直接贴代码：

 @RequiresApi(api = Build.VERSION_CODES.KITKAT)
    public static String getpath(Context context, Uri uri){
        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)) {
                        String 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));
                    String 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]};
                    String 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());
    }