Question

我正在尝试显示相机视图，正如您在下面的代码中所看到的，我将其设置为显示任何错误并且如果发生任何错误则不会中断程序，但是当我运行此代码时不会发生错误或显示摄像机视图。我在实际的手机上运行它，手机确实要求它是否有权使用相机。以下是代码

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)

    captureSession = AVCaptureSession()
    captureSession?.sessionPreset = AVCaptureSessionPreset1920x1080

    let backCamera = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
    var input : AVCaptureDeviceInput?
    let error : NSError?
    do {
        input = try AVCaptureDeviceInput(device: backCamera)
    } catch let error as NSError? {
        print(error)



        if error == nil && (captureSession?.canAddInput(input))!{
            captureSession?.addInput(input)

            videoOutput = AVCaptureVideoDataOutput()
            //videoOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecKey]

                if ((captureSession?.canAddOutput(videoOutput)) != nil){
                    captureSession?.addOutput(videoOutput)

                    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
                    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
                    previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
                    cameraView.layer.addSublayer(previewLayer!)
                    captureSession?.startRunning()
            }
        }
    }

}

Answer 1

只有在发生错误时才执行catch的主体。因此，由于您的代码位于catch块内，因此它不会执行，因为它没有发现任何错误。因此，请从catch块中删除代码，并按照@penatheboss的建议将其放在外面。

Answer 2

不要将代码放在catch中。那就是出现问题。

do {
    input = try AVCaptureDeviceInput(device: backCamera)
} catch let error as NSError? {
    print(error)
    return//Stop rest of code
}
if (captureSession?.canAddInput(input))!{
        captureSession?.addInput(input)

        videoOutput = AVCaptureVideoDataOutput()
        //videoOutput?.outputSettings = [AVVideoCodecKey : AVVideoCodecKey]

            if ((captureSession?.canAddOutput(videoOutput)) != nil){
                captureSession?.addOutput(videoOutput)

                previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
                previewLayer?.videoGravity = AVLayerVideoGravityResizeAspect
                previewLayer?.connection.videoOrientation = AVCaptureVideoOrientation.Portrait
                cameraView.layer.addSublayer(previewLayer!)
                captureSession?.startRunning()
        }
    }

没有打印错误，但功能无法运行

2 个答案: