iOS fullscreen camera preview without UI

README.md

iOS Fullscreen UI-less camera preview

I recently had a need for an app that displayed a fullscreen camera preview on an iPhone without any UI whatsoever. This is the result of 30 minutes of cobbling together various SO answers, blog posts etc.

All you need to do to use this is:

• Create a new "Single view" poject
• Add a new UIView to the ViewController in the Storyboard
• Connect the outlet previewView to the UIView
• Add the entries below to Info.plist

    <key>NSMicrophoneUsageDescription</key>
    <string>This app does not require access to the microphone.</string>
    <key>NSCameraUsageDescription</key>
    <string>This app requires access to the camera.</string>

ViewController.swift

//
//  ViewController.swift
//  nouicam
//
//  Created by Ulrich Petri on 27.04.2017.
//  Copyright © 2017 Ulrich Petri.
//  
//  License: MIT
//

import UIKit
import AVFoundation

extension AVCaptureVideoOrientation {
    var uiInterfaceOrientation: UIInterfaceOrientation {
        get {
            switch self {
            case .landscapeLeft:        return .landscapeLeft
            case .landscapeRight:       return .landscapeRight
            case .portrait:             return .portrait
            case .portraitUpsideDown:   return .portraitUpsideDown
            }
        }
    }
    
    init(ui:UIInterfaceOrientation) {
        switch ui {
        case .landscapeRight:       self = .landscapeRight
        case .landscapeLeft:        self = .landscapeLeft
        case .portrait:             self = .portrait
        case .portraitUpsideDown:   self = .portraitUpsideDown
        default:                    self = .portrait
        }
    }
    
    init?(orientation:UIDeviceOrientation) {
        switch orientation {
        case .landscapeRight:       self = .landscapeLeft
        case .landscapeLeft:        self = .landscapeRight
        case .portrait:             self = .portrait
        case .portraitUpsideDown:   self = .portraitUpsideDown
        default:
            return nil
        }
    }
}

class ViewController: UIViewController {
    @IBOutlet weak var previewView: UIView!
    var session: AVCaptureSession?
    var videoPreviewLayer: AVCaptureVideoPreviewLayer?
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        session = AVCaptureSession()
        session!.sessionPreset = AVCaptureSessionPreset1920x1080
        let backCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        var error: NSError?
        var input: AVCaptureDeviceInput!
        do {
            input = try AVCaptureDeviceInput(device: backCamera)
        } catch let error1 as NSError {
            error = error1
            input = nil
            print(error!.localizedDescription)
        }
        if error == nil && session!.canAddInput(input) {
            session!.addInput(input)
        }
        let videoOutput = AVCaptureVideoDataOutput()
        if session!.canAddOutput(videoOutput) {
            session!.addOutput(videoOutput)
        }
        videoPreviewLayer = AVCaptureVideoPreviewLayer(session: session)
        videoPreviewLayer!.videoGravity = AVLayerVideoGravityResizeAspect
        videoPreviewLayer!.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
        previewView.layer.addSublayer(videoPreviewLayer!)
        session!.startRunning()
    }
    
    override func didRotate(from fromInterfaceOrientation: UIInterfaceOrientation) {
        videoPreviewLayer!.frame = previewView.bounds
    }
    
    override func willRotate(to toInterfaceOrientation: UIInterfaceOrientation, duration: TimeInterval) {
        videoPreviewLayer!.connection?.videoOrientation = AVCaptureVideoOrientation(ui: toInterfaceOrientation)
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        videoPreviewLayer!.frame = previewView.bounds
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        UIApplication.shared.isIdleTimerDisabled = true
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    override var prefersStatusBarHidden: Bool {
        return true
    }
}