fix: cancel the previous heading subscription before resubscribing #170

lib/src/widgets/current_location_layer.dart

@@ -480,6 +480,9 @@ class _CurrentLocationLayerState extends State<CurrentLocationLayer>
   }
 
   void _subscriptHeadingStream() {
+    // A dropout leaves the previous subscription live; reassigning without
+    // cancelling would orphan it and keep the sensor running after dispose.
+    _headingSubscription?.cancel();
     final headingStream =
         widget.headingStream ??
         const LocationMarkerDataStreamFactory()
@@ -516,6 +519,9 @@ class _CurrentLocationLayerState extends State<CurrentLocationLayer>
         }
       },
       onError: (error) {
+        if (!mounted) {
+          return;
+        }
         error = widget.errorHandler(error);
         if (error is UnsupportedException) {
           if (kDebugMode) {

test/widgets/current_location_layer_test.dart

@@ -0,0 +1,73 @@
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_map/flutter_map.dart';
+import 'package:flutter_map_location_marker/flutter_map_location_marker.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:latlong2/latlong.dart';
+
+void main() {
+  group('CurrentLocationLayer', () {
+    testWidgets('Should cancel the heading subscription when the layer is '
+        'disposed after a position dropout and recovery', (tester) async {
+      final positions = StreamController<LocationMarkerPosition?>.broadcast();
+      final headings = StreamController<LocationMarkerHeading?>.broadcast();
+      addTearDown(positions.close);
+      addTearDown(headings.close);
+
+      await tester.pumpWidget(_buildApp(positions.stream, headings.stream));
+
+      // A position fix subscribes to the heading stream and readies the layer.
+      positions.add(_position);
+      await tester.pump(const Duration(seconds: 1));
+
+      headings.add(LocationMarkerHeading(heading: 1, accuracy: 0.3));
+      await tester.pump(const Duration(seconds: 1));
+
+      // A dropout resets the status but leaves the heading subscription live.
+      positions.add(null);
+      await tester.pump(const Duration(seconds: 1));
+
+      // The recovery subscribes to the heading stream a second time.
+      positions.add(_position);
+      await tester.pump(const Duration(seconds: 1));
+
+      await tester.pumpWidget(
+        _buildApp(positions.stream, headings.stream, withLayer: false),
+      );
+      await tester.pump(const Duration(seconds: 1));
+
+      // No subscription may outlive the layer, or the sensor never stops.
+      expect(headings.hasListener, isFalse);
+
+      // A late sensor error must not reach the disposed state.
+      headings.addError(Exception('sensor fault'));
+      await tester.pump(const Duration(seconds: 1));
+
+      expect(tester.takeException(), isNull);
+    });
+  });
+}
+
+final _position = LocationMarkerPosition(
+  latitude: 52.52,
+  longitude: 13.405,
+  accuracy: 10,
+);
+
+Widget _buildApp(
+  Stream<LocationMarkerPosition?> positionStream,
+  Stream<LocationMarkerHeading?> headingStream, {
+  bool withLayer = true,
+}) => MaterialApp(
+  home: FlutterMap(
+    options: const MapOptions(initialCenter: LatLng(52.52, 13.405)),
+    children: [
+      if (withLayer)
+        CurrentLocationLayer(
+          positionStream: positionStream,
+          headingStream: headingStream,
+        ),
+    ],
+  ),
+);