus:

• A coroutine worker is used to spawn a dart isolate
• The message channel between the dart isolate and the coroutine worker seems to be broken
• The entire point of this is to be able to run dart code in the background, on a schedule, using kotlin

[nrkramer]

In lieu of this problem, we may end up just using straight up Kotlin/Obj-C code to run our background actions, but this is kind of annoying since we have an entire framework built up in flutter for doing this cross-platform, and thus would have to duplicate the code into those two langs (and maintain it). Obviously this sounds insane (and it is). So if there's any excuse I can find to make the above code work, I'll take it

[nrkramer]

Please look at https://gist.github.com/nrkramer/71f202302a177a454244c09188334b2b for an example of the message passing interface between the two languages.

[iapicca]

Hi @nrkramer
Can you please provide your updated flutter doctor -v,
your flutter run --verbose
and a complete reproducible minimal code sample
Thank you