Swift - OS X 上的 AVFoundation 添加子层问题答案

【问题标题】：Swift - AVFoundation on OS X adding sublayer issueSwift - OS X 上的 AVFoundation 添加子层问题
【发布时间】：2015-06-09 22:47:03
【问题描述】：

我正在尝试在自定义视图中预览我的视频设备。但我得到的只是一个空窗。我发现访问我的相机没有问题。应用程序启动后，我看到我的罗技相机 LED 指示灯亮起。我假设我的问题是将预览层添加为子层。

这是我的简单代码：

import Cocoa
import AVFoundation

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

@IBOutlet weak var video: NSView!
@IBOutlet weak var window: NSWindow!

let captureSession = AVCaptureSession()
var captureDevice : AVCaptureDevice?
var previewLayer : AVCaptureVideoPreviewLayer?

func applicationDidFinishLaunching(aNotification: NSNotification) {

    captureSession.sessionPreset = AVCaptureSessionPresetLow
    let devices = AVCaptureDevice.devices()
    for device in devices {

        if (device.hasMediaType(AVMediaTypeVideo)) {
            captureDevice = device as? AVCaptureDevice
            println(captureDevice)
        }
    }

    if captureDevice != nil {
        beginSession()
    }


}

func beginSession() {

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

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



    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer!.frame = self.video.bounds
    previewLayer!.videoGravity = AVLayerVideoGravityResizeAspectFill
    self.video.layer?.addSublayer(previewLayer)
    captureSession.startRunning()
}

func applicationWillTerminate(aNotification: NSNotification) {
    // Insert code here to tear down your application
}


}

【问题讨论】：

标签： macos swift avfoundation nsview

【解决方案1】：

在 Swift 2 中，错误处理发生了变化。如果您使用 Main.storyboard，则以下方法应该有效：

class ViewController: NSViewController {

let captureSession = AVCaptureSession()
var captureDevice: AVCaptureDevice?
var previewLayer: AVCaptureVideoPreviewLayer?
var previewPanel: NSView!

override func viewDidLoad() {
    super.viewDidLoad()
    captureSession.sessionPreset = AVCaptureSessionPresetLow
    let devices = AVCaptureDevice.devices()
    for device in devices {
        if (device.hasMediaType(AVMediaTypeVideo)) {
            captureDevice = device as? AVCaptureDevice
            //Swift.print("device: \(captureDevice)")
        }
    }
    Swift.print("beginning")
    do {
        let deviceInput = try AVCaptureDeviceInput(device: captureDevice)
        captureSession.addInput(deviceInput)
        // get the CustomView as preview panel
        previewPanel = self.view.subviews.first
        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
        previewLayer!.frame = self.view.bounds
        // add layer to preview
        previewLayer!.videoGravity = AVLayerVideoGravityResizeAspectFill
        previewPanel.layer?.addSublayer(previewLayer!)
        captureSession.startRunning()
    } catch let error as NSError {
        Swift.print("Error: no valid camera input in \(error.domain)")
    }
}
override var representedObject: AnyObject? {
    didSet {
        // Update the view, if already loaded.
    }
}

别忘了添加 CustomView。

【讨论】：

【解决方案2】：

解决了。在 Interface Builder 中，我需要在核心动画中添加自定义视图。

【讨论】：

【解决方案3】：

对于我的小型 swift-base AVFoundation 抓取器，这篇问答文章帮助了我。我注意到以下检查对于界面构建器中的“自定义视图”很重要：

属性检查器>勾选“可以同时绘制”：
View Effects Inspector > 在“核心动画层列表”中检查您的自定义视图，（甚至可以取消选中主视图控制器）

【讨论】：