如何从WinUI控件的框架中的页中检索当前WinUI 3 MainWindow的窗口句柄

Question

我正在创建我的第一个WinUI 3桌面应用程序。我的NavigationView在我的MainWindow上。我通过NavigationView中的框架导航到9个不同的页面。其中一页用于打印报告。我需要让FileSavePicker从“reportPage”开始工作。我直接按照learn.microsoft.com的示例实现了下面的内容。(我还在下面添加了同样的FileSavePicker代码段到一个小型虚拟winui-3沙箱测试应用程序中，但我将代码放在MainWindow的代码背后，它运行得很好。)我需要让FileSavePicker从一个页面而不是一个MainWindow来工作。到目前为止，谢谢大家的帮助。

我得到了这个调试错误：

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我知道问题与获得主窗口的HWND有关。

// Retrieve the window handle (HWND) of the current WinUI 3 window.
   var window = (MainWindow)Application.Current.MainWindow; (I tried this, but it did not work)

我从上面的一行中得到了这个错误：

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(我试过了，但没有用)

   var hWnd = WinRT.Interop.WindowNative.GetWindowHandle(window); 

我从上面的一行中得到了这个错误：

​

​

我不知道正确的语法。

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;
using System;
using System.Collections.Generic;
using Windows.Storage;
using Windows.Storage.Pickers;
using Windows.Storage.Provider;
    
namespace MetricReporting.Pages
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class pageReports : Page
    {
        public pageReports()
        {
            this.InitializeComponent();
        }

        private void ButtonBoltReport_Click(object sender, RoutedEventArgs e)
        {
            DisplayBOLTSaveDialog();
        }

        private async void DisplayBOLTSaveDialog()
        {

            FileSavePicker savePicker = new FileSavePicker();

            // Retrieve the window handle (HWND) of the current WinUI 3 window.
            var window = (MainWindow)Application.Current.MainWindow;
            var hWnd = WinRT.Interop.WindowNative.GetWindowHandle(this);

            // Initialize the folder picker with the window handle (HWND).
            WinRT.Interop.InitializeWithWindow.Initialize(savePicker, hWnd);

            savePicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
            // Dropdown of file types the user can save the file as
            savePicker.FileTypeChoices.Add("Plain Text", new List<string>() { ".txt" });
            // Default file name if the user does not type one in or select a file to replace
            savePicker.SuggestedFileName = "New Document";

            StorageFile file = await savePicker.PickSaveFileAsync();
            if (file != null)
            {
                // Prevent updates to the remote version of the file until we finish making changes and call CompleteUpdatesAsync.
                CachedFileManager.DeferUpdates(file);
                // write to file
                await FileIO.WriteTextAsync(file, file.Name);
                // Let Windows know that we're finished changing the file so the other app can update the remote version of the file.
                // Completing updates may require Windows to ask for user input.
                FileUpdateStatus status = await CachedFileManager.CompleteUpdatesAsync(file);
                if (status == FileUpdateStatus.Complete)
                {
                    ReportStatus.Text = "File " + file.Name + " was saved.";
                }
                else
                {
                    ReportStatus.Text = "File " + file.Name + " couldn't be saved.";
                }
            }
            else
            {
                ReportStatus.Text = "Operation cancelled.";
            }
            
        }
    }
}

Answer 1

更改m_window字段在App.xaml.cs中的修饰符：

internal Window m_window;

...or最好通过一个属性公开它：

public Window Window => m_window;

然后，您可以像这样从页面访问窗口：

var window = (Application.Current as App)?.m_window as MainWindow; 

或

var window = (Application.Current as App)?.Window as MainWindow;