review-google-drive-code

    // Code to download.
    Drive drive = getDriveService(googleSignInAccount);
    com.google.api.services.drive.model.File driveFile = searchFromGoogleDrive(drive);
    File downloadedZipFile = downloadFromAppFolder(drive, driveFile);


    // Code to upload.
    Drive drive = getDriveService(googleSignInAccount);
    com.google.api.services.drive.model.File driveFile = searchFromGoogleDrive(drive);
    uploadToAppFolder(drive, driveFile, zipFile)


    // All Google Drive API related functions.
    private static com.google.api.services.drive.model.File searchFromGoogleDrive(Drive drive) {
        try {
            // TODO: Why "nextPageToken, files(id, name)"?
            // TODO: Why 10?
            Drive.Files.List request = drive.files().list().setSpaces("appDataFolder")
                    .setFields("nextPageToken, files(id, name)")
                    .setPageSize(10);

            do {
                FileList fileList = request.execute();

                com.google.api.services.drive.model.File file = null;

                for (com.google.api.services.drive.model.File f : fileList.getFiles()) {
                    if (isNullOrEmpty(f.getId())) {
                        continue;
                    }

                    file = f;

                    break;
                }

                if (file != null) {
                    return file;
                }

                request.setPageToken(fileList.getNextPageToken());
            } while (request.getPageToken() != null && request.getPageToken().length() > 0);
        }  catch (UserRecoverableAuthIOException e) {
            // TODO: We should have a better way to handle UserRecoverableAuthIOException.
            
            Log.e(TAG, "", e);
            return null;
        } catch (IOException e) {
            Log.e(TAG, "", e);
            return null;
        }
        return null;
    }

    private static File downloadFromAppFolder(Drive drive, com.google.api.services.drive.model.File file) {
        try {
            java.io.File outputFile = null;
            OutputStream outputStream = null;

            try {
                outputFile = File.createTempFile(getWeNoteUUID(), ".zip");
                outputFile.deleteOnExit();
                outputStream = new FileOutputStream(outputFile);

                drive.files().get(file.getId())
                        .executeMediaAndDownloadTo(outputStream);
            } catch (IOException ex) {
                Log.e(TAG, "", ex);
            } finally {
                close(outputStream);
            }

            return outputFile;
        } catch (Exception e) {
            Log.e(TAG, "", e);
        }

        return null;
    }
    
    private static boolean uploadToAppFolder(Drive drive, com.google.api.services.drive.model.File existingDriveFile, java.io.File file) {
        com.google.api.services.drive.model.File driveFile = new com.google.api.services.drive.model.File();
        driveFile.setName(getWeNoteZipFileTitle());
        driveFile.setParents(Collections.singletonList(APP_DATA_FOLDER));
        driveFile.setMimeType(APPLICATION_ZIP);

        FileContent fileContent = new FileContent(APPLICATION_ZIP, file);

        try {
            if (existingDriveFile != null) {
                // OVERWRITE EXISTING FILE
                
                drive.files().update(existingDriveFile.getId(), driveFile, fileContent);
            } else {
                // CREATING NEW FILE

                drive.files().create(driveFile, fileContent)
                        .execute();
            }
        } catch (IOException e) {
            Log.e(TAG, "", e);
            return false;
        }
        return true;
    }