之前在工作的过程中，遇到不同 Android 版本下 URI 采用不同方式来获取文件路径的问题。

因为需求的原因，要求拍照上传或者从相册中选择图片上传，而且图片是需要经过压缩的，大小不能超过2M。

很快，拍照的这部分就搞定了。那么相册中选择图片的也是一样的道理，应该也是轻松解决了。

至于选择图片的代码，如下所示：

intent = new Intent(Intent.ACTION_GET_CONTENT);
intent.addCategory(Intent.CATEGORY_OPENABLE);
intent.setType("image/*");
startActivityForResult(intent, FILE_CHOOSER_RESULT_CODE);

之后就是在 onActivityResult(int requestCode, int resultCode, Intent data) 中获取到 URI 。

最关键的来了，如果通过 URI 来获取文件呢？

比如，现在 URI 为 content://media/extenral/images/media/17766 ，而我们需要得到对应的文件路径。

if (ContentResolver.SCHEME_CONTENT.equals(uri.getScheme())) {
    Cursor cursor = context.getContentResolver().query(uri, new String[]{MediaStore.Images.Media.DATA}, null, null, null);
    if (cursor != null) {
        if (cursor.moveToFirst()) {
            int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
            if (columnIndex > -1) {
                path = cursor.getString(columnIndex);
            }
        }
        cursor.close();
    }
    return path;
}

原以为万事大吉，但是在 Android 4.4 及以上的手机上一试，发现根本不行。因为在 Android 4.4 及以上的手机上，获取到的 URI 变成了 content://com.android.providers.media.documents/document/image%3A235700 ，和之前我们预期的不是同一种类型。

这是因为在 Android 4.4 及以上的机型，使用了 DocumentUri 来代表获取到文件的 URI 。

所以我们又要对于 DocumentUri 进行适配。

if (ContentResolver.SCHEME_CONTENT.equals(uri.getScheme())) {
       if (DocumentsContract.isDocumentUri(context, uri)) {
           if (isExternalStorageDocument(uri)) {
               // ExternalStorageProvider
               final String docId = DocumentsContract.getDocumentId(uri);
               final String[] split = docId.split(":");
               final String type = split[0];
               if ("primary".equalsIgnoreCase(type)) {
                   path = Environment.getExternalStorageDirectory() + "/" + split[1];
                   return path;
               }
           } else if (isDownloadsDocument(uri)) {
               // DownloadsProvider
               final String id = DocumentsContract.getDocumentId(uri);
               final Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),
                       Long.valueOf(id));
               path = getDataColumn(context, contentUri, null, null);
               return path;
           } else if (isMediaDocument(uri)) {
               // MediaProvider
               final String docId = DocumentsContract.getDocumentId(uri);
               final String[] split = docId.split(":");
               final 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;
               }
               final String selection = "_id=?";
               final String[] selectionArgs = new String[]{split[1]};
               path = getDataColumn(context, contentUri, selection, selectionArgs);
               return path;
           }
       }
   }

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

好了，上面的代码还是容易看懂的。这下就解决了对于 Android 4.4 及以上的机型适配。顺便把以 file:// 开头的 URI 适配也补上：

if (ContentResolver.SCHEME_FILE.equals(uri.getScheme())) {
    path = uri.getPath();
    return path;
}

完美了，下面就贴出完整的 FileUtils 代码，拿去用吧：

public final class FileUtils {

    public static String getFilePathByUri(Context context, Uri uri) {
        String path = null;
        // 以 file:// 开头的
        if (ContentResolver.SCHEME_FILE.equals(uri.getScheme())) {
            path = uri.getPath();
            return path;
        }
        // 以 content:// 开头的，比如 content://media/extenral/images/media/17766
        if (ContentResolver.SCHEME_CONTENT.equals(uri.getScheme()) && Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
            Cursor cursor = context.getContentResolver().query(uri, new String[]{MediaStore.Images.Media.DATA}, null, null, null);
            if (cursor != null) {
                if (cursor.moveToFirst()) {
                    int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);
                    if (columnIndex > -1) {
                        path = cursor.getString(columnIndex);
                    }
                }
                cursor.close();
            }
            return path;
        }
        // 4.4及之后的 是以 content:// 开头的，比如 content://com.android.providers.media.documents/document/image%3A235700
        if (ContentResolver.SCHEME_CONTENT.equals(uri.getScheme()) && Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            if (DocumentsContract.isDocumentUri(context, uri)) {
                if (isExternalStorageDocument(uri)) {
                    // ExternalStorageProvider
                    final String docId = DocumentsContract.getDocumentId(uri);
                    final String[] split = docId.split(":");
                    final String type = split[0];
                    if ("primary".equalsIgnoreCase(type)) {
                        path = Environment.getExternalStorageDirectory() + "/" + split[1];
                        return path;
                    }
                } else if (isDownloadsDocument(uri)) {
                    // DownloadsProvider
                    final String id = DocumentsContract.getDocumentId(uri);
                    final Uri contentUri = ContentUris.withAppendedId(Uri.parse("content://downloads/public_downloads"),
                            Long.valueOf(id));
                    path = getDataColumn(context, contentUri, null, null);
                    return path;
                } else if (isMediaDocument(uri)) {
                    // MediaProvider
                    final String docId = DocumentsContract.getDocumentId(uri);
                    final String[] split = docId.split(":");
                    final 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;
                    }
                    final String selection = "_id=?";
                    final String[] selectionArgs = new String[]{split[1]};
                    path = getDataColumn(context, contentUri, selection, selectionArgs);
                    return path;
                }
            }
        }
        return null;
    }

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

}

讲完了，讲完了。

再见！