Swift 4相机视图，为什么这会在iPad而不是iPhone上崩溃? [英] Swift 4 camera view, why does this crash on iPad and not on iPhone?

问题描述

我正在为iPad拍照.为什么此代码在iPad上崩溃但在iPhone上仍然可以正常工作?我假设它与设备功能有关?我使用的是运行iOS 12.1和Swift 4.1和Xcode 10的iPad Pro 12.9，已在info.plist中添加了有关相机隐私和照片隐私的必填行.感谢您的指导.

I'm building an app for iPad that takes pictures. Why does this code crash on iPad but yet works fine on iPhone? I'm assuming it has something to do with device capabilities? I'm using an iPad Pro 12.9 running iOS 12.1 and Swift 4.1 with Xcode 10. I have added the required lines in the info.plist about camera privacy and photos privacy. Thanks for your guidance.

它在guard语句所在的行崩溃.

It crashes at the line with the guard statement.

 private func configure() {
    // Preset the session for taking photo in full resolution
    captureSession.sessionPreset = AVCaptureSession.Preset.photo

    // Get the front and back-facing camera for taking photos
    let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInDualCamera], mediaType: AVMediaType.video, position: .unspecified)

    for device in deviceDiscoverySession.devices {
        if device.position == .back {
            backFacingCamera = device
        } else if device.position == .front {
            frontFacingCamera = device
        }
    }

    currentDevice = backFacingCamera

    guard let captureDeviceInput = try? AVCaptureDeviceInput(device: currentDevice) else {
        return
    }

    // Configure the session with the output for capturing still images
    stillImageOutput = AVCapturePhotoOutput()

    // Configure the session with the input and the output devices
    captureSession.addInput(captureDeviceInput)
    captureSession.addOutput(stillImageOutput)

    // Provide a camera preview
    cameraPreviewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    view.layer.addSublayer(cameraPreviewLayer!)
    cameraPreviewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
    cameraPreviewLayer?.frame = view.layer.frame

    // Bring the camera button to front
    view.bringSubviewToFront(cameraButton)
    captureSession.startRunning()

    // Toggle Camera recognizer
    toggleCameraGestureRecognizer.direction = .up
    toggleCameraGestureRecognizer.addTarget(self, action: #selector(toggleCamera))
    view.addGestureRecognizer(toggleCameraGestureRecognizer)

    // Zoom In recognizer
    zoomInGestureRecognizer.direction = .right
    zoomInGestureRecognizer.addTarget(self, action: #selector(zoomIn))
    view.addGestureRecognizer(zoomInGestureRecognizer)

    // Zoom Out recognizer
    zoomOutGestureRecognizer.direction = .left
    zoomOutGestureRecognizer.addTarget(self, action: #selector(zoomOut))
    view.addGestureRecognizer(zoomOutGestureRecognizer)
}

@objc func toggleCamera() {
    captureSession.beginConfiguration()

    // Change the device based on the current camera
    guard let newDevice = (currentDevice?.position == AVCaptureDevice.Position.back) ? frontFacingCamera : backFacingCamera else {
        return
    }

    // Remove all inputs from the session
    for input in captureSession.inputs {
        captureSession.removeInput(input as! AVCaptureDeviceInput)
    }

    // Change to the new input
    let cameraInput:AVCaptureDeviceInput
    do {
        cameraInput = try AVCaptureDeviceInput(device: newDevice)
    } catch {
        print(error)
        return
    }

    if captureSession.canAddInput(cameraInput) {
        captureSession.addInput(cameraInput)
    }

    currentDevice = newDevice
    captureSession.commitConfiguration()
}

推荐答案

这是设备功能. iPad具有广角摄像头.

It's device capabilities. iPads have wide-angle camera.

 let deviceDiscoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera], mediaType: AVMediaType.video, position: .unspecified)

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