Attempting to improve performance by changing the initialization process

RCTCamera.m

@@ -65,6 +65,7 @@
   if ((self = [super init])) {
     self.manager = manager;
     [self.manager initializeCaptureSessionInput:AVMediaTypeVideo];
+    [self.manager startSession];
   }
   return self;
 }
@@ -93,6 +94,7 @@
 {
   [super removeFromSuperview];
   [[NSNotificationCenter defaultCenter] removeObserver:self name:UIDeviceOrientationDidChangeNotification object:nil];
+  [self.manager stopSession];
 }
 
 - (void)orientationChanged:(NSNotification *)notification{

RCTCameraManager.h

@@ -69,5 +69,7 @@ typedef NS_ENUM(NSInteger, RCTCameraTorchMode) {
 - (void)capture:(NSDictionary*)options callback:(RCTResponseSenderBlock)callback;
 - (void)initializeCaptureSessionInput:(NSString*)type;
 - (void)stopCapture;
+- (void)startSession;
+- (void)stopSession;
 
 @end

RCTCameraManager.m

@@ -105,47 +105,6 @@ RCT_EXPORT_VIEW_PROPERTY(torchMode, NSInteger);
 
     self.sessionQueue = dispatch_queue_create("cameraManagerQueue", DISPATCH_QUEUE_SERIAL);
 
-    dispatch_async(self.sessionQueue, ^{
-
-
-      if (self.presetCamera == AVCaptureDevicePositionUnspecified) {
-        self.presetCamera = AVCaptureDevicePositionBack;
-      }
-
-      AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
-      if ([self.session canAddOutput:stillImageOutput])
-      {
-        stillImageOutput.outputSettings = @{AVVideoCodecKey : AVVideoCodecJPEG};
-        [self.session addOutput:stillImageOutput];
-        self.stillImageOutput = stillImageOutput;
-      }
-
-      AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
-      if ([self.session canAddOutput:movieFileOutput])
-      {
-        [self.session addOutput:movieFileOutput];
-        self.movieFileOutput = movieFileOutput;
-      }
-
-      AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
-      if ([self.session canAddOutput:metadataOutput]) {
-        [metadataOutput setMetadataObjectsDelegate:self queue:self.sessionQueue];
-        [self.session addOutput:metadataOutput];
-        [metadataOutput setMetadataObjectTypes:metadataOutput.availableMetadataObjectTypes];
-        self.metadataOutput = metadataOutput;
-      }
-
-      __weak RCTCameraManager *weakSelf = self;
-      [self setRuntimeErrorHandlingObserver:[NSNotificationCenter.defaultCenter addObserverForName:AVCaptureSessionRuntimeErrorNotification object:self.session queue:nil usingBlock:^(NSNotification *note) {
-        RCTCameraManager *strongSelf = weakSelf;
-        dispatch_async(strongSelf.sessionQueue, ^{
-          // Manually restarting the session since it must have been stopped due to an error.
-          [strongSelf.session startRunning];
-        });
-      }]];
-
-      [self.session startRunning];
-    });
   }
   return self;
 }
@@ -254,6 +213,62 @@ RCT_EXPORT_METHOD(stopCapture) {
   }
 }
 
+- (void)startSession {
+  dispatch_async(self.sessionQueue, ^{
+    if (self.presetCamera == AVCaptureDevicePositionUnspecified) {
+      self.presetCamera = AVCaptureDevicePositionBack;
+    }
+    
+    AVCaptureStillImageOutput *stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
+    if ([self.session canAddOutput:stillImageOutput])
+    {
+      stillImageOutput.outputSettings = @{AVVideoCodecKey : AVVideoCodecJPEG};
+      [self.session addOutput:stillImageOutput];
+      self.stillImageOutput = stillImageOutput;
+    }
+    
+    AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
+    if ([self.session canAddOutput:movieFileOutput])
+    {
+      [self.session addOutput:movieFileOutput];
+      self.movieFileOutput = movieFileOutput;
+    }
+    
+    AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
+    if ([self.session canAddOutput:metadataOutput]) {
+      [metadataOutput setMetadataObjectsDelegate:self queue:self.sessionQueue];
+      [self.session addOutput:metadataOutput];
+      [metadataOutput setMetadataObjectTypes:metadataOutput.availableMetadataObjectTypes];
+      self.metadataOutput = metadataOutput;
+    }
+    
+    __weak RCTCameraManager *weakSelf = self;
+    [self setRuntimeErrorHandlingObserver:[NSNotificationCenter.defaultCenter addObserverForName:AVCaptureSessionRuntimeErrorNotification object:self.session queue:nil usingBlock:^(NSNotification *note) {
+      RCTCameraManager *strongSelf = weakSelf;
+      dispatch_async(strongSelf.sessionQueue, ^{
+        // Manually restarting the session since it must have been stopped due to an error.
+        [strongSelf.session startRunning];
+      });
+    }]];
+    
+    [self.session startRunning];
+  });
+}
+
+- (void)stopSession {
+  dispatch_async(self.sessionQueue, ^{
+    [self.previewLayer removeFromSuperlayer];
+    [self.session stopRunning];
+    for(AVCaptureInput *input in self.session.inputs) {
+      [self.session removeInput:input];
+    }
+    
+    for(AVCaptureOutput *output in self.session.outputs) {
+      [self.session removeOutput:output];
+    }
+  });
+}
+
 - (void)initializeCaptureSessionInput:(NSString *)type {
   dispatch_async(self.sessionQueue, ^{
     NSError *error = nil;