Android : Android. Can't list files in a folder that was opened by Drive.DriveApi.newOpenFileActivityBuilder()

Using code at https://github.com/googledrive/android-demos, I opened a folder from my app with PickFolderWithOpenerActivity.java;

@Override
public void onConnected(Bundle connectionHint) {
    super.onConnected(connectionHint);
    IntentSender intentSender = Drive.DriveApi
            .newOpenFileActivityBuilder()
            .setMimeType(new String[] { DriveFolder.MIME_TYPE })
            .build(getGoogleApiClient());

The driveId of the choosen folder is returned with

DriveId driveId = (DriveId) data.getParcelableExtra(OpenFileActivityBuilder.EXTRA_RESPONSE_DRIVE_ID);

I use the same driveId in ListFilesInFolderActivity.java to get the list of files in the choosen folder. This is the code

Drive.DriveApi.fetchDriveId(getGoogleApiClient(), EXISTING_FOLDER_ID)
            .setResultCallback(idCallback);

However, access fails with this message -

"Cannot find DriveId. Are you authorized to view this file?"

The Google Drive API for android docs say -

The Google Drive Android API currently only supports drive.file and drive.appfolder authorization scopes.

And authorization scope docs say

scope drive.file means Per-file access to files created or opened by the app

Still the above doesn't works. What am I missing?