iPad的Swift Playground相机访问

Question

在iPad的Swift Playground应用程序的最新更新说明中，我看到相机可以通过playgrounds访问。为了测试目的，我因此创建了一个playground来访问我的iPad后置摄像头。我使用了以下参考资料：

• https://github.com/codepath/ios_guides/wiki/Creating-a-Custom-Camera-View
• https://github.com/francip/swift-playground-camera/blob/master/Camera.playground/Contents.swift

这是我的代码：

import UIKit
import AVFoundation
import PlaygroundSupport

class MainViewController : UIViewController {
    private var _session: AVCaptureSession?
    private var _captureInput: AVCaptureInput?
    private var _stillImageOutput: AVCaptureStillImageOutput?
    private var _frontCamera: AVCaptureDevice?
    private var _previewView: UIView?
    private var _previewLayer: AVCaptureVideoPreviewLayer?

public override func loadView() {
    print("loadView()")

    _previewView = UIView()
    guard let view = _previewView else {
        printError(errMsg: "View could not be created!")
        return
    }
    view.backgroundColor = UIColor.brown
    self.view = view
}

public override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    // Create a capture session
    _session = AVCaptureSession()
    guard let session = _session  else {
        printError(errMsg: "Session is empty!")
        return
    }
    session.beginConfiguration()
    session.sessionPreset = AVCaptureSession.Preset.photo

    // Get access to front camera
    _frontCamera = AVCaptureDevice.default(for: AVMediaType.video)

    guard let frontCamera = _frontCamera
        else {
            printError(errMsg: "Front camera not accessible!")
            return
    }

    do{
        _captureInput = try AVCaptureDeviceInput(device: frontCamera)
    } catch let err as NSError {
        printError(errMsg: err.localizedDescription)
        return
    }

    // Add input to session
    guard let captureInput = _captureInput else {
        printError(errMsg: "Capture input not available!")
        return
    }

    if session.canAddInput(captureInput){
        session.addInput(captureInput)
    }

    // Configurw the image output
    _stillImageOutput = AVCaptureStillImageOutput()
    guard let sillImageOutput = _stillImageOutput else {
        printError(errMsg: "Image output not available!")
        return
    }

    sillImageOutput.outputSettings = [AVVideoCodecKey: AVVideoCodecJPEG]

    if session.canAddOutput(sillImageOutput) {
        session.addOutput(sillImageOutput)
    }
    session.commitConfiguration()
    // Add video preview layer
    _previewLayer = AVCaptureVideoPreviewLayer(session: session)

    guard let previewLayer = _previewLayer else {
        printError(errMsg: "Preview layer not available!")
        return
    }

    previewLayer.videoGravity = AVLayerVideoGravity.resizeAspect
    previewLayer.connection?.videoOrientation = AVCaptureVideoOrientation.portrait
    guard let view = _previewView else {
        printError(errMsg: "View not available!")
        return
    }
    view.layer.addSublayer(previewLayer)
    view.layer.borderWidth = 5

    // Start the capture session
    session.startRunning()
}

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

public override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    guard let previewLayer = _previewLayer else {
        printError(errMsg: "Preview layer not available!")
        return
    }
    guard let previewView = _previewView else {
        printError(errMsg: "View not available!")
        return
    }
    print(previewView.bounds)
    previewLayer.frame = previewView.bounds
}

private func printError(errMsg: String) {
    print("[Error]: " + errMsg)
}
}

PlaygroundPage.current.liveView = MainViewController()

请忽略会话等私有变量，我知道我可以/应该将它们设为方法本地变量。

我只看到视图的棕色背景。 第一次运行应用程序时，iOS 询问我是否允许Playgrounds应用程序访问相机，我同意了。在设置中，我也可以看到该应用程序已经获得了相机权限。

iOS版本：10.3.3 Playground应用程序：1.6.1

- Fabian

---

你需要将视图的 bounds 分配为 previewLayer 的框架。我认为当前的 previewLayer.frame 是 CGRect.zero。 - Tarun Tyagi

Answer 1

看起来这仅适用于iOS 11。 我在运行iOS 10.3的iPad上检查了您的代码，视频预览为空。 在另一台运行iOS 11的平板电脑上，相同的代码可以正常运行。

- Kamil Szostakowski