如何获取导航栏以在AVCapture会话中显示

Question

I have a navigation bar with a cancel button in the top left that brings the user back to the previous view.

When the AVCapture view comes up, I can not see the bar, the view is fullscreen for the camera view. However, If I tap where the cancel button would be... it works fine.

Why can't I see the navigation bar?

override func viewDidLoad() {
        super.viewDidLoad()

        view.backgroundColor = UIColor.blackColor()
        captureSession = AVCaptureSession()

        let videoCaptureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
        let videoInput: AVCaptureDeviceInput

        do {
            videoInput = try AVCaptureDeviceInput(device: videoCaptureDevice)
        } catch {
            return
        }

        if (captureSession.canAddInput(videoInput)) {
            captureSession.addInput(videoInput)
        } else {
            failed();
            return;
        }
        let metadataOutput = AVCaptureMetadataOutput()

        if (captureSession.canAddOutput(metadataOutput)) {
            captureSession.addOutput(metadataOutput)

            //All of the Supported Barcode Types
            metadataOutput.setMetadataObjectsDelegate(self, queue: dispatch_get_main_queue())
            metadataOutput.metadataObjectTypes = [AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypePDF417Code, AVMetadataObjectTypeUPCECode, AVMetadataObjectTypeCode39Code, AVMetadataObjectTypeCode39Mod43Code, AVMetadataObjectTypeCode93Code, AVMetadataObjectTypeEAN13Code, AVMetadataObjectTypeEAN8Code, AVMetadataObjectTypeCode128Code, AVMetadataObjectTypePDF417Code, AVMetadataObjectTypeQRCode, AVMetadataObjectTypeAztecCode]
        } else {
            failed()
            return
        }
        previewLayer = AVCaptureVideoPreviewLayer(session: captureSession);
        previewLayer.frame = view.layer.bounds;
        previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
        view.layer.addSublayer(previewLayer);

        captureSession.startRunning();
    }

Answer 1

Are you using a UINavigationController as parent of your view controller?

If not, I suspect that your preview, with same size as your view, is added on top of other sub views in your controller, effectively covering them. If this is the case, you can tweak the height of your preview layer to account for the navigation bar height.