如何在MAUI应用中读写Android外部存储文件并获取文件列表

一、权限配置 #

首先需要在Android项目中配置必要的存储权限，同时处理动态权限申请（Android 6.0+要求）：

1. 修改AndroidManifest.xml
   在Platforms/Android/AndroidManifest.xml中添加权限声明：

   <!-- Android 12及以下读写权限 -->
   <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
   <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" android:maxSdkVersion="32" />
   <!-- Android 13+ 媒体文件权限 -->
   <uses-permission android:name="android.permission.READ_MEDIA_IMAGES" />
   <uses-permission android:name="android.permission.READ_MEDIA_VIDEO" />
   <uses-permission android:name="android.permission.READ_MEDIA_AUDIO" />
   <!-- 如需访问所有外部存储（需Google Play审核） -->
   <uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" android:minSdkVersion="33" />
   

2. 动态申请权限
   MAUI提供了Permissions类简化权限申请，封装权限检查方法：

   private static async Task<bool> HasStoragePermissionsAsync()
   {
       if (DeviceInfo.Platform != DevicePlatform.Android) return true;
   
       var sdkVersion = (int)Android.OS.Build.VERSION.SdkInt;
       PermissionStatus readStatus, writeStatus;
   
       if (sdkVersion >= 33)
       {
           // Android 13+ 申请媒体读写权限
           readStatus = await Permissions.CheckStatusAsync<Permissions.MediaRead>();
           writeStatus = await Permissions.CheckStatusAsync<Permissions.MediaWrite>();
           if (readStatus != PermissionStatus.Granted)
               readStatus = await Permissions.RequestAsync<Permissions.MediaRead>();
           if (writeStatus != PermissionStatus.Granted)
               writeStatus = await Permissions.RequestAsync<Permissions.MediaWrite>();
       }
       else
       {
           // Android 6-12 申请存储读写权限
           readStatus = await Permissions.CheckStatusAsync<Permissions.StorageRead>();
           writeStatus = await Permissions.CheckStatusAsync<Permissions.StorageWrite>();
           if (readStatus != PermissionStatus.Granted)
               readStatus = await Permissions.RequestAsync<Permissions.StorageRead>();
           if (writeStatus != PermissionStatus.Granted)
               writeStatus = await Permissions.RequestAsync<Permissions.StorageWrite>();
       }
   
       return readStatus == PermissionStatus.Granted && writeStatus == PermissionStatus.Granted;
   }
   

二、获取外部存储路径 #

根据需求选择对应的外部存储目录：

1. 公共存储目录（如Downloads、Documents）
   适用于访问系统公共文件夹的场景：

   // 获取公共Downloads目录路径
   var publicDownloadsPath = Android.OS.Environment
       .GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads)
       .AbsolutePath;
   
   // 获取公共Documents目录路径
   var publicDocumentsPath = Android.OS.Environment
       .GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDocuments)
       .AbsolutePath;
   

2. 应用专属外部存储目录
   该目录属于应用私有，卸载应用时会被清空，无需额外权限：

   var appExternalPath = Android.App.Application.Context
       .GetExternalFilesDir(null)
       .AbsolutePath;
   

三、封装抽象API实现类似Directory.GetFiles #

封装跨平台兼容的方法，在Android平台完成权限校验和文件列表获取：

public static class FileHelper
{
    public static async Task<string[]> GetFilesInFolderAsync(string folderPath)
    {
        if (!await HasStoragePermissionsAsync())
            throw new UnauthorizedAccessException("未获得存储访问权限");

        if (!Directory.Exists(folderPath))
            throw new DirectoryNotFoundException("指定文件夹不存在");

        return Directory.GetFiles(folderPath);
    }

    // 权限检查方法
    private static async Task<bool> HasStoragePermissionsAsync()
    {
        if (DeviceInfo.Platform != DevicePlatform.Android) return true;

        var sdkVersion = (int)Android.OS.Build.VERSION.SdkInt;
        PermissionStatus readStatus, writeStatus;

        if (sdkVersion >= 33)
        {
            readStatus = await Permissions.CheckStatusAsync<Permissions.MediaRead>();
            writeStatus = await Permissions.CheckStatusAsync<Permissions.MediaWrite>();
            if (readStatus != PermissionStatus.Granted)
                readStatus = await Permissions.RequestAsync<Permissions.MediaRead>();
            if (writeStatus != PermissionStatus.Granted)
                writeStatus = await Permissions.RequestAsync<Permissions.MediaWrite>();
        }
        else
        {
            readStatus = await Permissions.CheckStatusAsync<Permissions.StorageRead>();
            writeStatus = await Permissions.CheckStatusAsync<Permissions.StorageWrite>();
            if (readStatus != PermissionStatus.Granted)
                readStatus = await Permissions.RequestAsync<Permissions.StorageRead>();
            if (writeStatus != PermissionStatus.Granted)
                writeStatus = await Permissions.RequestAsync<Permissions.StorageWrite>();
        }

        return readStatus == PermissionStatus.Granted && writeStatus == PermissionStatus.Granted;
    }
}

四、使用示例 #

try
{
    // 替换为你需要访问的文件夹路径
    string targetFolder = "";
    if (DeviceInfo.Platform == DevicePlatform.Android)
    {
        targetFolder = Android.OS.Environment
            .GetExternalStoragePublicDirectory(Android.OS.Environment.DirectoryDownloads)
            .AbsolutePath;
    }

    var files = await FileHelper.GetFilesInFolderAsync(targetFolder);
    // 遍历文件列表做后续处理
    foreach (var file in files)
    {
        Console.WriteLine($"找到文件：{file}");
    }
}
catch (Exception ex)
{
    Console.WriteLine($"出错：{ex.Message}");
}

五、关键注意事项 #

• Scoped Storage限制：Android 10+引入了Scoped Storage，直接使用Directory类访问非应用专属的公共目录可能受限。若需访问更多目录，推荐使用MediaStore或Storage Access Framework（SAF）；若必须用文件路径方式，需申请MANAGE_EXTERNAL_STORAGE权限，但该权限需通过Google Play特殊审核。
• 应用专属存储优先：如果不需要共享文件给其他应用，优先使用应用专属外部存储，无需额外权限且不受Scoped Storage限制。
• 跨平台兼容：若需支持多平台，建议定义抽象接口，在不同平台实现对应的文件操作逻辑，避免代码耦合。

内容的提问来源于stack exchange，提问作者Divya Prakash Jha