AVCapture會話捕獲圖像SWIFT

Question

我創建了一個AVCaptureSession來捕獲視頻輸出並通過UIView將其顯示給用戶。 現在我希望能夠單擊按鈕（takePhoto方法）並在UIImageView中顯示會話中的圖像。 我試圖迭代每個設備連接並嘗試保存輸出但是沒有用。 我的代碼如下

let captureSession = AVCaptureSession()
var stillImageOutput: AVCaptureStillImageOutput!

@IBOutlet var imageView: UIImageView!
@IBOutlet var cameraView: UIView!


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

override func viewDidLoad() {
    // Do any additional setup after loading the view, typically from a nib.
    super.viewDidLoad()
    println("I AM AT THE CAMERA")
    captureSession.sessionPreset = AVCaptureSessionPresetLow
    self.captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    if(captureDevice != nil){
        beginSession()
    }
}
    func beginSession() {

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

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

    var previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
    self.cameraView.layer.addSublayer(previewLayer)
    previewLayer?.frame = self.cameraView.layer.frame
    captureSession.startRunning()
}

@IBAction func takePhoto(sender: UIButton) {
    self.stillImageOutput.captureStillImageAsynchronouslyFromConnection(self.stillImageOutput.connectionWithMediaType(AVMediaTypeVideo)) { (buffer:CMSampleBuffer!, error:NSError!) -> Void in
        var image = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(buffer)
        var data_image = UIImage(data: image)
        self.imageView.image = data_image
    }
}
}

Answer 1

在啟動之前向會話添加輸入和輸出時，應嘗試添加新線程。 在Apple的文檔中，他們說

重要提示：startRunning方法是一個阻塞調用，可能需要一些時間，因此您應該在串行隊列上執行會話設置，以便不阻止主隊列（這使UI保持響應）。 有關規范實現示例，請參閱AVCam for iOS。

嘗試在create session方法中使用調度，如下所示

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), { // 1
        self.captureSession.addOutput(self.stillImageOutput)
        self.captureSession.addInput(AVCaptureDeviceInput(device: self.captureDevice, error: &err))
        self.captureSession.sessionPreset = AVCaptureSessionPresetPhoto
        if err != nil {
            println("error: \(err?.localizedDescription)")
        }
        var previewLayer = AVCaptureVideoPreviewLayer(session: self.captureSession)
        previewLayer?.frame = self.cameraView.layer.bounds
        previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
        dispatch_async(dispatch_get_main_queue(), { // 2
                    // 3
            self.cameraView.layer.addSublayer(previewLayer)
            self.captureSession.startRunning()
            });
        });