SwiftUI 2.0：使用 .fileExporter 修饰符导出图像

Question

目标：使用新的 .fileExporter 修饰符通过 SwiftUI 导出图像

问题：目标图像未传递到 .fileExporter 文档。

问：如何获取导出图片的.fileExporter修改器？

struct ContentView: View {
    
    @State private var openFile = false
    @State private var exportFile = false


    @State private var img1 = UIImage()
    @State private var img2 = UIImage()

    @State private var target: Binding<UIImage>?    // dynamic target for importer
    
    var body: some View {
        Form {
            //image 1
            Button(action: {
                    self.target = $img1
                self.openFile.toggle()
            }){
                
                Image(uiImage: self.img1)
                .renderingMode(.original)
                .resizable()
                .frame(width: 48, height: 48)
                .clipShape(Circle())
            }
            
            //image 2
            Button(action: {
                    self.target = $img2
                self.openFile.toggle()
            }){
                
                Image(uiImage: self.img2)
                .renderingMode(.original)
                .resizable()
                .frame(width: 48, height: 48)
                .clipShape(Circle())
            }
        }
        .navigationTitle("File Importer")


        //file exporter not working. not sure what I should input as "document"
        .fileExporter(isPresented: $exportFile, document: target, contentType: .image) { result in
            if case .success = result {
                // Handle success.
            } else {
                // Handle failure.
            }
        }

        //file importer
        .fileImporter(isPresented: $openFile, allowedContentTypes: [.image]) { (res) in
            do{
                let fileUrl = try res.get()
                print(fileUrl)
                
                guard fileUrl.startAccessingSecurityScopedResource() else { return }
                if let imageData = try? Data(contentsOf: fileUrl),
                let image = UIImage(data: imageData) {
                    self.target?.wrappedValue = image
                }
                fileUrl.stopAccessingSecurityScopedResource()
                
            } catch{
                
                print ("error reading")
                print (error.localizedDescription)
            }
        }
    }
}

Answer 1

我发现了一些代码问题和一些逻辑问题。这是我编辑的版本：

struct ContentView: View {
    
    @State private var openFile = false
    @State private var exportFile = false


    @State private var img1 = UIImage(named: "0")!
    @State private var img2 = UIImage(named: "1")!

    @State private var target : UIImage?
    
    var body: some View {
        Form {
            //image 1
            Button(action: {
                self.target = img1
                self.exportFile.toggle()
                //self.openFile.toggle()
            }){
                
                Image(uiImage: self.img1)
                .renderingMode(.original)
                .resizable()
                .frame(width: 48, height: 48)
                .clipShape(Circle())
            }
            
            //image 2
            Button(action: {
                self.target = img2
                self.exportFile.toggle()
                //self.openFile.toggle()
            }){
                
                Image(uiImage: self.img2)
                .renderingMode(.original)
                .resizable()
                .frame(width: 48, height: 48)
                .clipShape(Circle())
            }
        }
        .navigationTitle("File Importer")

        .fileExporter(isPresented: $exportFile, document: ImageDocument(image: target), contentType: .png, onCompletion: { (result) in
            if case .success = result {
                print("Success")
            } else {
                print("Failure")
            }
        })


        //file importer
        .fileImporter(isPresented: $openFile, allowedContentTypes: [.image]) { (res) in
            do{
                let fileUrl = try res.get()
                print(fileUrl)
                
                guard fileUrl.startAccessingSecurityScopedResource() else { return }
                if let imageData = try? Data(contentsOf: fileUrl),
                let image = UIImage(data: imageData) {
                    self.target = image
                }
                fileUrl.stopAccessingSecurityScopedResource()
                
            } catch{
                
                print ("error reading")
                print (error.localizedDescription)
            }
        }
    }
}

struct ImageDocument: FileDocument {
    
    static var readableContentTypes: [UTType] { [.png] }

    var image: UIImage

    init(image: UIImage?) {
        self.image = image ?? UIImage()
    }

    init(configuration: ReadConfiguration) throws {
        guard let data = configuration.file.regularFileContents,
              let image = UIImage(data: data)
        else {
            throw CocoaError(.fileReadCorruptFile)
        }
        self.image = image
    }

    func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
        return FileWrapper(regularFileWithContents: image.pngData()!)
    }
    
}

要看的东西：

逻辑错误：您有一个 exportFile 状态变量，但您从未修改过它。这意味着 fileExporter 永远不会出现。
您将 Binding<UIImage> 传递给需要 FileDocument 的函数。我为图像编写了一个简单的 FileDocument 实现。
因为我关闭了 openFile 的 exportFile 开关，您现在没有任何 openFile 访问权限。这是一个合乎逻辑的决定，你需要找出 when/how 来触发这些。
我也没有对图像进行任何错误处理，并决定将所有内容都视为 PNG。您可能想要做出不同的选择。

请注意，我还使用了名为“0”和“1”的图像——它们是我的示例项目特有的。更改这些以适合您的项目。

如果您想要不同类型的解决方案，您还可以查看使用 \.exportFiles 操作：https://www.hackingwithswift.com/quick-start/swiftui/how-to-export-files-using-exportfilesaction

SwiftUI 2.0：使用 .fileExporter 修饰符导出图像

SwiftUI 2.0: export images with .fileExporter modifier

swiftui

ios14

xcode12

macos-big-sur