How to get FletService.init() to fire on Android for a custom Service Extension? (Flet 0.84)

[youngnckk12-design]

Question

Summary

Custom Flet Service Extension builds and installs correctly, but the Dart FletService.init() method is never called at runtime. No debugPrint output reaches logcat despite flet build confirming the extension was found and registered.

Environment

• Flet: 0.84.0
• Platform: Android
• Build: flet build aab via GitHub Actions
• Extension: Custom Service Extension wrapping in_app_purchase: ^3.2.0

What works ✅

• Extension installs: pip install ./flet-billing succeeds for all 4 Android ABIs
• Build log confirms:
  Found Flutter extension at .../build/flutter-packages/flet_billing
  Registered Flutter user extensions ✅
• Python import works: from flet_billing import FletBilling succeeds
• Constructor works: FletBilling(product_id="...", ...) returns without error
• page.services.append(billing) executes without error
• page.update() is called immediately after append
• App runs, no red error screen, no Flutter exceptions
• serious_python: CPython loaded and Py_Initialize() complete successfully in logcat

What doesn't work ❌

• BillingService.init() (Dart) is never called
• I added debugPrint("[flet-billing] init() called") as the very first line of init() — zero output in logcat across three different builds
• Calling billing.buy() from Python → self.invoke_method("buy") never reaches Dart's _invokeMethod listener
• Captured via: adb logcat flutter:V *:W > out.txt

Extension structure

Python side (src/flet_billing/flet_billing.py):

import flet as ft

@ft.control("flet_billing")
class FletBilling(ft.Service):
    product_id: str = "my_product_id"
    auto_consume: bool = False
    on_purchase_success: Optional[Callable] = None
    on_purchase_error: Optional[Callable] = None
    on_purchase_cancelled: Optional[Callable] = None

    def buy(self) -> None:
        self.invoke_method("buy")

    def restore(self) -> None:
        self.invoke_method("restore")

Dart side — extension.dart:

import 'package:flet/flet.dart';
import 'package:flutter/widgets.dart';
import 'billing_service.dart';

class Extension extends FletExtension {
  @override
  void ensureInitialized() {}

  @override
  FletService? createService(Control control) {
    switch (control.type) {
      case "flet_billing":
        return BillingService(control: control);
      default:
        return null;
    }
  }

  @override
  Widget? createWidget(Key? key, Control control) {
    return null;
  }
}

Dart side — billing_service.dart (abbreviated, matches haptic_feedback.dart reference pattern):

class BillingService extends FletService {
  BillingService({required super.control});

  @override
  void init() {
    super.init();
    debugPrint("[flet-billing] init() called");  // never appears
    control.addInvokeMethodListener(_onInvokeMethod);
    // ... iap setup ...
  }

  Future<dynamic> _onInvokeMethod(String name, dynamic args) async {
    debugPrint("[flet-billing] invoke: $name");  // never appears
    // ...
  }

  @override
  void dispose() {
    control.removeInvokeMethodListener(_onInvokeMethod);
    super.dispose();
  }
}

Python usage in app's main.py:

from flet_billing import FletBilling

def main(page: ft.Page):
    billing = FletBilling(
        product_id="my_product_id",
        on_purchase_success=handle_success,
        on_purchase_error=handle_error,
        on_purchase_cancelled=handle_cancel,
    )
    page.services.append(billing)
    page.update()
    # ... rest of app

pyproject.toml (extension)

[project]
name = "flet-billing"
version = "0.1.0"
requires-python = ">=3.9"
dependencies = ["flet>=0.80.0"]

[tool.flet.extensions.flet_billing]
path = "flutter/flet_billing"

[tool.setuptools.packages.find]
where = ["src"]

[tool.setuptools.package-data]
"flutter.flet_billing" = ["**/*"]

pyproject.toml (app)

[project]
name = "myapp"
version = "1.0.0"
dependencies = ["flet-billing"]

[tool.flet]
app.module = "main"

[tool.flet.dev_packages]
flet-billing = "./flet-billing"

[tool.flet.flutter.pubspec.dependencies]
in_app_purchase = "^3.2.0"

What I've tried

1. Compared against haptic_feedback.dart and flet-permission-handler — code now matches reference pattern (super.init(), super.dispose(), Future<dynamic> / dynamic signature)
2. Tried both page.services.append(billing) with and without subsequent page.update()
3. Verified pip install output and build registration in CI logs — both clean
4. Verified APK contains extension's Flutter code via build output paths
5. Confirmed logcat capture is working (other Flutter logs appear fine)

Question

In Flet 0.84, what triggers FletService.init() to fire on a service added to page.services? Is there a registration step I'm missing between Extension.createService() being registered and the actual instantiation? Or is the issue likely in my @ft.control("flet_billing") Python decorator — should it be "FletBilling" (PascalCase matching the class name) instead?

Full extension source available if helpful.

Thanks 🙏

Code sample

No response

Error message

No response

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• I have searched for answers to my question both in the issues and in previous discussions.