fix camera streaming may failed to work on IOS. refer to PR flutter#8733

Author: chaos

packages/camera/camera_avfoundation/ios/camera_avfoundation/Sources/camera_avfoundation/CameraPlugin.swift

@@ -307,8 +307,8 @@ extension CameraPlugin: FCPCameraApi {
   public func startImageStream(completion: @escaping (FlutterError?) -> Void) {
     captureSessionQueue.async { [weak self] in
       guard let strongSelf = self else { return }
-      strongSelf.camera?.startImageStream(with: strongSelf.messenger)
-      completion(nil)
+      strongSelf.camera?
+        .startImageStream(with: strongSelf.messenger, completion: completion)
     }
   }
 

packages/camera/camera_avfoundation/ios/camera_avfoundation/Sources/camera_avfoundation_objc/FLTCam.m

@@ -845,13 +845,17 @@ - (CVPixelBufferRef)copyPixelBuffer {
 
 - (void)startVideoRecordingWithCompletion:(void (^)(FlutterError *_Nullable))completion
                     messengerForStreaming:(nullable NSObject<FlutterBinaryMessenger> *)messenger {
-  if (!_isRecording) {
-    if (messenger != nil) {
-      [self startImageStreamWithMessenger:messenger];
-    }
+  if (_isRecording){
+    completion([FlutterError errorWithCode:@"Error"
+                                    message:@"Video is already recording"
+                                    details:nil]);
+    return;
+  }
 
+  // Main logic to setup the video recording in a block to reuse in the completion block.
+  void (^videoRecordingSetupWithCompletion)(void) = ^void(void) {
     NSError *error;
-    _videoRecordingPath = [self getTemporaryFilePathWithExtension:@"mp4"
+    self->_videoRecordingPath = [self getTemporaryFilePathWithExtension:@"mp4"
                                                         subfolder:@"videos"
                                                            prefix:@"REC_"
                                                             error:error];
@@ -871,20 +875,25 @@ - (void)startVideoRecordingWithCompletion:(void (^)(FlutterError *_Nullable))com
     // didOutputSampleBuffer had chance to call startWriting and lag at start of video
     // https://github.com/flutter/flutter/issues/132016
     // https://github.com/flutter/flutter/issues/151319
-    [_videoWriter startWriting];
-    _isFirstVideoSample = YES;
-    _isRecording = YES;
-    _isRecordingPaused = NO;
-    _videoTimeOffset = CMTimeMake(0, 1);
-    _audioTimeOffset = CMTimeMake(0, 1);
-    _videoIsDisconnected = NO;
-    _audioIsDisconnected = NO;
+    [self->_videoWriter startWriting];
+    self->_isFirstVideoSample = YES;
+    self->_isRecording = YES;
+    self->_isRecordingPaused = NO;
+    self->_videoTimeOffset = CMTimeMake(0, 1);
+    self->_audioTimeOffset = CMTimeMake(0, 1);
+    self->_videoIsDisconnected = NO;
+    self->_audioIsDisconnected = NO;
     completion(nil);
-  } else {
-    completion([FlutterError errorWithCode:@"Error"
-                                   message:@"Video is already recording"
-                                   details:nil]);
+  };
+  
+  if (messenger != nil) {
+    [self startImageStreamWithMessenger:messenger
+                             completion:^(FlutterError *_Nullable error) {
+                               videoRecordingSetupWithCompletion();
+                             }];
+    return;
   }
+  videoRecordingSetupWithCompletion();
 }
 
 - (void)stopVideoRecordingWithCompletion:(void (^)(NSString *_Nullable,
@@ -1176,14 +1185,17 @@ - (void)setExposureOffset:(double)offset {
   [_captureDevice unlockForConfiguration];
 }
 
-- (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger {
+- (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger
+                           completion:(void (^)(FlutterError *))completion {
   [self startImageStreamWithMessenger:messenger
                    imageStreamHandler:[[FLTImageStreamHandler alloc]
-                                          initWithCaptureSessionQueue:_captureSessionQueue]];
+                                          initWithCaptureSessionQueue:_captureSessionQueue]
+                           completion:completion];
 }
 
 - (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger
-                   imageStreamHandler:(FLTImageStreamHandler *)imageStreamHandler {
+                   imageStreamHandler:(FLTImageStreamHandler *)imageStreamHandler
+                           completion:(void (^)(FlutterError *))completion {
   if (!_isStreamingImages) {
     id<FLTEventChannel> eventChannel = [FlutterEventChannel
         eventChannelWithName:@"plugins.flutter.io/camera_avfoundation/imageStream"
@@ -1196,19 +1208,27 @@ - (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messen
     [threadSafeEventChannel setStreamHandler:_imageStreamHandler
                                   completion:^{
                                     typeof(self) strongSelf = weakSelf;
-                                    if (!strongSelf) return;
+                                    if (!strongSelf) {
+                                      completion(nil);
+                                      return;
+                                    }
 
                                     dispatch_async(strongSelf.captureSessionQueue, ^{
                                       // cannot use the outter strongSelf
                                       typeof(self) strongSelf = weakSelf;
-                                      if (!strongSelf) return;
+                                      if (!strongSelf) {
+                                        completion(nil);
+                                        return;
+                                      }
 
                                       strongSelf.isStreamingImages = YES;
                                       strongSelf.streamingPendingFramesCount = 0;
+                                      completion(nil);
                                     });
                                   }];
   } else {
     [self reportErrorMessage:@"Images from camera are already streaming!"];
+    completion(nil);
   }
 }
 

packages/camera/camera_avfoundation/ios/camera_avfoundation/Sources/camera_avfoundation_objc/include/camera_avfoundation/FLTCam.h

@@ -99,7 +99,8 @@ NS_ASSUME_NONNULL_BEGIN
        withCompletion:(void (^)(FlutterError *_Nullable))completion
     NS_SWIFT_NAME(setFocusPoint(_:completion:));
 - (void)setExposureOffset:(double)offset;
-- (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger;
+- (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger
+                           completion:(nonnull void (^)(FlutterError *_Nullable))completion;
 - (void)stopImageStream;
 - (void)setZoomLevel:(CGFloat)zoom withCompletion:(void (^)(FlutterError *_Nullable))completion;
 - (void)setUpCaptureSessionForAudioIfNeeded;

packages/camera/camera_avfoundation/ios/camera_avfoundation/Sources/camera_avfoundation_objc/include/camera_avfoundation/FLTCam_Test.h

@@ -51,6 +51,7 @@
 
 /// Start streaming images.
 - (void)startImageStreamWithMessenger:(NSObject<FlutterBinaryMessenger> *)messenger
-                   imageStreamHandler:(FLTImageStreamHandler *)imageStreamHandler;
+                   imageStreamHandler:(FLTImageStreamHandler *)imageStreamHandler
+                           completion:(void (^)(FlutterError *))completion;
 
 @end