无法使用 AVCaptureDevice 获取设备

Question

我设法找到了一些代码，可以让我访问手机的设备（例如相机）。问题是当我使用 Xcode 编译代码（并且打印不同的设备）时，我得到一个空数组。

这是我写的：

import UIKit
import AVFoundation

class ViewController: UIViewController {

  let captureSession = AVCaptureSession()
  var previewLayer : AVCaptureVideoPreviewLayer?

  // If we find a device we'll store it here for later us
  var captureDevice : AVCaptureDevice?

  override func viewDidLoad() {
    super.viewDidLoad()            
    // Do any additional setup after loading the view, typically from a nib.

    captureSession.sessionPreset = AVCaptureSessionPresetHigh

    let devices = AVCaptureDevice.devices()
    println(devices)
    // Loop through all the capture devices on this phone
    for (device in devices) {
        // Make sure this particular device supports video
        if (device.hasMediaType(AVMediaTypeVideo)) {
         // Finally check the position and confirm we've got the back camera
            if(device.position == AVCaptureDevicePosition.Back) {
                captureDevice = device as? AVCaptureDevice
                if captureDevice != nil {
                    println("Capture device found")
                    beginSession()
                }
            }
        }
      }

    }

    func beginSession() {

      var err : NSError? = nil
      captureSession.addInput(AVCaptureDeviceInput(device: captureDevice, error: &err))

      if err != nil {
          println("error: \(err?.localizedDescription)")
      }

      previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
      self.view.layer.addSublayer(previewLayer)
      previewLayer?.frame = self.view.layer.frame

      captureSession.startRunning()

    }

  }

你对我为什么得到一个空数组有任何想法吗？

Answer 1

检查 Swift 4 的当前授权状态

 AVCaptureDevice.authorizationStatus(for: AVMediaType.video)

Answer 2

首先查看授权的当前状态

AVCaptureDevice.authorizationStatusForMediaType(AVMediaTypeVideo)

更多细节你可以阅读this article

Answer 3

如果您只在模拟器中运行它，则该数组将始终为空，因为它没有可供选择的物理硬件。事实上，如果你试图访问模拟器内部的物理硬件，它就会崩溃。如果您插入设备但仍然得到一个空数组，请告诉我。