使用内置文件浏览器浏览PDF文件时获取null

Question

我正在Android中实现表单提交页面，我想将pdf上传到服务器，但此代码在android oreo中不起作用，另一个版本为什么有效？

我在这里得到空指针

file = new File(new FilePath().getPath(getActivity(),filePath));

使用内置文件浏览器浏览文件时。

文件选择器

 private void showFileChooser() {

            Intent intent = new Intent();
            intent.addCategory(Intent.CATEGORY_OPENABLE);
            intent.setType("application/pdf");
            intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
    //        intent.setAction(Intent.ACTION_OPEN_DOCUMENT);
            intent.setAction(Intent.ACTION_GET_CONTENT);
            startActivityForResult(Intent.createChooser(intent, "Select Pdf"), PICK_PDF_REQUEST);

        }

onActivity结果

 @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == PICK_PDF_REQUEST && resultCode == Activity.RESULT_OK && data != null && data.getData() != null) {
final Uri filePath = data.getData();
 filename = filePath.getLastPathSegment();
file = new File(new FilePath().getPath(getActivity(),filePath));
 String filenameArray[] = filename.split("\\.");
            String extension = filenameArray[filenameArray.length - 1];

            if (extension.equals("pdf")) {

               if (isPDF(file)) {
sop(VALID)
}

我尝试了一些简单的方法来获取文件路径，但是这些方法在android中不起作用。这堂课对我有帮助。

获取位置的代码

class FilePath {
    /**
     * Method for return file path of Gallery image
     *
     * @param context
     * @param uri
     * @return path of the selected image file from gallery
     */

    public static String getPath(final Context context, final Uri uri)
    {
        //check here to KITKAT or new version
        final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;

        // DocumentProvider
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
            if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {

                // ExternalStorageProvider
                if (isExternalStorageDocument(uri)) {
                    final String docId = DocumentsContract.getDocumentId(uri);
                    final String[] split = docId.split(":");
                    final String type = split[0];

                    if ("primary".equalsIgnoreCase(type)) {
                        return Environment.getExternalStorageDirectory() + "/" + split[1];
                    }
                }

                //DownloadsProvider
                else if (isDownloadsDocument(uri)) {

                    final String id = DocumentsContract.getDocumentId(uri);
                    final Uri contentUri = ContentUris.withAppendedId(
                            Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

                    return getDataColumn(context, contentUri, null, null);
                }

                // MediaProvider
                else if (isMediaDocument(uri)) {
                    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]
                    };

                    return getDataColumn(context, contentUri, selection, selectionArgs);
                }
            }
            // MediaStore (and general)
            else if ("content".equalsIgnoreCase(uri.getScheme())) {

                // Return the remote address
                if (isGooglePhotosUri(uri))
                    return uri.getLastPathSegment();

                return getDataColumn(context, uri, null, null);
            }
            // File
            else if ("file".equalsIgnoreCase(uri.getScheme())) {
                return uri.getPath();
            }
        }

        return null;
    }

    /**
     * Get the value of the data column for this Uri. This is useful for
     * MediaStore Uris, and other file-based ContentProviders.
     *
     * @param context The context.
     * @param uri The Uri to query.
     * @param selection (Optional) Filter used in the query.
     * @param selectionArgs (Optional) Selection arguments used in the query.
     * @return The value of the _data column, which is typically a file path.
     */
    public 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 index = cursor.getColumnIndexOrThrow(column);
                return cursor.getString(index);
            }
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return null;
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is ExternalStorageProvider.
     */
    public static boolean isExternalStorageDocument(Uri uri) {
        return "com.android.externalstorage.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is DownloadsProvider.
     */
    public static boolean isDownloadsDocument(Uri uri) {
        return "com.android.providers.downloads.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is MediaProvider.
     */
    public static boolean isMediaDocument(Uri uri) {
        return "com.android.providers.media.documents".equals(uri.getAuthority());
    }

    /**
     * @param uri The Uri to check.
     * @return Whether the Uri authority is Google Photos.
     */
    public static boolean isGooglePhotosUri(Uri uri) {
        return "com.google.android.apps.photos.content".equals(uri.getAuthority());
    }
}

我的问题是，当使用内置文件浏览器浏览文件时，此代码返回null。其他浏览器工作正常。.请帮助我，为什么使用内置文件浏览器时得到 null