How to Add Live Camera Preview to UIView

UPDATED TO SWIFT 5

You can try something like this:

import UIKitimport AVFoundationclass ViewController: UIViewController{    var previewView : UIView!    var boxView:UIView!    let myButton: UIButton = UIButton()    //Camera Capture requiered properties    var videoDataOutput: AVCaptureVideoDataOutput!    var videoDataOutputQueue: DispatchQueue!    var previewLayer:AVCaptureVideoPreviewLayer!    var captureDevice : AVCaptureDevice!    let session = AVCaptureSession()    override func viewDidLoad() {        super.viewDidLoad()        previewView = UIView(frame: CGRect(x: 0,                                           y: 0,                                           width: UIScreen.main.bounds.size.width,                                           height: UIScreen.main.bounds.size.height))        previewView.contentMode = UIView.ContentMode.scaleAspectFit        view.addSubview(previewView)        //Add a view on top of the cameras' view        boxView = UIView(frame: self.view.frame)        myButton.frame = CGRect(x: 0, y: 0, width: 200, height: 40)        myButton.backgroundColor = UIColor.red        myButton.layer.masksToBounds = true        myButton.setTitle("press me", for: .normal)        myButton.setTitleColor(UIColor.white, for: .normal)        myButton.layer.cornerRadius = 20.0        myButton.layer.position = CGPoint(x: self.view.frame.width/2, y:200)        myButton.addTarget(self, action: #selector(self.onClickMyButton(sender:)), for: .touchUpInside)        view.addSubview(boxView)        view.addSubview(myButton)        self.setupAVCapture()    }    override var shouldAutorotate: Bool {        if (UIDevice.current.orientation == UIDeviceOrientation.landscapeLeft ||        UIDevice.current.orientation == UIDeviceOrientation.landscapeRight ||        UIDevice.current.orientation == UIDeviceOrientation.unknown) {            return false        }        else {            return true        }    }    @objc func onClickMyButton(sender: UIButton){        print("button pressed")    }}// AVCaptureVideoDataOutputSampleBufferDelegate protocol and related methodsextension ViewController:  AVCaptureVideoDataOutputSampleBufferDelegate{     func setupAVCapture(){        session.sessionPreset = AVCaptureSession.Preset.vga640x480        guard let device = AVCaptureDevice        .default(AVCaptureDevice.DeviceType.builtInWideAngleCamera,                  for: .video,                 position: AVCaptureDevice.Position.back) else {                            return        }        captureDevice = device        beginSession()    }    func beginSession(){        var deviceInput: AVCaptureDeviceInput!        do {            deviceInput = try AVCaptureDeviceInput(device: captureDevice)            guard deviceInput != nil else {                print("error: cant get deviceInput")                return            }            if self.session.canAddInput(deviceInput){                self.session.addInput(deviceInput)            }            videoDataOutput = AVCaptureVideoDataOutput()            videoDataOutput.alwaysDiscardsLateVideoFrames=true            videoDataOutputQueue = DispatchQueue(label: "VideoDataOutputQueue")            videoDataOutput.setSampleBufferDelegate(self, queue:self.videoDataOutputQueue)            if session.canAddOutput(self.videoDataOutput){                session.addOutput(self.videoDataOutput)            }            videoDataOutput.connection(with: .video)?.isEnabled = true            previewLayer = AVCaptureVideoPreviewLayer(session: self.session)            previewLayer.videoGravity = AVLayerVideoGravity.resizeAspect            let rootLayer :CALayer = self.previewView.layer            rootLayer.masksToBounds=true            previewLayer.frame = rootLayer.bounds            rootLayer.addSublayer(self.previewLayer)            session.startRunning()        } catch let error as NSError {            deviceInput = nil            print("error: \(error.localizedDescription)")        }    }    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {        // do stuff here    }    // clean up AVCapture    func stopCamera(){        session.stopRunning()    }}

Here i use a UIView called previewView to start the camera and then i add a new UIView called boxView wich is above previewView. I add a UIButton to boxView

IMPORTANT

Remember that in iOS 10 and later you need to first ask the user for permission in order to have access to the camera. You do this by adding a usage key to your app’s Info.plist together with a purpose string because if you fail to declare the usage, your app will crash when it first makes the access.

Here's a screenshot to show the Camera access request

Swift 4

Condensed version of mauricioconde's solution

You can use this as a drop in component:

////  CameraView.swiftimport Foundationimport AVFoundationimport UIKitfinal class CameraView: UIView {    private lazy var videoDataOutput: AVCaptureVideoDataOutput = {        let v = AVCaptureVideoDataOutput()        v.alwaysDiscardsLateVideoFrames = true        v.setSampleBufferDelegate(self, queue: videoDataOutputQueue)        v.connection(with: .video)?.isEnabled = true        return v    }()    private let videoDataOutputQueue: DispatchQueue = DispatchQueue(label: "JKVideoDataOutputQueue")    private lazy var previewLayer: AVCaptureVideoPreviewLayer = {        let l = AVCaptureVideoPreviewLayer(session: session)        l.videoGravity = .resizeAspect        return l    }()    private let captureDevice: AVCaptureDevice? = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)    private lazy var session: AVCaptureSession = {        let s = AVCaptureSession()        s.sessionPreset = .vga640x480        return s    }()    override init(frame: CGRect) {        super.init(frame: frame)        commonInit()    }    required init?(coder aDecoder: NSCoder) {        super.init(coder: aDecoder)        commonInit()    }    private func commonInit() {        contentMode = .scaleAspectFit        beginSession()    }    private func beginSession() {        do {            guard let captureDevice = captureDevice else {                fatalError("Camera doesn't work on the simulator! You have to test this on an actual device!")            }            let deviceInput = try AVCaptureDeviceInput(device: captureDevice)            if session.canAddInput(deviceInput) {                session.addInput(deviceInput)            }            if session.canAddOutput(videoDataOutput) {                session.addOutput(videoDataOutput)            }            layer.masksToBounds = true            layer.addSublayer(previewLayer)            previewLayer.frame = bounds            session.startRunning()        } catch let error {            debugPrint("\(self.self): \(#function) line: \(#line).  \(error.localizedDescription)")        }    }    override func layoutSubviews() {        super.layoutSubviews()        previewLayer.frame = bounds    }}extension CameraView: AVCaptureVideoDataOutputSampleBufferDelegate {}

Swift 3:

@IBOutlet weak var cameraContainerView:UIView!var imagePickers:UIImagePickerController?

On ViewDidLoad:

override func viewDidLoad() {        super.viewDidLoad()        addImagePickerToContainerView()    }

Add Camera Preview to the container view:

func addImagePickerToContainerView(){        imagePickers = UIImagePickerController()        if UIImagePickerController.isCameraDeviceAvailable( UIImagePickerControllerCameraDevice.front) {            imagePickers?.delegate = self            imagePickers?.sourceType = UIImagePickerControllerSourceType.camera            //add as a childviewcontroller            addChildViewController(imagePickers!)            // Add the child's View as a subview            self.cameraContainerView.addSubview((imagePickers?.view)!)            imagePickers?.view.frame = cameraContainerView.bounds            imagePickers?.allowsEditing = false            imagePickers?.showsCameraControls = false            imagePickers?.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]        }    }

On custom button action:

@IBAction func cameraButtonPressed(_ sender: Any) {         if UIImagePickerController.isSourceTypeAvailable(.camera){            imagePickers?.takePicture()         } else{          //Camera not available.        }      }