How to use Google Drive SDK in Android project with hardcoded credentials

Ok, I've found solution for my problem.

Of course my app is an Android one, I dont'n want make user to log in/use any credentials to connect to my Drive, and lastly I can manipulate files using default Drive web app.

1. Seps need to be taken: Create service account as in this example.
2. Download private key API Access site and put it eg. in assets folder.
3. Download and import these libraries:
   • google-api-client-1.13.2-beta.jar
   • google-api-client-android-1.13.2-beta.jar
   • google-api-services-drive-v2-rev60-1.13.2-beta.jar
   • google-http-client-1.13.1-beta.jar
   • google-http-client-android-1.13.1-beta.jar
   • google-http-client-gson-1.13.1-beta.jar
   • google-http-client-jackson2-1.13.1-beta.jar
   • google-oauth-client-1.13.1-beta.jar
   • gson-2.1.jar
   • guava-jdk5-13.0.jar
   • jackson-core-2.0.5.jar
   • jsr305-1.3.9.jar

4. Implement Drive service getter:

   public Drive getDriveService() throws GeneralSecurityException, IOException, URISyntaxException {
       HttpTransport httpTransport = new NetHttpTransport();
       JacksonFactory jsonFactory = new JacksonFactory();
       GoogleCredential credential = new GoogleCredential.Builder()
           .setTransport(httpTransport)
           .setJsonFactory(jsonFactory)
           .setServiceAccountId(G_SERVICE_EMAIL)
           .setServiceAccountScopes(DriveScopes.DRIVE)
           .setServiceAccountPrivateKeyFromP12File(PKC_12_FILE)
           .build();
       Drive service = new Drive.Builder(httpTransport, jsonFactory, null)
           .setHttpRequestInitializer(credential)
           .build();
       return service;
   }
   

   Where G_SERVICE_EMAIL is email address from API Access site and PKC_12_FILE is previously downloaded private key.

5. Allow your service to access folder from your Drive: in sharing options of the folder in Drive app allow user with email: G_SERVICE_EMAIL read/write access.

   PKC FILE INTEGRATION

   private File getTempPkc12File() throws IOException {
       InputStream pkc12Stream = getAssets().open("this-is-your-unique-hash-privatekey.p12");
       File tempPkc12File = File.createTempFile("temp_pkc12_file", "p12");
       OutputStream tempFileStream = new FileOutputStream(tempPkc12File);
   
       int read = 0;
       byte[] bytes = new byte[1024];
       while ((read = pkc12Stream.read(bytes)) != -1) {
           tempFileStream.write(bytes, 0, read);
       }
       return tempPkc12File;
   }