如何在macOS上使用SwiftUI显示QLPreviewPanel？

Question

[试图弄清楚如何在iOS和macOS上的SwiftUI中使用QuickLook。我怀疑在不久的将来，将会有一些统一的SwiftUI QL API，但是还看不到它，所以让我们使用已有的东西吧…

如何从SwiftUI视图显示和配置QLPreviewPanel？到目前为止，我有这个：

struct ItemView: View {
    let previewPanelThing = PreviewPanelThing()
    var body: some View {
        Button("OSX preview") {
            print("osx preview")
            if let previewPanel = QLPreviewPanel.shared() {
                self.previewPanelThing.updateControllerForPanel(previewPanel)
                previewPanel.makeKeyAndOrderFront(self.previewPanelThing)
            }                   
        }
    }
}

class PreviewPanelThing: QLPreviewPanelDataSource {

    func updateControllerForPanel(_ panel: QLPreviewPanel) {
        print("updating controller")
        panel.updateController()
    }

    func numberOfPreviewItems(in panel: QLPreviewPanel!) -> Int {
        print("number of items")
        return 1
    }

    func previewPanel(_ panel: QLPreviewPanel!, previewItemAt index: Int) -> QLPreviewItem! {
        print("requesting preview item")
        let fileURL: URL = Bundle.main.url(forResource: "Thinking-of-getting-a-cat", withExtension: "png")!
        return fileURL as QLPreviewItem
    }   
}

这不起作用。我怀疑这是因为QLPreviewPanel文档说：The preview panel follows the responder chain and adapts to the first responder willing to control it.我的previewPanelThing实例不在UI和响应者链中。我不确定响应者链如何在SwiftUI中工作以及如何做到最好。

Answer 1

这里有可能直接使用QLPreviewView预览PDF文件（在此演示中存储在主应用程序包中，但这不会改变普遍的想法）

更新：添加了带有QLPreviewPanel的变体，点击按钮

import SwiftUI
import AppKit
import Quartz

func loadPreviewItem(with name: String) -> NSURL {

    let file = name.components(separatedBy: ".")
    let path = Bundle.main.path(forResource: file.first!, ofType: file.last!)
    let url = NSURL(fileURLWithPath: path!)

    return url
}

struct MyPreview: NSViewRepresentable {
    var fileName: String

    func makeNSView(context: NSViewRepresentableContext<MyPreview>) -> QLPreviewView {
        let preview = QLPreviewView(frame: .zero, style: .normal)
        preview?.autostarts = true
        preview?.previewItem = loadPreviewItem(with: fileName) as QLPreviewItem
        return preview ?? QLPreviewView()
    }

    func updateNSView(_ nsView: QLPreviewView, context: NSViewRepresentableContext<MyPreview>) {
    }

    typealias NSViewType = QLPreviewView

}

struct ContentView: View {
    let qlCoordinator = QLCoordinator()

    var body: some View {

        // example.pdf is expected in app bundle resources
        VStack {
            MyPreview(fileName: "example.pdf")
            Divider()
            Button("Show panel") {
                let panel = QLPreviewPanel.shared()
                panel?.center()
                panel?.dataSource = self.qlCoordinator
                panel?.makeKeyAndOrderFront(nil)
            }
        }
    }

    class QLCoordinator: NSObject, QLPreviewPanelDataSource {
        func previewPanel(_ panel: QLPreviewPanel!, previewItemAt index: Int) -> QLPreviewItem! {
            return loadPreviewItem(with: "example.pdf") as QLPreviewItem
        }

        func numberOfPreviewItems(in controller: QLPreviewPanel) -> Int {
            return 1
        }
    }
}