[iOS] Navigation event listeners do not fire callbacks - EventChannel bridge issue

[orestislef]

Platform: iOS
Package version: google_navigation_flutter 0.6.5
Device/Simulator: Physical iPhone (iOS 18)
Issue type: Bug

Description

Navigation event listeners (NavInfo, RoadSnappedLocation, RouteChanged, etc.) do not fire callbacks on iOS, despite guidance running successfully and Google's native UI displaying turn-by-turn navigation correctly.

Steps to Reproduce

1. Initialize navigation session
2. Register event listeners (NavInfo, RoadSnappedLocation, etc.) using the standard API
3. Set destination and start guidance
4. Verify guidance is running via GoogleMapsNavigator.isGuidanceRunning() (returns true)
5. Begin moving or simulate movement along route

Expected Behavior

Event listeners should fire callbacks as navigation state changes:

• setNavInfoListener should fire when approaching turns, route changes occur
• setRoadSnappedLocationUpdatedListener should fire on location updates
• setOnRemainingTimeOrDistanceChangedListener should fire as time/distance changes
• Other navigation events should fire as documented

Actual Behavior

No listener callbacks fire on iOS. All listeners register successfully without errors, but callbacks never execute. The StreamSubscription objects are returned successfully, but no events are emitted through the EventChannel.

Evidence

What works:

• Google's native navigation UI displays turn-by-turn instructions correctly
• Route calculation succeeds (status: NavigationRouteStatus.statusOk)
• Guidance starts successfully (isGuidanceRunning() returns true)
• Voice guidance works
• Polling via getCurrentTimeAndDistance() returns correct data
• Map displays route and updates position correctly

What doesn't work:

• setNavInfoListener - callback never fires
• setRoadSnappedLocationUpdatedListener - callback never fires
• setOnRouteChangedListener - callback never fires
• setOnRemainingTimeOrDistanceChangedListener - callback never fires
• setSpeedingUpdatedListener - callback never fires
• setOnArrivalListener - callback never fires
• setOnReroutingListener - callback never fires
• setTrafficUpdatedListener - callback never fires

Code Sample

// Listeners registered before starting guidance
Future<void> setupListeners() async {
  _navInfoSubscription = GoogleMapsNavigator.setNavInfoListener(
    (navInfo) {
      // This callback NEVER fires on iOS
      print('NavInfo received: ${navInfo.navInfo}');
    },
    numNextStepsToPreview: 10,
  );

  _locationSubscription = await GoogleMapsNavigator.setRoadSnappedLocationUpdatedListener(
    (event) async {
      // This callback NEVER fires on iOS
      print('Location: ${event.location}');
    },
  );

  _timeDistanceSubscription = GoogleMapsNavigator.setOnRemainingTimeOrDistanceChangedListener(
    (event) {
      // This callback NEVER fires on iOS
      print('Time/Distance changed');
    },
    remainingTimeThresholdSeconds: 1,
    remainingDistanceThresholdMeters: 1,
  );
}

// Start guidance after listeners are set up
final routeStatus = await GoogleMapsNavigator.setDestinations(destinations);
await GoogleMapsNavigator.startGuidance();

final isRunning = await GoogleMapsNavigator.isGuidanceRunning();
print('Guidance running: $isRunning'); // Prints: true

// Wait for events... but they never arrive

Logs

flutter: Setting up navigation listeners
flutter: NavInfo listener registered
flutter: Location listener registered
flutter: Route changed listener registered
flutter: Time/Distance listener registered
flutter: ALL LISTENERS REGISTERED SUCCESSFULLY
flutter: Route calculation status: NavigationRouteStatus.statusOk
flutter: Route calculated successfully
flutter: Starting guidance...
flutter: Guidance started
flutter: isGuidanceRunning: true
flutter: Guidance is running - listeners should now fire

[Moving along route for 2 minutes - NO CALLBACKS FIRE]

// However, polling works:
final timeAndDistance = await GoogleMapsNavigator.getCurrentTimeAndDistance();
print('Distance: ${timeAndDistance.distance}m'); // Works - returns correct data

Diagnosis

The issue appears to be in the iOS EventChannel bridge between native code and Flutter. The native iOS Navigation SDK receives NavInfo data (proven by Google's native UI working correctly), but the Flutter plugin does not forward these events to Dart callbacks.

Comparison with official example app: The example app in the repository does not use setNavInfoListener for iOS, which suggests this feature may not be fully implemented or tested on iOS.

Workaround

Currently using polling as a workaround:

Timer.periodic(Duration(seconds: 1), (timer) async {
  try {
    final data = await GoogleMapsNavigator.getCurrentTimeAndDistance();
    // Use data.time and data.distance
  } catch (e) {
    // Handle error
  }
});

This provides ETA and distance but not turn-by-turn instructions, maneuvers, or other NavInfo data that is only available through the listener.

Request

Please investigate the iOS EventChannel implementation for navigation event listeners. All listener registration methods return StreamSubscription objects successfully, but events are not being emitted. This prevents developers from building custom navigation UIs on iOS while still being able to use Google's native UI as a fallback.

Environment

flutter doctor -v output:
[✓] Flutter (Channel stable, 3.24.5)
[✓] Xcode - develop for iOS and macOS (Xcode 16.2)
[✓] iOS device (iPhone - iOS 18)

Package:
google_navigation_flutter: ^0.6.5

iOS Deployment Target: 15.0

Additional Context

This issue affects production applications that need custom navigation UIs. While Google's native UI works well, many apps require branded/custom overlays with specific styling and additional information displays. The polling workaround provides basic ETA/distance but lacks access to turn instructions, maneuvers, remaining steps, and other critical NavInfo fields.

[illuminati1911]

@orestislef Thank you for comprehensive and very clear bug report. We'll investigate this.

[illuminati1911]

Comparison with official example app: The example app in the repository does not use setNavInfoListener for iOS, which suggests this feature may not be fully implemented or tested on iOS.

@orestislef If you go to the "Navigation" page in our example app it uses those "set listener" methods to setup listeners and based on my testing they all seem to work. That specific page does not use setNavInfoListener function but when I was testing this I added it as well and I can receive the events normally.

Could you use our example app with simulated navigation and check the listener page within the example application to see if those event have been received there? You can get there on example app "Navigation" page by selecting Options -> Navigation -> Show listeners and it should look like this:

[orestislef]

Hey, I've been debugging this issue for a while and found something interesting.

So I implemented all the listeners exactly like your example app - registered them right after initializeNavigationSession(), used method references instead of lambdas, added the thresholds, etc. Tested on both Android and iOS.

Here's what I found:

Android: Listeners work perfectly BUT only when setNavigationUIEnabled(true). If I set it to false, all listeners go completely silent. No events at all.

iOS: Listeners don't work period. Doesn't matter if NavigationUI is true or false, if I use simulation mode, debug vs release build - nothing. Zero events from any listener.

I'm registering these 10 listeners following your example:

• NavInfo
• RoadSnappedLocation
• OnArrival
• SpeedingUpdated
• OnRerouting
• TrafficUpdated
• OnRouteChanged
• RemainingTimeOrDistance (with thresholds)
• RoadSnappedRawLocation
• GpsAvailability

Navigation itself works fine on iOS - routes calculate, guidance starts, voice works, native UI displays correctly. The listeners just never fire.

On Android everything fires as expected when NavigationUI is enabled.

Currently using getCurrentTimeAndDistance() polling as a workaround on iOS but that only gives me ETA/distance, no turn-by-turn data or arrival events.

Is setNavigationUIEnabled(true) actually required for listeners to work? And is the iOS EventChannel bridge missing or something? Would really appreciate any insight on this.

Package version: google_navigation_flutter ^0.6.5

[illuminati1911]

Hey @orestislef . Thank you for the additional information. I understand that you implemented your code and listener logic following the example app, but in order to help me investigate this issue, could you also still test if the listeners do fire on the example app itself?

You run it by cloning this repository and following the instruction in the example folder:
https://github.com/googlemaps/flutter-navigation-sdk/tree/main/example

I tested these scenarios locally on our example app on both platforms. Listeners seem to work on both iOS and Android. Turning navigation UI on/off didn't have an impact to the listeners on Android