[camera] Guard CameraController value updates after dispose

packages/camera/camera/CHANGELOG.md

@@ -1,5 +1,6 @@
-## NEXT
+## 0.12.1
 
+* Fixes a crash where a `CameraController` could update its value after being disposed, throwing "A CameraController was used after being disposed." (see [flutter/flutter#184959](https://github.com/flutter/flutter/issues/184959)).
 * Updates minimum supported SDK version to Flutter 3.38/Dart 3.10.
 
 ## 0.12.0+1

packages/camera/camera/lib/src/camera_controller.dart

@@ -337,7 +337,9 @@ class CameraController extends ValueNotifier<CameraValue> {
       _deviceOrientationSubscription ??= CameraPlatform.instance
           .onDeviceOrientationChanged()
           .listen((DeviceOrientationChangedEvent event) {
-            value = value.copyWith(deviceOrientation: event.orientation);
+            if (!_isDisposed) {
+              value = value.copyWith(deviceOrientation: event.orientation);
+            }
           });
 
       _cameraId = await CameraPlatform.instance.createCameraWithSettings(
@@ -355,7 +357,9 @@ class CameraController extends ValueNotifier<CameraValue> {
 
       unawaited(
         CameraPlatform.instance.onCameraError(_cameraId).first.then((CameraErrorEvent event) {
-          value = value.copyWith(errorDescription: event.description);
+          if (!_isDisposed) {
+            value = value.copyWith(errorDescription: event.description);
+          }
         }),
       );
 
@@ -364,25 +368,20 @@ class CameraController extends ValueNotifier<CameraValue> {
         imageFormatGroup: imageFormatGroup ?? ImageFormatGroup.unknown,
       );
 
-      value = value.copyWith(
-        isInitialized: true,
-        description: description,
-        previewSize: await initializeCompleter.future.then(
-          (CameraInitializedEvent event) => Size(event.previewWidth, event.previewHeight),
-        ),
-        exposureMode: await initializeCompleter.future.then(
-          (CameraInitializedEvent event) => event.exposureMode,
-        ),
-        focusMode: await initializeCompleter.future.then(
-          (CameraInitializedEvent event) => event.focusMode,
-        ),
-        exposurePointSupported: await initializeCompleter.future.then(
-          (CameraInitializedEvent event) => event.exposurePointSupported,
-        ),
-        focusPointSupported: await initializeCompleter.future.then(
-          (CameraInitializedEvent event) => event.focusPointSupported,
-        ),
-      );
+      final CameraInitializedEvent event = await initializeCompleter.future;
+
+      // The controller may be disposed while awaiting initialization above.
+      if (!_isDisposed) {
+        value = value.copyWith(
+          isInitialized: true,
+          description: description,
+          previewSize: Size(event.previewWidth, event.previewHeight),
+          exposureMode: event.exposureMode,
+          focusMode: event.focusMode,
+          exposurePointSupported: event.exposurePointSupported,
+          focusPointSupported: event.focusPointSupported,
+        );
+      }
     } on PlatformException catch (e) {
       throw CameraException(e.code, e.message);
     } finally {

packages/camera/camera/pubspec.yaml

@@ -4,7 +4,7 @@ description: A Flutter plugin for controlling the camera. Supports previewing
   Dart.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.12.0+1
+version: 0.12.1
 
 environment:
   sdk: ^3.10.0

packages/camera/camera/test/camera_test.dart

@@ -3428,6 +3428,54 @@ void main() {
       expect(cameraController.value.errorDescription, mockOnCameraErrorEvent.description);
     });
   });
+
+  group('does not update value after dispose', () {
+    test('when initialization completes after dispose', () async {
+      final platform = MockDelayedInitializeCameraPlatform();
+      CameraPlatform.instance = platform;
+
+      final cameraController = CameraController(
+        const CameraDescription(
+          name: 'cam',
+          lensDirection: CameraLensDirection.back,
+          sensorOrientation: 90,
+        ),
+        ResolutionPreset.max,
+      );
+
+      final Future<void> initializeFuture = cameraController.initialize();
+      await pumpEventQueue();
+
+      // Dispose while initialization is still in flight, then let it complete.
+      final Future<void> disposeFuture = cameraController.dispose();
+      platform.initializeCameraCompleter.complete();
+
+      await expectLater(initializeFuture, completes);
+      await disposeFuture;
+    });
+
+    test('when a camera error event arrives after dispose', () async {
+      final platform = MockControllableErrorCameraPlatform();
+      CameraPlatform.instance = platform;
+
+      final cameraController = CameraController(
+        const CameraDescription(
+          name: 'cam',
+          lensDirection: CameraLensDirection.back,
+          sensorOrientation: 90,
+        ),
+        ResolutionPreset.max,
+      );
+      await cameraController.initialize();
+      await cameraController.dispose();
+
+      // A camera error arriving after dispose must not update `value`.
+      platform.cameraErrorController.add(const CameraErrorEvent(13, 'late error'));
+      await pumpEventQueue();
+
+      expect(cameraController.value.errorDescription, isNull);
+    });
+  });
 }
 
 class MockCameraPlatform extends Mock with MockPlatformInterfaceMixin implements CameraPlatform {
@@ -3611,3 +3659,26 @@ class MockCameraDescription extends CameraDescription {
   @override
   String get name => 'back';
 }
+
+/// A platform whose [initializeCamera] only completes once
+/// [initializeCameraCompleter] is completed, so a test can dispose the
+/// controller while initialization is still in flight.
+class MockDelayedInitializeCameraPlatform extends MockCameraPlatform {
+  final Completer<void> initializeCameraCompleter = Completer<void>();
+
+  @override
+  Future<void> initializeCamera(
+    int? cameraId, {
+    ImageFormatGroup? imageFormatGroup = ImageFormatGroup.unknown,
+  }) => initializeCameraCompleter.future;
+}
+
+/// A platform whose camera error events are driven by [cameraErrorController],
+/// so a test can emit an error after the controller has been disposed.
+class MockControllableErrorCameraPlatform extends MockCameraPlatform {
+  final StreamController<CameraErrorEvent> cameraErrorController =
+      StreamController<CameraErrorEvent>.broadcast();
+
+  @override
+  Stream<CameraErrorEvent> onCameraError(int cameraId) => cameraErrorController.stream;
+}