Fix the issue that "viewWillAppear" not called when PhotoVC dissmissed.

[charlietsao]

Ref : https://stackoverflow.com/a/60295024/2151275

Need to set the modalPresentationStyle of PhotoVC to full screen.

Full code of ViewController.swift

import UIKit
import AVFoundation

class ViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {
    
    let captureSession = AVCaptureSession()
    var previewLayer:CALayer!
    var captrueDevice:AVCaptureDevice!
    
    var takePhoto = false

    override func viewDidLoad() {
        super.viewDidLoad()
        prepareCamera()
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        self.captureSession.startRunning()
    }

    func prepareCamera() {
        captureSession.sessionPreset = AVCaptureSession.Preset.photo
        
        let availableDeviceSession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: .video, position: .back)
        
        captrueDevice = availableDeviceSession.devices.first
        beginSession()
    }
    
    func beginSession() {
        do {
            let captureDeviceInput = try AVCaptureDeviceInput(device: captrueDevice)
            captureSession.addInput(captureDeviceInput)
        } catch {
            print(error.localizedDescription)
        }
        
        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        self.previewLayer = previewLayer
        self.view.layer.addSublayer(self.previewLayer)
        self.previewLayer.frame = self.view.layer.frame
        captureSession.startRunning()
        
        let dataOutput = AVCaptureVideoDataOutput()
        dataOutput.videoSettings = [(kCVPixelBufferPixelFormatTypeKey as String): NSNumber(value: kCVPixelFormatType_32BGRA)]
        captureSession.addOutput(dataOutput)
        
        captureSession.commitConfiguration()
        
        
        let queue = DispatchQueue(label: "com.czk.captureQueue")
        dataOutput.setSampleBufferDelegate(self, queue: queue)

        
    }
    
    @IBAction func takePhoto(_ sender: Any) {
        takePhoto = true
    }
    
    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        if takePhoto {
            takePhoto = false
            if let image = getImageFromSampleBuffer(buffer: sampleBuffer) {
                
                
                
                DispatchQueue.main.async {
                    let photoVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "PhotoVC") as! PhotoViewController
                    photoVC.takenPhoto = image
                    photoVC.modalPresentationStyle = .fullScreen
                    self.present(photoVC, animated: true, completion: {
                        self.captureSession.stopRunning()
                    })
                    
                }
            }
        }
    }
    
    func getImageFromSampleBuffer(buffer:CMSampleBuffer) -> UIImage? {
        if let pixelBuffer = CMSampleBufferGetImageBuffer(buffer) {
            let ciImage = CIImage(cvPixelBuffer: pixelBuffer)
            
            let context = CIContext()
            let imageRect = CGRect(x: 0, y: 0, width: CVPixelBufferGetWidth(pixelBuffer), height: CVPixelBufferGetHeight(pixelBuffer))
            
            if let image = context.createCGImage(ciImage, from: imageRect) {
                return UIImage(cgImage: image, scale: UIScreen.main.scale, orientation: .right)
            }
        }
        
        return nil
    }

}