swift - 如何在 macOS 的 SwiftUI 中使用菜单命令实现多窗口？

Question

情况
实现一个多窗口应用程序，其中每个窗口都有自己的状态。
示例
这是一个展示问题的示例( on github ):

import SwiftUI

@main
struct multi_window_menuApp: App {

  var body: some Scene {
    WindowGroup {
      ContentView()
    }.commands {
      MenuCommands()
    }
  }
}

struct ContentView: View {
  @StateObject var viewModel: ViewModel  = ViewModel()
  
  var body: some View {
    TextField("", text: $viewModel.inputText)
      .disabled(true)
      .padding()
  }
}

public class ViewModel: ObservableObject {
  
  @Published var inputText: String = "" {
    didSet {
      print("content was updated...")
    }
  }
}

问题
我们应该如何以编程方式找出当前选择的 View 是什么，以便我们可以在菜单命令即将完成时更新状态并更新 View 模型中的状态？

import Foundation
import SwiftUI
import Combine

struct MenuCommands: Commands {
  
  var body: some Commands {
    CommandGroup(after: CommandGroupPlacement.newItem, addition: {
      Divider()
      Button(action: {
        let dialog = NSOpenPanel();
        
        dialog.title = "Choose a file";
        dialog.showsResizeIndicator = true;
        dialog.showsHiddenFiles = false;
        dialog.allowsMultipleSelection = false;
        dialog.canChooseDirectories = false;
        
        if (dialog.runModal() ==  NSApplication.ModalResponse.OK) {
          let result = dialog.url
          if (result != nil) {
            let path: String = result!.path
            do {
              let string = try String(contentsOf: URL(fileURLWithPath: path), encoding: .utf8)
              print(string)
              // how to get access to the currently active view model to update the inputText variable?
              // viewModel.inputText = string
            }
            catch {
              print("Error \(error)")
            }
          }
        } else {
          return
        }
      }, label: {
        Text("Open File")
      })
      .keyboardShortcut("O", modifiers: .command)
    })
  }
}

可能有助于解决此问题的链接:

http://www.gfrigerio.com/build-a-macos-app-with-swiftui/

https://troz.net/post/2021/swiftui_mac_menus/

https://onmyway133.com/posts/how-to-manage-windowgroup-in-swiftui-for-macos/

Answer 1

有用的链接:

How to access NSWindow from @main App using only SwiftUI?

How to access own window within SwiftUI view?

https://lostmoa.com/blog/ReadingTheCurrentWindowInANewSwiftUILifecycleApp/

(这是我能够想出的，如果有人有更好的想法/方法，请分享)
这个想法是创建一个共享的“全局” View 模型来跟踪打开的窗口和 View 模型。每个NSWindow有一个唯一的属性 windowNumber .当一个窗口变为事件(键)时，它会通过 windowNumber 查找 View 模型。并将其设置为 activeViewModel .

import SwiftUI

class GlobalViewModel : NSObject, ObservableObject {
  
  // all currently opened windows
  @Published var windows = Set<NSWindow>()
  
  // all view models that belong to currently opened windows
  @Published var viewModels : [Int:ViewModel] = [:]
  
  // currently active aka selected aka key window
  @Published var activeWindow: NSWindow?
  
  // currently active view model for the active window
  @Published var activeViewModel: ViewModel?
  
  func addWindow(window: NSWindow) {
    window.delegate = self
    windows.insert(window)
  }
  
  // associates a window number with a view model
  func addViewModel(_ viewModel: ViewModel, forWindowNumber windowNumber: Int) {
    viewModels[windowNumber] = viewModel
  }
}

然后，对窗口上的每个更改使用react(当它关闭时以及当它变成事件的又名关键窗口时):

import SwiftUI

extension GlobalViewModel : NSWindowDelegate {
  func windowWillClose(_ notification: Notification) {
    if let window = notification.object as? NSWindow {
      windows.remove(window)
      viewModels.removeValue(forKey: window.windowNumber)
      print("Open Windows", windows)
      print("Open Models", viewModels)
    }
  }
  func windowDidBecomeKey(_ notification: Notification) {
    if let window = notification.object as? NSWindow {
      print("Activating Window", window.windowNumber)
      activeWindow = window
      activeViewModel = viewModels[window.windowNumber]
    }
  }
}

提供一种查找与当前 View 关联的窗口的方法:

import SwiftUI

struct HostingWindowFinder: NSViewRepresentable {
  var callback: (NSWindow?) -> ()
  
  func makeNSView(context: Self.Context) -> NSView {
    let view = NSView()
    DispatchQueue.main.async { [weak view] in
      self.callback(view?.window)
    }
    return view
  }
  func updateNSView(_ nsView: NSView, context: Context) {}
}

这是使用当前窗口和 viewModel 更新全局 View 模型的 View :

import SwiftUI

struct ContentView: View {
  @EnvironmentObject var globalViewModel : GlobalViewModel
  
  @StateObject var viewModel: ViewModel  = ViewModel()
  
  var body: some View {
    HostingWindowFinder { window in
      if let window = window {
        self.globalViewModel.addWindow(window: window)
        print("New Window", window.windowNumber)
        self.globalViewModel.addViewModel(self.viewModel, forWindowNumber: window.windowNumber)
      }
    }
    
    TextField("", text: $viewModel.inputText)
      .disabled(true)
      .padding()
  }
}

然后我们需要创建全局 View 模型并将其发送到 View 和命令:

import SwiftUI

@main
struct multi_window_menuApp: App {
  
  @State var globalViewModel = GlobalViewModel()
  
  var body: some Scene {
    WindowGroup {
      ContentView()
        .environmentObject(self.globalViewModel)
    }
    .commands {
      MenuCommands(globalViewModel: self.globalViewModel)
    }
    
    Settings {
      VStack {
        Text("My Settingsview")
      }
    }
  }
}

以下是命令的外观，因此它们可以访问当前选择的/事件的 viewModel:

import Foundation
import SwiftUI
import Combine

struct MenuCommands: Commands {
  var globalViewModel: GlobalViewModel
  
  var body: some Commands {
    CommandGroup(after: CommandGroupPlacement.newItem, addition: {
      Divider()
      Button(action: {
        let dialog = NSOpenPanel();
        
        dialog.title = "Choose a file";
        dialog.showsResizeIndicator = true;
        dialog.showsHiddenFiles = false;
        dialog.allowsMultipleSelection = false;
        dialog.canChooseDirectories = false;
        
        if (dialog.runModal() ==  NSApplication.ModalResponse.OK) {
          let result = dialog.url
          if (result != nil) {
            let path: String = result!.path
            do {
              let string = try String(contentsOf: URL(fileURLWithPath: path), encoding: .utf8)
              print("Active Window", self.globalViewModel.activeWindow?.windowNumber)
              self.globalViewModel.activeViewModel?.inputText = string
            }
            catch {
              print("Error \(error)")
            }
          }
        } else {
          return
        }
      }, label: {
        Text("Open File")
      })
      .keyboardShortcut("O", modifiers: [.command])
    })
  }
}

在这个 github 项目下所有更新和运行:https://github.com/ondrej-kvasnovsky/swiftui-multi-window-menu