android把U盘的uri转为路径

在 Android 11 中，访问外部存储需要申请 `MANAGE_EXTERNAL_STORAGE` 权限。如果没有申请该权限，会导致访问外部存储时出现错误。

可以参考以下代码，在 `AndroidManifest.xml` 文件中申请该权限：

<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />

同时，在运行时也需要动态申请该权限。

以下是将 U 盘的 Uri 转换为路径的示例代码：

public class FileUtils {
    public static String getUsbDiskPath(Context context) {
        String usbDiskPath = null;
        File[] dirs = ContextCompat.getExternalFilesDirs(context, null);
        for (File dir : dirs) {
            if (dir != null && dir.exists() && dir.isDirectory() && dir.canWrite()) {
                String dirPath = dir.getAbsolutePath();
                if (dirPath.startsWith("/storage/")) {
                    // 内置存储
                    continue;
                } else {
                    // 外置存储
                    usbDiskPath = dirPath;
                    break;
                }
            }
        }
        return usbDiskPath;
    }

    public static String getRealPathFromUri(Context context, Uri uri) {
        String realPath = null;
        if (DocumentsContract.isDocumentUri(context, uri)) {
            if (isExternalStorageDocument(uri)) {
                // 外部存储
                String docId = DocumentsContract.getDocumentId(uri);
                String[] split = docId.split(":");
                String type = split[0];
                if ("primary".equalsIgnoreCase(type)) {
                    realPath = Environment.getExternalStorageDirectory() + "/" + split[1];
                } else {
                    String usbDiskPath = getUsbDiskPath(context);
                    if (usbDiskPath != null) {
                        realPath = usbDiskPath + "/" + split[1];
                    }
                }
            } else if (isDownloadsDocument(uri)) {
                // 下载目录
                String id = DocumentsContract.getDocumentId(uri);
                Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));
                realPath = getDataColumn(context, contentUri, null, null);
            } else if (isMediaDocument(uri)) {
                // 媒体库
                String docId = DocumentsContract.getDocumentId(uri);
                String[] split = docId.split(":");
                String type = split[0];
                Uri contentUri = null;
                if ("image".equals(type)) {
                    contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
                } else if ("video".equals(type)) {
                    contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
                } else if ("audio".equals(type)) {
                    contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
                }
                String selection = "_id=?";
                String[] selectionArgs = new String[]{split[1]};
                realPath = getDataColumn(context, contentUri, selection, selectionArgs);
            }
        } else if (ContentResolver.SCHEME_FILE.equalsIgnoreCase(uri.getScheme())) {
            // 直接从文件中获取
            realPath = uri.getPath();
        }
        return realPath;
    }

    private static String getDataColumn(Context context, Uri uri, String selection, String[] selectionArgs) {
        Cursor cursor = null;
        String column = "_data";
        String[] projection = {column};
        try {
            cursor = context.getContentResolver().query(uri, projection, selection, selectionArgs, null);
            if (cursor != null && cursor.moveToFirst()) {
                int index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(index);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (cursor != null) {
                cursor.close();
            }
        }
        return null;
    }

    private static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    private static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    private static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }
}

该工具类中的 `getRealPathFromUri` 方法可以将 U 盘的 Uri 转换为路径。具体实现是根据 Uri 的不同类型，采用不同的方式获取路径。