flutter_services_binding

A subset of WidgetsFlutterBinding specifically for initializing the ServicesBinding.

When executing runApp within a custom Zone with zoneValues derived from the underlying platform we rely on WidgetsFlutterBinding.ensureInitialized():

final token = Object();
void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final value = await _getPlatformValue();
  runZoned(
    () => runApp(MyApp()),
    zoneValues: {token: value},
  );
}

This appears to work as expected, however, because WidgetsFlutterBinding also initializes other bindings like GestureBinding the zoneValue is not accessible within onPressed callbacks:

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print(Zone.current[token]); // OK
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: ElevatedButton(
            onPressed: () {
              print(Zone.current[token]); // NULL
            },
            child: Text('Click Me'),
          ),
        ),
      ),
    );
  }
}

FlutterServicesBinding provides an API to initialize the ServicesBinding and SchedulerBinding independently of the remaining bindings in order to support accessing data from the underlying platform before runApp but without initializing the WidgetsBinding instance within the root Zone.

final token = Object();
void main() async {
  FlutterServicesBinding.ensureInitialized();
  final value = await _getPlatformValue();
  runZoned(
    () => runApp(MyApp()),
    zoneValues: {token: value},
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    print(Zone.current[token]); // OK
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: ElevatedButton(
            onPressed: () {
              print(Zone.current[token]); // OK
            },
            child: Text('Click Me'),
          ),
        ),
      ),
    );
  }
}