我试图从我的 View Controller 中提取一些代码来清理它，并尽可能将代码保持为 DRY。它在如下情况下工作正常:
class InitialRegistrationViewController: UIViewController, UINavigationControllerDelegate, UIImagePickerControllerDelegate, NVActivityIndicatorViewable {
var session: AVCaptureSession?
var stillImageOutput: AVCaptureStillImageOutput?
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
if Platform.isPhone {
session = AVCaptureSession()
session!.sessionPreset = AVCaptureSessionPresetPhoto
var frontCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
let availableCameraDevices = AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo)
for device in availableCameraDevices as! [AVCaptureDevice] {
if device.position == .front {
frontCamera = device
}
}
var error: NSError?
var input: AVCaptureDeviceInput!
do {
input = try AVCaptureDeviceInput(device: frontCamera)
} catch let error1 as NSError {
error = error1
input = nil
print(error!.localizedDescription)
}
if error == nil && session!.canAddInput(input) {
session!.addInput(input)
stillImageOutput = AVCaptureStillImageOutput()
stillImageOutput?.outputSettings = [AVVideoCodecKey: AVVideoCodecJPEG]
if session!.canAddOutput(stillImageOutput) {
session!.addOutput(stillImageOutput)
session!.startRunning()
}
}
}
}
func capturePhoto() {
if let videoConnection = stillImageOutput!.connection(withMediaType: AVMediaTypeVideo) {
stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler: { (sampleBuffer, error) -> Void in
if sampleBuffer != nil {
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer)
let dataProvider = CGDataProvider(data: imageData as! CFData)
let cgImageRef = CGImage(jpegDataProviderSource: dataProvider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)
let image = UIImage(cgImage: cgImageRef!, scale: 1.0, orientation: UIImageOrientation.right)
self.profileImage.image = image
}
})
}
}
}
但是当我提取到如下助手时:
导入 UIKit 导入 AVFoundation
class ProfilePhoto {
var session: AVCaptureSession?
var stillImageOutput: AVCaptureStillImageOutput?
func startSession() {
if Platform.isPhone {
session = AVCaptureSession()
session!.sessionPreset = AVCaptureSessionPresetPhoto
var frontCamera = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo)
let availableCameraDevices = AVCaptureDevice.devices(withMediaType: AVMediaTypeVideo)
for device in availableCameraDevices as! [AVCaptureDevice] {
if device.position == .front {
frontCamera = device
}
}
var error: NSError?
var input: AVCaptureDeviceInput!
do {
input = try AVCaptureDeviceInput(device: frontCamera)
} catch let error1 as NSError {
error = error1
input = nil
print(error!.localizedDescription)
}
if error == nil && session!.canAddInput(input) {
session!.addInput(input)
stillImageOutput = AVCaptureStillImageOutput()
stillImageOutput?.outputSettings = [AVVideoCodecKey: AVVideoCodecJPEG]
if session!.canAddOutput(stillImageOutput) {
session!.addOutput(stillImageOutput)
session!.startRunning()
}
}
}
}
func capture() -> UIImage {
var image: UIImage!
if let videoConnection = stillImageOutput!.connection(withMediaType: AVMediaTypeVideo) {
stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler: { (sampleBuffer, error) -> Void in
if sampleBuffer != nil {
let cgImageRef = self.setBufferData(sampleBuffer: sampleBuffer!)
image = UIImage(cgImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.right)
}
})
}
return image
}
func setBufferData(sampleBuffer: CMSampleBuffer ) -> CGImage {
let imageData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(sampleBuffer)
let dataProvider = CGDataProvider(data: imageData as! CFData)
let cgImageRef = CGImage(jpegDataProviderSource: dataProvider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)
return cgImageRef!
}
}
我调用 InitialRegistrationViewController 的地方:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
profilePhoto.startSession()
}
func capturePhoto() {
profileImage.image = profilePhoto.capture()
}
在 profilePhoto.capture() 中返回图像时，出现 fatal error :在展开可选值时意外发现 nil。
我不明白 session 是如何工作的，因为我是 ios 的新手，但我认为这是因为当我 try catch 图像时 session 正在结束(？)？任何见解都会很棒。谢谢
更新:我赞成给出的答案，因为它足够接近，下面是对我有用的。
func capture(completion: @escaping (UIImage?) -> Void) {
if let videoConnection = stillImageOutput!.connection(withMediaType: AVMediaTypeVideo) {
stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler: { (sampleBuffer, error) -> Void in
if sampleBuffer != nil {
let cgImageRef = self.setBufferData(sampleBuffer: sampleBuffer!)
let image: UIImage! = UIImage(cgImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.right)
completion(image)
} else {
completion(nil)
}
})
} else {
completion(nil)
}
}
最佳答案
您的 capture() 方法进行异步调用以获取 UIImage，因此当它[立即]返回时，返回的值始终为 nil。
@dan 建议的文章展示了一种回调模式，可用于将图像返回给调用者，请确保在继续之前了解此机制。
func capture(result: (image: UIImage?) -> Void) -> UIImage
{
if let videoConnection = stillImageOutput!.connection(withMediaType: AVMediaTypeVideo)
{
stillImageOutput?.captureStillImageAsynchronously(from: videoConnection, completionHandler:
{ (sampleBuffer, error) -> Void in
if sampleBuffer != nil
{
let cgImageRef = self.setBufferData(sampleBuffer: sampleBuffer!)
var image: UIImage! = UIImage(cgImage: cgImageRef, scale: 1.0, orientation: UIImageOrientation.right)
result(image: image)
}
else
result(image: nil)
})
}
else
result(image: nil)
}
要调用它，您可以使用
capture(){(image: UIImage?) -> Void in
//use the image that was just retrieved
}
您现在已将 capture() 方法设为异步，并通过回调报告其返回值。
关于ios - AvCaptureSession代码提取错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42141112/