.NET MAUI实战 FolderPicker

1.概要

最近在迁移 GeneralUpdate.Tool的时候需要用到文件夹选择，在MAUI中可以使用FolderPicker进行选择。注意，和上篇文章的文件选择不一样。因为在.NET MAUI中目前还没有傻瓜式直接可用的FolderPicker供开发者使用所以需要自己动手做一些修改。

完整示例代码：https://gitee.com/Juster-zhu/GeneralUpdate/tree/master/src/c%23/GeneralUpdate.PacketTool

2.详细内容

实现步骤如下：

定义接口

public interface IFolderPickerService{Task<string> PickFolderTaskAsync();}

2.在每个受支持的平台上实现接口

using GeneralUpdate.Infrastructure.DataServices.Pick;
using WindowsFolderPicker = Windows.Storage.Pickers.FolderPicker;namespace GeneralUpdate.PacketTool.Platforms.Windows
{public class FolderPicker : IFolderPickerService{public async Task<string> PickFolderTaskAsync(){var folderPicker = new WindowsFolderPicker();// Might be needed to make it work on Windows 10folderPicker.FileTypeFilter.Add("*");// Get the current window's HWND by passing in the Window objectvar hwnd = ((MauiWinUIWindow)App.Current.Windows[0].Handler.PlatformView).WindowHandle;// Associate the HWND with the file pickerWinRT.Interop.InitializeWithWindow.Initialize(folderPicker, hwnd);var result = await folderPicker.PickSingleFolderAsync();return result?.Path;}}
}

3.向.NET MAUI框架容器中注入FolderPicker注册实现

一定需要记住下面代码中的这个using引用。

using GeneralUpdate.Infrastructure.DataServices.Pick;

不可以删除因为加入了环境的判断会导致在编码时认为是无效应用，实际运行时会使用到该命名空间。

#if WINDOWSmauiAppBuilder.Services.AddTransient<IFolderPickerService, Platforms.Windows.FolderPicker>();
#elif MACCATALYSTmauiAppBuilder.Services.AddTransient<IFolderPickerService, Platforms.MacCatalyst.FolderPicker>();
#endif

实际代码如下。

using GeneralUpdate.Infrastructure.DataServices.Pick;
using GeneralUpdate.PacketTool.ViewModels;namespace GeneralUpdate.PacketTool
{public static class MauiProgram{public static MauiApp CreateMauiApp(){var builder = MauiApp.CreateBuilder();builder.UseMauiApp<App>().RegisterViewModels().RegisterView().RegisterAppServices().RegisterOther().ConfigureFonts(fonts =>{fonts.AddFont("OpenSans-Regular.ttf", "OpenSansRegular");fonts.AddFont("OpenSans-Semibold.ttf", "OpenSansSemibold");});return builder.Build();}public static MauiAppBuilder RegisterOther(this MauiAppBuilder mauiAppBuilder){mauiAppBuilder.Services.AddTransient<App>();return mauiAppBuilder;}public static MauiAppBuilder RegisterView(this MauiAppBuilder mauiAppBuilder){mauiAppBuilder.Services.AddTransient<MainPage>();return mauiAppBuilder;}public static MauiAppBuilder RegisterViewModels(this MauiAppBuilder mauiAppBuilder){mauiAppBuilder.Services.AddTransient<MainViewModel>();return mauiAppBuilder;}public static MauiAppBuilder RegisterAppServices(this MauiAppBuilder mauiAppBuilder){
#if WINDOWSmauiAppBuilder.Services.AddTransient<IFolderPickerService, Platforms.Windows.FolderPicker>();
#elif MACCATALYSTmauiAppBuilder.Services.AddTransient<IFolderPickerService, Platforms.MacCatalyst.FolderPicker>();
#endifreturn mauiAppBuilder;}}
}

4.使用功能

如何使用

将我们刚刚在容器中注入好的FolderPickerService取出来，并初始化ViewModel中的引用。

public class MainViewModel : ViewModeBase{//code...public MainViewModel(IFolderPickerService folderPickerService) {_folderPickerService = folderPickerService;}//code...}

FolderPickerService调用。

/// <summary>/// Choose a path/// </summary>/// <param name="value"></param>private async Task SelectFolderAction(string value){var pickerResult = await _folderPickerService.PickFolderTaskAsync();if (pickerResult == null){await Shell.Current.DisplayAlert("Pick options", "No results were selected !", "ok");return;}switch (value){case "Source":SourcePath = pickerResult;break;case "Target":TargetPath = pickerResult;break;case "Patch":PatchPath = pickerResult;break;}}