fix: ios crash camera permissions

CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.1.44
+
+- **Critical Bug Fix**: Fix SIGSEGV crash when YOLOView is disposed while TensorFlow Lite inference is running
+  - **Root Cause**: Race condition where `onFrame` callback continued executing after `stop()` cleared resources and closed the TensorFlow Lite interpreter
+  - **Fix**: Added `@Volatile` `isStopped` flag that is checked at multiple points in `onFrame` to prevent accessing closed resources
+
 ## 0.1.43
 
 - **Enhancement**: Unify classification output format across all platforms to use official Results.summary() format
@@ -53,7 +59,6 @@
 ## 0.1.38
 
 - **Bug Fix**: iOS performance metrics not updating in `YOLOView`
-
   - Moved EventChannel subscription from `initState` to `_onPlatformViewCreated` to ensure native channel readiness on iOS
   - Aligned streaming config key with iOS by renaming `throttleInterval` to `throttleIntervalMs` when sending params
   - iOS now sources performance metrics from the latest inference result: `processingTimeMs = result.speed * 1000`, `fps = result.fps`

android/src/main/kotlin/com/ultralytics/yolo/YOLOPlatformView.kt

@@ -5,6 +5,7 @@ package com.ultralytics.yolo
 import android.content.Context
 import android.util.Log
 import android.view.View
+import androidx.core.content.ContextCompat
 import androidx.lifecycle.LifecycleOwner
 import io.flutter.plugin.common.EventChannel
 import io.flutter.plugin.common.MethodCall
@@ -49,6 +50,7 @@ class YOLOPlatformView(
     private var retryRunnable: Runnable? = null
 
     init {
+        Log.d(TAG, "YOLOPlatformView[$viewId] INIT BLOCK STARTING")
         val dartViewIdParam = creationParams?.get("viewId")
         viewUniqueId = dartViewIdParam as? String ?: viewId.toString().also {
             Log.w(TAG, "YOLOPlatformView[$viewId init]: Using platform int viewId '$it' as fallback")
@@ -85,14 +87,19 @@ class YOLOPlatformView(
         // Configure YOLOView streaming functionality
         setupYOLOViewStreaming(creationParams)
 
-        // Initialize camera
-        Log.d(TAG, "Attempting early camera initialization")
-        yoloView.initCamera()
-
-        // Notify lifecycle if available
+        // Notify lifecycle FIRST before initializing camera
+        // This ensures lifecycle owner is set before camera tries to start
         if (context is LifecycleOwner) {
             Log.d(TAG, "Initial context is a LifecycleOwner, notifying YOLOView")
             yoloView.onLifecycleOwnerAvailable(context)
+            // initCamera will be called by onLifecycleOwnerAvailable if permissions are granted
+            // But we also call it here as a fallback
+            Log.d(TAG, "Attempting camera initialization after lifecycle owner setup")
+            yoloView.initCamera()
+        } else {
+            Log.w(TAG, "Context is not a LifecycleOwner, camera may not start")
+            // Still try to initialize camera - it will request permissions if needed
+            yoloView.initCamera()
         }
 
         try {
@@ -105,12 +112,17 @@ class YOLOPlatformView(
             // Set up model loading callback
             yoloView.setOnModelLoadCallback { success ->
                 if (success) {
-                    Log.d(TAG, "Model loaded successfully")
                     initialized = true
-                    // Start streaming if not already started
                     startStreaming()
+                    val context = yoloView.context
+                    val hasPermissions = android.Manifest.permission.CAMERA.let { permission ->
+                        android.content.pm.PackageManager.PERMISSION_GRANTED == 
+                        ContextCompat.checkSelfPermission(context, permission)
+                    }
+                    if (hasPermissions) {
+                        yoloView.startCamera()
+                    }
                 } else {
-                    Log.w(TAG, "Failed to load model")
                     initialized = true
                 }
             }
@@ -418,6 +430,11 @@ class YOLOPlatformView(
                     Log.d(TAG, "Camera and inference stopped")
                     result.success(null)
                 }
+                "restartCamera" -> {
+                    Log.d(TAG, "Restarting camera (requested from Flutter)")
+                    yoloView.startCamera()
+                    result.success(null)
+                }
                 "captureFrame" -> {
                     val imageData = yoloView.captureFrame()
                     if (imageData != null) {

android/src/main/kotlin/com/ultralytics/yolo/YOLOView.kt

@@ -207,7 +207,11 @@ class YOLOView @JvmOverloads constructor(
 
     // New fields for proper teardown:
     private var cameraExecutor: ExecutorService? = null
-    private var imageAnalysisUseCase: ImageAnalysis? = null    
+    private var imageAnalysisUseCase: ImageAnalysis? = null
+
+    // Flag to track if the view is stopped/disposed to prevent race conditions
+    @Volatile
+    private var isStopped = false    
 
     // Zoom related
     private var currentZoomRatio = 1.0f
@@ -419,7 +423,10 @@ class YOLOView @JvmOverloads constructor(
                     this.modelName = modelPath.substringAfterLast("/")
                     modelLoadCallback?.invoke(true)
                     callback?.invoke(true)
-                    Log.d(TAG, "Model loaded successfully: $modelPath")
+                    // Ensure camera starts after model loads if it's not already running
+                    if (allPermissionsGranted() && lifecycleOwner != null && (camera == null || isStopped)) {
+                        startCamera()
+                    }
                 }
             } catch (e: Exception) {
                 Log.w(TAG, "Failed to load model: $modelPath. Camera will run without inference.", e)
@@ -466,21 +473,20 @@ class YOLOView @JvmOverloads constructor(
      */
     fun onLifecycleOwnerAvailable(owner: LifecycleOwner) {
         this.lifecycleOwner = owner
-        // Register as a lifecycle observer to handle lifecycle events
         owner.lifecycle.addObserver(this)
 
-        // If camera was requested but couldn't start due to missing lifecycle owner, try again
-        if (allPermissionsGranted()) {
+        if (allPermissionsGranted() && (camera == null || isStopped)) {
             startCamera()
         }
-        Log.d(TAG, "LifecycleOwner set: ${owner.javaClass.simpleName}")
     }
 
     // region camera init
 
     fun initCamera() {
         if (allPermissionsGranted()) {
-            startCamera()
+            if (lifecycleOwner != null && (camera == null || isStopped)) {
+                startCamera()
+            }
         } else {
             val activity = context as? Activity ?: return
             ActivityCompat.requestPermissions(
@@ -510,7 +516,7 @@ class YOLOView @JvmOverloads constructor(
     }
 
     fun startCamera() {
-        Log.d(TAG, "Starting camera...")
+        isStopped = false
 
         try {
             cameraProviderFuture = ProcessCameraProvider.getInstance(context)
@@ -605,9 +611,27 @@ class YOLOView @JvmOverloads constructor(
 
     // Lifecycle methods from DefaultLifecycleObserver
     override fun onStart(owner: LifecycleOwner) {
-        Log.d(TAG, "Lifecycle onStart")
+        Log.d(TAG, "Lifecycle onStart - restarting camera if stopped")
         if (allPermissionsGranted()) {
-            startCamera()
+            // Always restart camera on start if it's stopped or null
+            // This ensures camera resumes when navigating back
+            if (isStopped || camera == null) {
+                Log.d(TAG, "Camera is stopped or null, restarting on onStart")
+                startCamera()
+            } else {
+                Log.d(TAG, "Camera is already running, no restart needed")
+            }
+        }
+    }
+
+    override fun onResume(owner: LifecycleOwner) {
+        Log.d(TAG, "Lifecycle onResume - ensuring camera is running")
+        if (allPermissionsGranted()) {
+            // Double-check camera is running on resume
+            if (isStopped || camera == null) {
+                Log.d(TAG, "Camera not running on resume, restarting...")
+                startCamera()
+            }
         }
     }
 
@@ -619,6 +643,13 @@ class YOLOView @JvmOverloads constructor(
     // region onFrame (per frame inference)
 
     private fun onFrame(imageProxy: ImageProxy) {
+        // Early return if view is stopped to prevent accessing closed resources
+        if (isStopped) {
+            Log.d(TAG, "onFrame: View is stopped, skipping frame processing")
+            imageProxy.close()
+            return
+        }
+
         val w = imageProxy.width
         val h = imageProxy.height
         val orientation = context.resources.configuration.orientation
@@ -630,7 +661,21 @@ class YOLOView @JvmOverloads constructor(
             return
         }
 
+        // Check again after bitmap conversion (in case stop() was called during conversion)
+        if (isStopped) {
+            Log.d(TAG, "onFrame: View stopped during bitmap conversion, skipping inference")
+            imageProxy.close()
+            return
+        }
+
         predictor?.let { p ->
+            // Double-check stopped flag before inference (predictor might be closed)
+            if (isStopped) {
+                Log.d(TAG, "onFrame: View stopped before inference, skipping")
+                imageProxy.close()
+                return
+            }
+
             // Check if we should run inference on this frame
             if (!shouldRunInference()) {
                 Log.d(TAG, "Skipping inference due to frequency control")
@@ -1773,6 +1818,9 @@ class YOLOView @JvmOverloads constructor(
      */
     fun stop() {
         Log.d(TAG, "YOLOView.stop() called - tearing down camera")
+
+        // Set stopped flag first to prevent new frames from being processed
+        isStopped = true
 
         try {
             imageAnalysisUseCase?.clearAnalyzer()
@@ -1811,7 +1859,13 @@ class YOLOView @JvmOverloads constructor(
             cameraExecutor = null
 
             camera = null
-            (predictor as? BasePredictor)?.close()
+
+            // Close predictor safely - ensure no inference is running
+            try {
+                (predictor as? BasePredictor)?.close()
+            } catch (e: Exception) {
+                Log.e(TAG, "Error closing predictor", e)
+            }
             predictor = null
             inferenceCallback = null
             streamCallback = null

example/lib/presentation/screens/camera_inference_screen.dart

@@ -25,6 +25,7 @@ class CameraInferenceScreen extends StatefulWidget {
 
 class _CameraInferenceScreenState extends State<CameraInferenceScreen> {
   late final CameraInferenceController _controller;
+  int _rebuildKey = 0;
 
   @override
   void initState() {
@@ -37,6 +38,24 @@ class _CameraInferenceScreenState extends State<CameraInferenceScreen> {
     });
   }
 
+  @override
+  void didChangeDependencies() {
+    super.didChangeDependencies();
+    // Check if route is current (we've navigated back to this screen)
+    final route = ModalRoute.of(context);
+    if (route?.isCurrent == true) {
+      // Force rebuild when navigating back to ensure camera restarts
+      // The rebuild will create a new YOLOView which will automatically start the camera
+      WidgetsBinding.instance.addPostFrameCallback((_) {
+        if (mounted) {
+          setState(() {
+            _rebuildKey++;
+          });
+        }
+      });
+    }
+  }
+
   @override
   void dispose() {
     _controller.dispose();
@@ -49,12 +68,17 @@ class _CameraInferenceScreenState extends State<CameraInferenceScreen> {
         MediaQuery.of(context).orientation == Orientation.landscape;
 
     return Scaffold(
+      appBar: AppBar(title: const Text('YOLO Camera Inference')),
       body: ListenableBuilder(
         listenable: _controller,
         builder: (context, child) {
           return Stack(
             children: [
-              CameraInferenceContent(controller: _controller),
+              CameraInferenceContent(
+                key: ValueKey('camera_content_$_rebuildKey'),
+                controller: _controller,
+                rebuildKey: _rebuildKey,
+              ),
               CameraInferenceOverlay(
                 controller: _controller,
                 isLandscape: isLandscape,

example/lib/presentation/widgets/camera_inference_content.dart

@@ -8,16 +8,21 @@ import 'model_loading_overlay.dart';
 
 /// Main content widget that handles the camera view and loading states
 class CameraInferenceContent extends StatelessWidget {
-  const CameraInferenceContent({super.key, required this.controller});
+  const CameraInferenceContent({
+    super.key,
+    required this.controller,
+    this.rebuildKey = 0,
+  });
 
   final CameraInferenceController controller;
+  final int rebuildKey;
 
   @override
   Widget build(BuildContext context) {
     if (controller.modelPath != null && !controller.isModelLoading) {
       return YOLOView(
         key: ValueKey(
-          'yolo_view_${controller.modelPath}_${controller.selectedModel.task.name}',
+          'yolo_view_${controller.modelPath}_${controller.selectedModel.task.name}_$rebuildKey',
         ),
         controller: controller.yoloController,
         modelPath: controller.modelPath!,