ios - Swift AVCaptureSession关闭打开按钮错误: Multiple audio/video AVCaptureInputs are not currently supported

Question

我有一个有效的条形码扫描器代码。当我单击 openCamera 按钮时，第一次一切正常。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 fatal error 。代码和错误如下。事实上，是否可以一键切换相机 View ？

// 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() 方法在每次调用时添加一个新输入(使用 self.captureSession.addInput(deviceInput))。

但错误消息明确指出“当前不支持多个音频/视频 AVCaptureInputs”。

因此您一次只能使用一个输入:不要像您那样将它们堆叠在 self.captureSession 中。

例如，您可以在添加新的之前删除前一个(使用 removeInput)。

要确保在添加新输入之前删除所有输入，您可以:

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:不是删除输入，而是更改您的代码以便您添加设备输入仅一次，而不是每次调用该方法时:

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

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

我刚刚在 Playground 中尝试过，它成功了。既然您已经理解了想法，那么您有责任通过调整我的解决方案使其在您自己的应用程序中运行，我无法为您完成，即使我想...;)