如何停止collectionView單元中的相機滯后？

Question

我有一個collectionView，其中的單元格充當屏幕。 打開應用程序后，當我向相機單元滑動時，會出現一秒鍾的延遲，然后在來回滑動的過程很順暢，下面是此延遲的視頻。 是否有任何方法可以防止此操作在到達單元之前在后台啟動捕獲會話？ 謝謝您的幫助。

相機單元代碼

import UIKit
import AVFoundation


class MainCameraCollectionViewCell: UICollectionViewCell {

    var captureSession = AVCaptureSession()
    private var sessionQueue: DispatchQueue!
    var captureConnection = AVCaptureConnection()

    var backCamera: AVCaptureDevice?
    var frontCamera: AVCaptureDevice?
    var currentCamera: AVCaptureDevice?

    var photoOutPut: AVCapturePhotoOutput?

    var cameraPreviewLayer: AVCaptureVideoPreviewLayer?

    var image: UIImage?

    var usingFrontCamera = false

    override func awakeFromNib() {
        super.awakeFromNib()
        setupCaptureSession()
        setupDevice()
        setupInput()
        self.setupPreviewLayer()
        startRunningCaptureSession
    }

    func setupCaptureSession(){
        captureSession.sessionPreset = AVCaptureSession.Preset.photo
        sessionQueue = DispatchQueue(label: "session queue")
    }

    func setupDevice(usingFrontCamera:Bool = false){
        DispatchQueue.main.async {
            //sessionQueue.async {
            let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [AVCaptureDevice.DeviceType.builtInWideAngleCamera], mediaType: AVMediaType.video, position: AVCaptureDevice.Position.unspecified)
            let devices = deviceDiscoverySession.devices

            for device in devices{
                if usingFrontCamera && device.position == AVCaptureDevice.Position.front {
                    //backCamera = device
                    self.currentCamera = device
                } else if device.position == AVCaptureDevice.Position.back {
                    //frontCamera = device
                    self.currentCamera = device
                }
            }
        }
    }
    func setupInput() {
        DispatchQueue.main.async {
            do {
                let captureDeviceInput = try AVCaptureDeviceInput(device: self.currentCamera!)
                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 = AVLayerVideoGravity.resizeAspectFill
        cameraPreviewLayer?.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
        cameraPreviewLayer?.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height)
        self.layer.insertSublayer(cameraPreviewLayer!, at: 0)
    }

    func startRunningCaptureSession(){
        captureSession.startRunning()
    }

    @IBAction func cameraButton_Touched(_ sender: Any) {
        let settings = AVCapturePhotoSettings(format: [AVVideoCodecKey: AVVideoCodecType.jpeg])
        //
        settings.isAutoStillImageStabilizationEnabled = true
        if let photoOutputConnection = self.photoOutPut?.connection(with: .video){
            photoOutputConnection.videoOrientation = (cameraPreviewLayer?.connection?.videoOrientation)!
        }
    }



    @IBAction func Flip_camera(_ sender: UIButton?) {
        print("Flip Touched")

        self.captureSession.beginConfiguration()
         if let inputs = self.captureSession.inputs as? [AVCaptureDeviceInput] {
            for input in inputs {
                self.captureSession.removeInput(input)
                print("input removed")
            }
            //This seemed to have fixed it
            for output in self.captureSession.outputs{
                captureSession.removeOutput(output)
                print("out put removed")
            }
        }


        self.usingFrontCamera = !self.usingFrontCamera
        self.setupCaptureSession()
        self.setupDevice(usingFrontCamera: self.usingFrontCamera)
        self.setupInput()
        self.captureSession.commitConfiguration()
        self.startRunningCaptureSession()
    }

}

Answer 1

初始化相機需要時間。 一旦您的應用請求使用相機，就必須在后台初始化支持軟件，這實際上不可能加快速度。

我建議將與AVFoundation相關的所有內容放在后台線程中，並在應用加載后對其進行初始化。 這樣，一旦用戶准備好滑動到相機單元，便可以為用戶准備好相機。 如果您不想預加載，則至少仍可以將AVFoundation放在后台，並利用某種活動指示器向用戶顯示正在加載某些內容，而不僅僅是在相機啟動時阻止主線程起來。