String driveId;
public String search(String title) {
    driveId = "";
    Query query = new Query.Builder().addFilter(Filters.eq(SearchableField.TITLE, title)).build();
    Drive.DriveApi.query(mGoogleApiClient, query).setResultCallback(new ResultCallback<DriveApi.MetadataBufferResult>() {
        @Override
        public void onResult(DriveApi.MetadataBufferResult metadataBufferResult) {
            if (metadataBufferResult.getStatus().isSuccess()) {
                MetadataBuffer mdb = metadataBufferResult.getMetadataBuffer();
                for (Metadata metadata : mdb) {
                    if (metadata == null || !metadata.isDataValid() || metadata.isTrashed())
                        continue;                       
                    driveId = metadata.getDriveId().encodeToString();

                }
            }
        }
    });
    return driveId;
}