使用SwiftUIView作為NSSavePanel的附件視圖時的奇怪行為

我正在嘗試使用用 SwiftUI 撰寫的視圖作為我的附件視圖，NSSavePanel但我很難讓它正常作業。

這是我的 SwiftUI 視圖的實作：

struct ExportAccessoryView: View {
    enum ExportFileType: String, Identifiable {
        // ... enum declaration
    }
    
    @State var selectedExportFileType: ExportFileType = .png
    @State var resolution = 256.0
    
    @Binding var selectedFileTypeBinding: ExportFileType
    @Binding var resolutionBinding: Double
    
    var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            Picker(selection: $selectedExportFileType, label: Text("Format:")) {
                Text("PDF").tag(ExportFileType.pdf)
                // ... other items
            }
            .frame(width: 170)
            .padding(.leading, 21)
            if [ExportFileType.png, ExportFileType.jpeg, ExportFileType.tiff].contains(selectedExportFileType) {
                HStack {
                    Slider(value: $resolution, in: 128...1024,
                           label: { Text("Resolution:") })
                        .frame(width: 200)
                    Text("\(Int(resolution))")
                        .frame(width: 40, alignment: .leading)
                        .padding(.leading, 5)
                }
            }
        }
        .padding(10)
        .onChange(of: selectedExportFileType) { newValue in
            self.selectedFileTypeBinding = newValue
        }
        .onChange(of: resolution) { newValue in
            self.resolutionBinding = newValue
        }
    }
}

這是我實作保存面板的方式：

class DocumentWindow: NSWindowController {
    
    var exportFileType: ExportAccessoryView.ExportFileType = .pdf
    var resolution = 256.0
    
    lazy var exportPanel: NSSavePanel = {
        let savePanel = NSSavePanel()
        savePanel.message = "Specify where and how you wish to export..."
        savePanel.nameFieldLabel = "Export As:"
        savePanel.canCreateDirectories = true
        savePanel.isExtensionHidden = false
        savePanel.showsTagField = true
        
        let fileTypeBinding = Binding {
            return self.exportFileType
        } set: { newValue in
            self.exportFileType = newValue
            // update file extension
            self.exportPanel.allowedContentTypes = [UTType(newValue.rawValue)!]
        }
        let resolutionBinding = Binding {
            return self.resolution
        } set: { newValue in
            self.resolution = newValue
        }

        let accessoryView = ExportAccessoryView(selectedFileTypeBinding: fileTypeBinding,
                                                resolutionBinding: resolutionBinding)
        let exportAccessoryView = NSHostingController(rootView: accessoryView)
        
        savePanel.accessoryView = exportAccessoryView.view
        
        savePanel.allowedContentTypes = [UTType(self.exportFileType.rawValue)!]
        
        return savePanel
    }()
}

保存面板通過呼叫來呈現beginSheetModal(for:completionHandler:)。

它顯示沒有問題，但附件視圖表現出一些奇怪的行為：它似乎在隨機做自己的事情（我尋找模式但我沒有這樣做）。

有時它可以正常作業，有時它變得不可點擊（但該功能仍然可以通過使用 的開關控制來訪問TAB）。對齊方式總是與我上次展開/折疊或打開/關閉面板時不同：有時它左對齊，有時它居中（即使我已明確選擇.leading對齊）。

我完全不知道發生了什么。我不知道這是否是 SwiftUI AppKit 的問題，還是我做錯了，這很可能是因為我是 SwiftUI 的新手。我應該怎么做才能讓它正常作業？

uj5u.com熱心網友回復：

我記得以前我使用 XIB 實作附件視圖的時候：我曾經將控制元件嵌入到 an 中NSView，然后設定約束以使其作業。所以我在這里應用了相同的想法，將NSHostingView's嵌入到view自定義中NSView，并在對其進行了一些調整之后，我讓它作業了：

lazy var exportPanel: NSSavePanel = {
    // ... setting up save panel

    // instantiate SwiftUI view and its hosting controller
    let accessoryView = ExportAccessoryView(selectedFileTypeBinding: fileTypeBinding,
                                            resolutionBinding: resolutionBinding)
    let exportAccessoryView = NSHostingController(rootView: accessoryView)

    // embed the SwiftUI in a custom view
    let customView = NSView(frame: NSRect(x: 0, y: 0, width: 300, height: 60))
    customView.addSubview(exportAccessoryView.view)

    // use my own constraints
    exportAccessoryView.view.translatesAutoresizingMaskIntoConstraints = false

    // top and bottom clipped to custom view
    exportAccessoryView.view.topAnchor.constraint(equalTo: customView.topAnchor).isActive = true
    exportAccessoryView.view.bottomAnchor.constraint(equalTo: customView.bottomAnchor).isActive = true

    // leading and trailing spaces can stretch as far as they need to be, hence ≥0
    exportAccessoryView.view.leadingAnchor.constraint(greaterThanOrEqualTo: customView.leadingAnchor).isActive = true
    exportAccessoryView.view.trailingAnchor.constraint(greaterThanOrEqualTo: customView.trailingAnchor).isActive = true

    // center the SwiftUI view horizontal within custom view
    exportAccessoryView.view.centerXAnchor.constraint(equalTo: customView.centerXAnchor).isActive = true

    // usually fixed width and height
    // can be flexible when SwiftUI view is dynamic
    exportAccessoryView.view.widthAnchor.constraint(equalToConstant: customView.frame.width).isActive = true
    exportAccessoryView.view.heightAnchor.constraint(greaterThanOrEqualToConstant: customView.frame.height).isActive = true

    savePanel.accessoryView = customView

    // ... additional setup

    return savePanel
}()

現在它可以按預期完美運行。不知道這是否是實作這種集成的“正確方法”。

標籤：迅速 可可 迅捷 保存面板

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