PlatformException(channel-error) when using shared_preferences on Flutter Desktop

[Vaache]

I’m getting the following error when trying to use the shared_preferences package in a Flutter desktop app (with multiple windows / secondary engine):

PlatformException(channel-error, Unable to establish connection on channel: "dev.flutter.pigeon.shared_preferences_foundation.LegacyUserDefaultsApi.getAll"., null, null)

It looks like the plugin cannot establish a connection to the method channel.
From what I understand, shared_preferences relies on a platform channel that may not be registered when using multiple Flutter engines or secondary windows.

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Questions

1. What exactly does this error mean?
2. Is shared_preferences limited to only the main Flutter engine?
3. How can I make it work in a secondary window / secondary FlutterEngine?
4. Is there a workaround (e.g., registering the plugin manually, or using another approach for storing preferences in additional windows)?

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Environment

• Flutter:
  Flutter 3.35.4

Framework • revision d693b4b9db (9 days ago) • 2025-09-16 14:27:41 +0000
Engine • hash feee8ee8fb8b975dd9990f86d3bda11e6e75faf3 (revision c298091351) (10 days ago) • 2025-09-15 14:04:24.000Z
Tools • Dart 3.9.2 • DevTools 2.48.0

• OS: [macOS/Linux/Windows]
• Package: shared_preferences [version]

[stuartmorgan-g]

This appears to be essentially the same issue as #441, so my comment there applies here as well (although the exact methods are slightly different on macOS, which appears to be the platform this error is coming from).

2. Is shared_preferences limited to only the main Flutter engine?

It should work in any engine where the plugin has been registered.

3. How can I make it work in a secondary window / secondary FlutterEngine?

If you can get access to the engine, you could manually run the plugin registration for any plugins you want to. An API like the one I described in the linked issue would be the easiest way for desktop_multi_window clients to be able to do so.

[boyan01]

AS #58

Because each window created by this plugin has its own dedicated Flutter engine, and method channels cannot be shared between engines, the new window cannot directly call plugins registered with the main Flutter engine.

The solution is to manually register the required plugins.

flutter-plugins/packages/desktop_multi_window/example/windows/runner/flutter_window.cpp

Lines 32 to 38 in 985d816

	DesktopMultiWindowSetWindowCreatedCallback([](void *controller) {
	auto *flutter_view_controller =
	reinterpret_cast<flutter::FlutterViewController *>(controller);
	auto *registry = flutter_view_controller->engine();
	DesktopLifecyclePluginRegisterWithRegistrar(
	registry->GetRegistrarForPlugin("DesktopLifecyclePlugin"));
	});

flutter-plugins/packages/desktop_multi_window/example/macos/Runner/MainFlutterWindow.swift

Lines 15 to 18 in 985d816

	FlutterMultiWindowPlugin.setOnWindowCreatedCallback { controller in
	// Register the plugin which you want access from other isolate.
	DesktopLifecyclePlugin.register(with: controller.registrar(forPlugin: "DesktopLifecyclePlugin"))
	}

flutter-plugins/packages/desktop_multi_window/example/linux/my_application.cc

Lines 65 to 69 in 985d816

	desktop_multi_window_plugin_set_window_created_callback([](FlPluginRegistry* registry){
	g_autoptr(FlPluginRegistrar) desktop_lifecycle_registrar =
	fl_plugin_registry_get_registrar_for_plugin(registry, "DesktopLifecyclePlugin");
	desktop_lifecycle_plugin_register_with_registrar(desktop_lifecycle_registrar);
	});