在不使用Android活动的情况下访问用户google驱动器

Question

我正在尝试实现一个Android应用，其中该应用将图像上传到用户google驱动器。我成功实现了here给出的快速入门指南。它正在上传图片，但使用android Activity上传图片的所有示例/示例。我经历了Google提供的documentation，但它的耦合程度很低。

是否有任何示例/示例在不使用活动的情况下上传文件，以便以后可以将其转换为后台服务？

我达到了以下几点。现在，此时GoogleSignIn.getLastSignedInAccount返回null，我正在寻找一种解决方案，它选择帐户并获得用户的许可。在google示例中，它似乎在startActivityForResult中执行。我也尝试过寻找它，但没有适用于Android的Drive REST v3示例。

package com.mpathak.drivetesting;

import android.content.Context;
import android.content.IntentSender;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;

import com.google.android.gms.auth.api.signin.GoogleSignIn;
import com.google.android.gms.auth.api.signin.GoogleSignInAccount;
import com.google.android.gms.auth.api.signin.GoogleSignInClient;
import com.google.android.gms.auth.api.signin.GoogleSignInOptions;
import com.google.android.gms.drive.CreateFileActivityOptions;
import com.google.android.gms.drive.Drive;
import com.google.android.gms.drive.DriveClient;
import com.google.android.gms.drive.DriveContents;
import com.google.android.gms.drive.DriveResourceClient;
import com.google.android.gms.drive.MetadataChangeSet;
import com.google.android.gms.tasks.Task;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class DriveSample {
    private GoogleSignInClient mGoogleSignInClient;
    private DriveClient mDriveClient;
    private DriveResourceClient mDriveResourceClient;
    private Context _context;
    private static final String TAG = "drive-Testing";

    public DriveSample(Context context)
    {
        _context = context;
    }

    public void uploadFile()
    {
        GoogleSignInClient GoogleSignInClient = buildGoogleSignInClient();

        mDriveClient = Drive.getDriveClient(_context, GoogleSignIn.getLastSignedInAccount(_context));

        mDriveResourceClient =
                Drive.getDriveResourceClient(_context, GoogleSignIn.getLastSignedInAccount(_context));

        saveFileToDrive();
    }

    private GoogleSignInClient buildGoogleSignInClient() {
        GoogleSignInOptions signInOptions =
                new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
                        .requestScopes(Drive.SCOPE_FILE)
                        .build();
        return GoogleSignIn.getClient(_context, signInOptions);
    }

    private void saveFileToDrive() {
        Log.i(TAG, "Creating new contents.");

        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inSampleSize = 10;

        final Bitmap image = BitmapFactory.decodeFile("/DCIM/Camera/some_image.jpg", options);

        mDriveResourceClient
                .createContents()
                .continueWithTask(
                        task -> createFileIntentSender(task.getResult(), image))
                .addOnFailureListener(
                        e -> Log.w(TAG, "Failed to create new contents.", e));
    }

    private Task<Void> createFileIntentSender(DriveContents driveContents, Bitmap image) {
        Log.i(TAG, "New contents created.");

        OutputStream outputStream = driveContents.getOutputStream();

        ByteArrayOutputStream bitmapStream = new ByteArrayOutputStream();
        image.compress(Bitmap.CompressFormat.PNG, 100, bitmapStream);
        try {
            outputStream.write(bitmapStream.toByteArray());
        } catch (IOException e) {
            Log.w(TAG, "Unable to write file contents.", e);
        }

        MetadataChangeSet metadataChangeSet =
                new MetadataChangeSet.Builder()
                        .setMimeType("image/jpeg")
                        .setTitle("Android Photo.png")
                        .build();

        CreateFileActivityOptions createFileActivityOptions =
                new CreateFileActivityOptions.Builder()
                        .setInitialMetadata(metadataChangeSet)
                        .setInitialDriveContents(driveContents)
                        .build();

        return mDriveClient
                .newCreateFileActivityIntentSender(createFileActivityOptions)
                .continueWith(
                        task -> {
                            return null;
                        });
    }

}