This is a basic Android demo app to access Google Drive using Googleapis.

GCP project creation

To access Google Drive, you will need to setup a Google Cloud Platform project, using your developer account. With it, any user will be able to acess their own GDrive files.

In GCP Console, go to "Api & Services" / "OAUTH CONSENT SCREEN":

• app name: TestGDrive_gcp
• User support email: ...
• User type: internal vs external - it only allows me to choose EXTERNAL
• App domain: nothing
• Scopes? nothing ("Scopes express the permissions you request users to authorize for your app and allow your project to access specific types of private user data from their Google Account.")
• Test users: Since this is a TEST app, you need to give the users that will be able to use it

Now go to "Api & Services" / CREATE CREDENCIAL, and choose Create a credential / OAUTH CLIENT ID:

• app type: android
• name: Android client 1
• package name: your android package
• SHA1 - you can get it from Android Studio. See https://stackoverflow.com/questions/27609442/how-to-get-the-sha-1-fingerprint-certificate-in-android-studio-for-debug-mode

OAuth client created! He will give the client ID, but we don't need to use it

Finally, go to ENABLE APIS AND SERVICES, and Enable the Google Drive API - "The Google Drive API allows clients to access resources from Google Drive."

Android project

These are the steps:

• Get required permissions, and create Drive and Credential objects. See initDrive function
• Launch an Intent to allow the user to choose an account. A android system dialog will show up. See chooseAccountLauncher.
• Make Drive api calls
• If we get an UserRecoverableAuthIOException, we get the intent property from the exception object, and launch it. This should happen the first time the user uses the app. A android system dialog will show up, asking the user to allow our GCP app to access his GDrive data. See userRecoverableAuthLauncher

For more information about the Google Drive API (This is a Java API, not Android specific): https://developers.google.com/drive/api/guides/about-sdk

Note: I couldn't find where the trick of getting the Intent from the auth exception is documented. I learned it from other examples and posts I found online.

About getting the GDrive root folder

I tried several queries, none worked:

  q ="'' in parents"  // "File not found: ."
  q ="null in parents"  // bad request "Invalid Value"
  q = "name = 'My files'" // gives 0 results... but my root folder is named like this!
  q = "'drive' in parents"  -- error
  q="not parents" // Unknown Error.
  q="parents = null" // invalid value
  etc

The only solution I found was to get a random file, and follow its ancestors until getting a folder with null parent. That should be the top folder. But this process involves several google api calls. And I don't know if it is guaranteed to always work.

See here: https://stackoverflow.com/questions/44090344/retrieving-top-level-files-in-shared-with-me-from-google-drive-v3-java-api/77203855#77203855