问题

Both the .fileImporter function (in SwiftUI) and the UIDocumentPickerViewController are shown as intended, but they do not show any contents.
Instead, it says: "Content not available" on the Shared and Recent Icons and "My iPhone is empty" on the Browse Icon.

How did I implement them?
.fileImporter:

var body: some View {
    VStack {
        // ...
    }.padding(.horizontal, 25)
        .fileImporter(isPresented: $selectingFile, allowedContentTypes: [.item], onCompletion: { _ in })
}

UIDocumentPickerViewController:

struct ImportDocumentView: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> some UIViewController {
        let controller = UIDocumentPickerViewController(forOpeningContentTypes: [.item])
        controller.allowsMultipleSelection = false
        return controller
    }

    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
}

What I thought could be the problems:

• Wrong UTType -> tried a load of different options there; none helped.
• Emulator Problem -> I don't have an iPhone to test this. I need to make it work in the emulator. Other people had problems with the emulator, but not showing any data was not one of them.
• Access Permissions -> In my understanding, I should at least have access to the app-specific folder, but even that is not showing. I also tried to set "NSFileProviderDomainAccess" in Info.plist, but that didn't work either. (I might have done something wrong in the process though)

var body: some View {
    VStack {
        // ...
    }.padding(.horizontal, 25)
        .fileImporter(isPresented: $selectingFile, allowedContentTypes: [.item], onCompletion: { _ in })
}

struct ImportDocumentView: UIViewControllerRepresentable {
    func makeUIViewController(context: Context) -> some UIViewController {
        let controller = UIDocumentPickerViewController(forOpeningContentTypes: [.item])
        controller.allowsMultipleSelection = false
        return controller
    }

    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
}

答案1

得分: 0

I found the answer to my own question:
我找到了答案：

I had to "import UniformTypeIdentifiers"
我必须“导入UniformTypeIdentifiers”

Xcode doesn't complain about not having it, it just doesn't show any files or folders. Only indicator was a different color for the element in the allowedContentTypes: [] collection.
Xcode不会因为没有它而抱怨，只是不显示任何文件或文件夹。唯一的指示是allowedContentTypes: []集合中元素的不同颜色。

Edit: For those still not seeing much: the Xcode iPhone Simulator doesn't have any example/inital files or folders in there. I'd recommend to create a folder with the files app on the phone to see some feedback. If you want files in there use Swift's fileExporter.
编辑：对于仍然看不到太多的人：Xcode iPhone模拟器里没有任何示例/初始文件或文件夹。我建议使用手机上的文件应用程序创建一个文件夹以查看一些反馈。如果你想在其中放入文件，请使用Swift的fileExporter。