Question

我想在Swift Playgrounds iPad应用程序上访问iPad的相机。我发现捕捉视频数据是不可能的，即使我的游乐场运行正常。

captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!)是AVCaptureVideoDataOutputSampleBufferDelegate协议的委托方法，未被调用（可能是因为没有视频数据进入），而是在我的iOS应用程序中。

我的操场上的视图应该显示FaceTime摄像机视图。为什么即使Apple explicitly says it's allowed to do so也无法显示相机输出？此外，Playground应用程序会在我打开游乐场时立即询问相机权限，因此应该以某种方式允许它。

import UIKit
import CoreImage
import AVFoundation
import ImageIO
import PlaygroundSupport

class Visage: NSObject, AVCaptureVideoDataOutputSampleBufferDelegate {

    var visageCameraView : UIView = UIView()
    fileprivate var faceDetector : CIDetector?
    fileprivate var videoDataOutput : AVCaptureVideoDataOutput?
    fileprivate var videoDataOutputQueue : DispatchQueue?
    fileprivate var cameraPreviewLayer : AVCaptureVideoPreviewLayer?
    fileprivate var captureSession : AVCaptureSession = AVCaptureSession()
    fileprivate let notificationCenter : NotificationCenter = NotificationCenter.default

    override init() {
        super.init()

        self.captureSetup(AVCaptureDevicePosition.front)
        var faceDetectorOptions : [String : AnyObject]?
        faceDetectorOptions = [CIDetectorAccuracy : CIDetectorAccuracyHigh as AnyObject]
        self.faceDetector = CIDetector(ofType: CIDetectorTypeFace, context: nil, options: faceDetectorOptions)
    }

    func beginFaceDetection() {
        self.captureSession.startRunning()
    }

    func endFaceDetection() {
        self.captureSession.stopRunning()
    }

    fileprivate func captureSetup (_ position : AVCaptureDevicePosition) {
        var captureError : NSError?
        var captureDevice : AVCaptureDevice!

        for testedDevice in AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo){
            if ((testedDevice as AnyObject).position == position) {
                captureDevice = testedDevice as! AVCaptureDevice
            }
        }

        if (captureDevice == nil) {
            captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
        }

        var deviceInput : AVCaptureDeviceInput?
        do {
            deviceInput = try AVCaptureDeviceInput(device: captureDevice)
        } catch let error as NSError {
            captureError = error
            deviceInput = nil
        }
        captureSession.sessionPreset = AVCaptureSessionPresetHigh

        if (captureError == nil) {
            if (captureSession.canAddInput(deviceInput)) {
                captureSession.addInput(deviceInput)
            }

            self.videoDataOutput = AVCaptureVideoDataOutput()
            self.videoDataOutput!.videoSettings = [kCVPixelBufferPixelFormatTypeKey as AnyHashable: Int(kCVPixelFormatType_32BGRA)]
            self.videoDataOutput!.alwaysDiscardsLateVideoFrames = true
            self.videoDataOutputQueue = DispatchQueue(label: "VideoDataOutputQueue", attributes: [])
            self.videoDataOutput!.setSampleBufferDelegate(self, queue: self.videoDataOutputQueue!)

            if (captureSession.canAddOutput(self.videoDataOutput)) {
                captureSession.addOutput(self.videoDataOutput)
            }
        }

        visageCameraView.frame = UIScreen.main.bounds
        let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        previewLayer?.frame = UIScreen.main.bounds
        previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        visageCameraView.layer.addSublayer(previewLayer!)
    }

    // NOT CALLED
    func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {            
        print("delegate method called!")
    }
}

class SmileView: UIView {
    let smileView = UIView()
    var smileRec: Visage!

    override init(frame: CGRect) {
        super.init(frame: frame)
        self.addSubview(smileView)
        self.translatesAutoresizingMaskIntoConstraints = false
        smileRec = Visage()
        smileRec.beginFaceDetection()
        let cameraView = smileRec.visageCameraView
        self.addSubview(cameraView)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

let frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height)
let sView = SmileView(frame: frame)
PlaygroundPage.current.liveView = sView

Answer 1

编辑：这应该已经修复：）

-

编辑：这被证实是Apple的一个错误。

我已提交错误报告，当有新的官方信息出现时我会更新此答案。

Answer 2

我认为您需要设置needsIndefiniteExecution属性，以便在代码完成后不会停止执行。来自苹果：

默认情况下，执行所有顶级代码，然后执行   终止。使用异步代码时，启用无限期   执行以允许执行在结束后继续   达到了playground的顶级代码。反过来，这给了线程   和回调时间执行。

编辑游乐场会自动停止执行，即使是   启用了无限期执行。

将needsIndefiniteExecution设置为true以在之后继续执行   顶级代码的结尾。将其设置为false以停止执行该操作   点。

最后可能的代码是：

let frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: UIScreen.main.bounds.height)
let sView = SmileView(frame: frame)
PlaygroundPage.current.needsIndefiniteExecution = true
PlaygroundPage.current.liveView = sView

无法在Swift Playgrounds上捕获视频数据，captureOutput AVCaptureVideoDataOutputSampleBufferDelegate委托方法未调用

2 个答案: