SwiftUI- 服务器未接收到 base64 字符串

Question

我想做的是拍照，将其编码为 base64，然后将其通过字典发送到我的服务器。当我发送字典时，有时它会使用 base64 发送，有时即使我不做任何更改也会在没有它的情况下发送。这是相机视图的代码

struct CameraView: View {

@StateObject var camera = CameraModel()

var body: some View {
    ZStack {
        CameraPreview(camera: camera)
            .ignoresSafeArea(.all, edges: .all)
        
        VStack{
            if camera.isTaken{
                
                HStack {
                    
                    Spacer()
                    
                    Button(action: camera.retake, label: {
                        Image(systemName: "arrow.triangle.2.circlepath.camera")
                            .foregroundColor(.black)
                            .padding()
                            .background(Color.white)
                            .clipShape(Circle())
                    })
                    .padding(.trailing, 10)
                }
            }
    
            Spacer()
            
            HStack{
                if camera.isTaken{
                    Button(action: camera.sendPicData , label: {
                        Text("Save")
                            .foregroundColor(.black)
                            .fontWeight(.semibold)
                            .padding(.vertical, 10)
                            .padding(.horizontal, 10)
                            .background(Color.white)
                            .clipShape(Capsule())
                    })
                    .padding(.leading)
                    
                    Spacer()
                }
                else{
                    Button(action: camera.takePic, label: {
                        ZStack{
                            Circle()
                                .fill(Color.white)
                                .frame(width: 65, height: 65)
                            
                            Circle()
                                .stroke(Color.white, lineWidth: 2)
                                .frame(width: 75, height: 75)
                        }
                    })
                }
            }
            .frame(height: 75)
        }
    }
    .onAppear(perform: {
        camera.Check()
    })
}
}

struct CameraPreview: UIViewRepresentable{

@ObservedObject var camera: CameraModel

func makeUIView(context: Context) -> UIView {
    let view = UIView(frame: UIScreen.main.bounds)
    
    camera.preview = AVCaptureVideoPreviewLayer(session: camera.session)
    camera.preview.frame = view.frame
    
    camera.preview.videoGravity = .resizeAspectFill
    view.layer.addSublayer(camera.preview)
    
    camera.session.startRunning()
    
    return view
    
}

func updateUIView(_ uiView: UIView, context: Context) {
    
}
}

以及拍照并发送到服务器的代码

class CameraModel: NSObject, ObservableObject, AVCapturePhotoCaptureDelegate{
@Published var isTaken = false
@Published var alert = false
@Published var sendPic = false
@Published var session = AVCaptureSession()
@Published var output = AVCapturePhotoOutput()
@Published var preview: AVCaptureVideoPreviewLayer!
@Published var picData = Data(count: 0)

func Check(){
    switch AVCaptureDevice.authorizationStatus(for: .video) {
    case .authorized:
        setUp()
        return
    case .notDetermined:
        AVCaptureDevice.requestAccess(for: .video) { (status) in
            if status{
                self.setUp()
            }
        }
    case .denied:
        self.alert.toggle()
        return
    default:
        return
    }
}

func setUp(){
    do{
        self.session.beginConfiguration()
        
        let device = AVCaptureDevice.default(.builtInWideAngleCamera, for: .video, position: .back)
        let input = try AVCaptureDeviceInput(device: device!)
        
        if self.session.canAddInput(input){
            self.session.addInput(input)
        }
        
        if self.session.canAddOutput(self.output){
            self.session.addOutput(self.output)
        }
        self.session.commitConfiguration()
    }
    catch{
        print(error.localizedDescription)
    }
}

func takePic(){
    DispatchQueue.global(qos: .background).async {
        self.output.capturePhoto(with: AVCapturePhotoSettings(), delegate: self)
        self.session.stopRunning()
        
        DispatchQueue.main.async {
            withAnimation{self.isTaken.toggle()}
        }
        print("pic taken...")
    }
}

func retake(){
    DispatchQueue.global(qos: .background).async {
        self.session.startRunning()
        
        DispatchQueue.main.async {
            withAnimation{self.isTaken.toggle()}
        }
    }
}

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
    if error != nil{
        return
    }
    
    guard let imageData = photo.fileDataRepresentation() else{return}
    self.picData = imageData
}

func sendPicData(){
    let image = UIImage(data: self.picData)
    let imageData: Data = image?.jpegData(compressionQuality: 0.1) ?? Data()
    let imageString: String = imageData.base64EncodedString()
            
    let dictionary:[String:String] = ["Dot":imageString]
    if let theJSONData = try? JSONSerialization.data(withJSONObject: dictionary, options: [.prettyPrinted]) {

        guard let sendURL = URL(string:"http://toServer") else {
            print("invalid URL")
            return
        }
        var request = URLRequest(url: sendURL)
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.setValue("application/json", forHTTPHeaderField: "Accept")
        request.httpMethod = "POST"
        request.httpBody = theJSONData

        URLSession.shared.dataTask(with: request) {data, response, error in
            guard data != nil else {
                print ("PUT Failed: \(error?.localizedDescription ?? "Unknown Error")")
                return
            }
        }.resume()

        print(dictionary)
    }
}
}

我不知道为什么这么不一致。这对我来说没有任何意义，如果它一次有效，为什么不是每次都有效？请帮忙

Answer 1

问题是委托函数 func photoOutput() 并没有在每次拍照时都被调用。我发现在 func takePic() 中，如果我将 Timer 放在 self.session.stopRunning() 上，它会解决问题并每次都调用委托函数，但它也会导致另一个问题，即停止调用 self.isTaken.toggle()。为了解决这个问题，我把 Timer 放在 DispatchQueue.main.async 中，像这样

func takePic(){
    DispatchQueue.global(qos: .background).async {
        self.output.capturePhoto(with: AVCapturePhotoSettings(), delegate: self)
        DispatchQueue.main.async {
            Timer.scheduledTimer(withTimeInterval: 0.1, repeats: false) { (timer) in
                self.session.stopRunning()
            }
        }
        
        DispatchQueue.main.async {
            withAnimation{self.isTaken.toggle()}
        }
        print("pic taken...")
    }
}

我不确定这是否是解决此问题的最佳方法，但我见过很多其他人遇到同样类似的问题，并且使用此解决方案每次都会调用委托函数。

Answer 2

你为什么要切换 isTaken 之前（它是）。

我认为这里的问题是您允许在拍照线程完成之前保存照片（显示按钮）。

func takePic(){
    DispatchQueue.global(qos: .background).async {
        self.output.capturePhoto(with: AVCapturePhotoSettings(), delegate: self)
        self.session.stopRunning()
        
        //DispatchQueue.main.async {
        //    withAnimation{self.isTaken.toggle()}  // << IT ISNT TAKEN YET
        //}
        //print("pic taken...")  // << AGAIN IT ISNT TAKEN YET
    }
}

当 takePic 线程完成时，它调用委托（回调）：

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {

    // NOW ITS TAKEN BUT MAY HAVE ERRORS

    if error != nil{
        return  // MAYBE THIS NEED SOME BETTER FEEDBACK FOR THE USER
    }
    
    guard let imageData = photo.fileDataRepresentation() else{return}  // USER FEEDBACK??

    self.picData = imageData

    // NOW ITS TAKEN


    // I'm assuming this is running on the main thread.
    withAnimation{self.isTaken.toggle()} // SO TOGGLE isTaken
}

我在没有测试的情况下写这篇文章，但我认为你混淆了回调的工作原理。

https://en.wikipedia.org/wiki/Callback_%28computer_programming%29

这里的 func photoOutput 是回调（除非我在这里遗漏了一些东西，因为我自己对 SwiftUI 还很陌生）。

SwiftUI- 服务器未接收到 base64 字符串

SwiftUI- server not receiving base64 string

post

base64

json

swift