Switch Cameras with Avcapturesession

Switch front/back camera with AVCaptureSession

What you need to do is reconfigure your AVCaptureSession

Here is what i'm using:

// note that `AVCaptureSession * session`
//
if(session)
{
    [session beginConfiguration];

    AVCaptureInput *currentCameraInput = [session.inputs objectAtIndex:0];

    [session removeInput:currentCameraInput];

    AVCaptureDevice *newCamera = nil;

    if(((AVCaptureDeviceInput*)currentCameraInput).device.position == AVCaptureDevicePositionBack)
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
    }
    else
    {
        newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
    }

    NSError *err = nil;

    AVCaptureDeviceInput *newVideoInput = [[AVCaptureDeviceInput alloc] initWithDevice:newCamera error:&err];

    if(!newVideoInput || err)
    {
        NSLog(@"Error creating capture device input: %@", err.localizedDescription);
    }
    else
    {
        [session addInput:newVideoInput];
    }

    [session commitConfiguration];
}

// make sure you have this method in your class
//
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position
{
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for (AVCaptureDevice *device in devices)
    {
        if ([device position] == position)
            return device;
    }
    return nil;
}

How do I implement camera changing from front to back camera

Your problem is that you are not checking if you can add input and/or output before adding them to your capture session. Btw you don't need to setup the preview layer again when switching your camera and you need only one captureDevice:

if captureSession.canAddInput(captureDeviceInput) {
    captureSession.addInput(captureDeviceInput)
} 

and

if captureSession.canAddOutput(photoOutPut) {
    captureSession.addOutput(photoOutPut)
}

Your CollectionViewCell code should look something like this:

class MainCameraCollectionViewCell: UICollectionViewCell, AVCapturePhotoCaptureDelegate {
    private var captureSession = AVCaptureSession()
    private var sessionQueue: DispatchQueue!
    private var captureDevice: AVCaptureDevice!
    private  var photoOutPut: AVCapturePhotoOutput!
    private var cameraPreviewLayer: AVCaptureVideoPreviewLayer!
    var image: UIImage?
    var usingFrontCamera = false
    override func awakeFromNib() {
        super.awakeFromNib()
        setupCaptureSession()
        setupDevice()
        setupInput()
        setupPreviewLayer()
        startRunningCaptureSession()
    }
    func setupCaptureSession(){
        captureSession.sessionPreset = .photo
        sessionQueue = DispatchQueue(label: "session queue")
    }
    func setupDevice(usingFrontCamera: Bool = false){
        sessionQueue.async {
            let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: .video, position: .unspecified)
            let devices = deviceDiscoverySession.devices
            for device in devices {
                if usingFrontCamera && device.position == .front {
                    self.captureDevice = device
                } else if device.position == .back {
                    self.captureDevice = device
                }
            }
        }
    }
    func setupInput() {
        sessionQueue.async {
            do {
                let captureDeviceInput = try AVCaptureDeviceInput(device: self.captureDevice)
                if self.captureSession.canAddInput(captureDeviceInput) {
                    self.captureSession.addInput(captureDeviceInput)
                }
                self.photoOutPut = AVCapturePhotoOutput()
                self.photoOutPut.setPreparedPhotoSettingsArray([AVCapturePhotoSettings(format:[AVVideoCodecKey: AVVideoCodecType.jpeg])], completionHandler: nil)
                if self.captureSession.canAddOutput(self.photoOutPut) {
                    self.captureSession.addOutput(self.photoOutPut)
                }
            } catch {
                print(error)
            }
        }
    }
    func setupPreviewLayer() {
        cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        cameraPreviewLayer.videoGravity = .resizeAspectFill
        cameraPreviewLayer.connection?.videoOrientation = .portrait
        cameraPreviewLayer.frame = UIScreen.main.bounds
        layer.insertSublayer(cameraPreviewLayer, at: 0)
    }
    func startRunningCaptureSession() {
        captureSession.startRunning()
    }
    @IBAction func cameraButton_TouchUpInside(_ sender: Any) {
        let settings = AVCapturePhotoSettings()
        photoOutPut.capturePhoto(with: settings, delegate: self)
    }
    //Flip to front and back camera
    @IBAction func FlipThe_camera(_ sender: UIButton) {
        captureSession.beginConfiguration()
        if let inputs = captureSession.inputs as? [AVCaptureDeviceInput] {
            for input in inputs {
                captureSession.removeInput(input)
            }
        }
        usingFrontCamera = !usingFrontCamera
        setupCaptureSession()
        setupDevice(usingFrontCamera: usingFrontCamera)
        setupInput()
        captureSession.commitConfiguration()
        startRunningCaptureSession()
    }
}

Sample project

How can I switch between 11 pro cameras using AVFoundation in Xcode

Welcome!

Check you this initializer for AVCaptureDevice. You can specify the DeviceType you want to use, like .builtInUltraWideCamera or .builtInTelephotoCamera.

You can use a AVCaptureDevice.DiscoverySession to get a list of all capture devices available to your app.

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