Swift AVCaptureSession Close Open Button Error : Multiple audio/video AVCaptureInputs are not currently supported

Question

我有一个可用的条形码扫描器代码。当我单击 openCamera 按钮时，第一次一切都很好。当我单击 closeCamera 按钮时，很好，但是如果我再次单击 openCamera 按钮会出现致命错误。代码和错误如下。事实上，是否可以一键切换相机视图？

// Barcode Camera Properties
let captureSession = AVCaptureSession()
var captureDevice:AVCaptureDevice?
var captureLayer:AVCaptureVideoPreviewLayer?

override func viewDidLoad() {
    super.viewDidLoad()
    self.cameraView.alpha = 0
}

@IBAction func closeCamera(sender: AnyObject) {
    self.captureLayer!.hidden = true
    self.captureSession.stopRunning()
}

@IBAction func openCamera(sender: AnyObject) {
    self.cameraView.alpha = 1
    self.cameraView.animate()
    setupCaptureSession()
}

//MARK: Session Startup
private func setupCaptureSession(){
    self.captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    do {
        let deviceInput = try AVCaptureDeviceInput(device: captureDevice) as AVCaptureDeviceInput
        //Add the input feed to the session and start it
        self.captureSession.addInput(deviceInput)
        self.setupPreviewLayer({
            self.captureSession.startRunning()
            self.addMetaDataCaptureOutToSession()
        })
    } catch let setupError as NSError {
        self.showError(setupError.localizedDescription)
    }
}

private func setupPreviewLayer(completion:() -> ()){
    self.captureLayer = AVCaptureVideoPreviewLayer(session: captureSession) as AVCaptureVideoPreviewLayer
    if let capLayer = self.captureLayer {
        capLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
        capLayer.frame = self.cameraView.frame
        self.view.layer.addSublayer(capLayer)
        completion()
    } else {
        self.showError("An error occured beginning video capture.")
    }
}

//MARK: Metadata capture
func addMetaDataCaptureOutToSession() {
    let metadata = AVCaptureMetadataOutput()
    self.captureSession.addOutput(metadata)
    metadata.metadataObjectTypes = metadata.availableMetadataObjectTypes
    metadata.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
}

//MARK: Delegate Methods
func captureOutput(captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [AnyObject]!, fromConnection connection: AVCaptureConnection!) {
    for metaData in metadataObjects {
        let decodedData:AVMetadataMachineReadableCodeObject = metaData as! AVMetadataMachineReadableCodeObject
        self.pCodeTextField.text = decodedData.stringValue
        //decodedData.type
    }
}

//MARK: Utility Functions
func showError(error:String) {
    let alertController = UIAlertController(title: "Error", message: error, preferredStyle: .Alert)
    let dismiss:UIAlertAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Destructive, handler:{(alert:UIAlertAction) in
        alertController.dismissViewControllerAnimated(true, completion: nil)
    })
    alertController.addAction(dismiss)
    self.presentViewController(alertController, animated: true, completion: nil)
}

错误：

* Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '* Multiple audio/video AVCaptureInputs are not currently supported.'

*** First throw call stack: (0x23f3410b 0x236dae17 0x2946bf73 0x2946b8bf 0x6d0d8 0x6ce28 0x6cebc 0x280a86cd 0x280a8659 0x2809064f 0x280a7fb5 0x28062275 0x280a0e21 0x280a05d3 0x280712f9 0x2806f98b 0x23ef768f 0x23ef727d 0x23ef55eb 0x23e48bf9 0x23e489e5 0x25094ac9 0x280d8ba1 0xa794c 0x23af7873)

libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

Answer 1

您的 setupCaptureSession() 方法 每次调用时都会添加 一个新输入（使用 self.captureSession.addInput(deviceInput)）。

但错误消息明确指出"Multiple audio/video AVCaptureInputs are not currently supported"。

所以您一次只能使用一个输入：不要像您一样将它们堆叠在 self.captureSession 中。

例如，您可以在添加新的之前删除之前的（使用 removeInput）。

要确保在添加新输入之前删除所有输入，您可以这样做：

if let inputs = captureSession.inputs as? [AVCaptureDeviceInput] {
    for input in inputs {
        captureSession.removeInput(input)
    }
}

就在 self.captureSession.addInput(deviceInput).

之前

如果它仍然不起作用...尝试不同的方法：不要删除输入，而是更改代码以便添加设备输入只需一次，而不是每次该方法称为：

if captureSession.inputs.isEmpty {
    self.captureSession.addInput(deviceInput)
}

而不仅仅是 self.captureSession.addInput(deviceInput).

我刚刚在 Playground 上试过了，它成功了。既然你已经理解了 idea，你有责任通过调整我的解决方案使其在你自己的应用程序中工作，我不能为你做，即使我想.. .;)

Swift AVCaptureSession Close Open Button Error : Multiple audio/video AVCaptureInputs are not currently supported

Swift AVCaptureSession Close Open Button Error : Multiple audio/video AVCaptureInputs are not currently supported

ios

swift

avfoundation

avcapturesession