Android App: Acquire Access Token for Google Drive API - google-drive-api

Question

I am writing an Android (version ICS) app. which uploads data to the Google Drive. The app
uses oauth2 to acquire the access token.
First step: acquire authorization token.
String AUTH_TOKEN_TYPE = "oauth2:https://www.googleapis.com/auth/drive";
// Step 1
accountManager.getAuthToken(
account, // Account retrieved using getAccountsByType("com.google")
AUTH_TOKEN_TYPE, // Auth Token Type
options, // Authenticator-specific options
this, // Your activity
new OnTokenAcquired(), // Callback called when a token is successfully acquired
new Handler(new OnAuthTokenError())); // Callback called if an error occurs
}
private class OnTokenAcquired implements AccountManagerCallback<Bundle> {
#Override
public void run(AccountManagerFuture<Bundle> result) {
// Get the result of the operation from the AccountManagerFuture.
Bundle bundle;
try {
bundle = result.getResult();
authToken = bundle.getString(AccountManager.KEY_AUTHTOKEN);
Log.d(TAG,"authToken:" + authToken);
exchangeToken access = (exchangeToken) new exchangeToken().execute();
} catch (OperationCanceledException e) {
e.printStackTrace();
} catch (AuthenticatorException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
Success. An authorization token is acquired.
Step 2: Exchange authorization token for Access Token.
private class exchangeToken extends AsyncTask<String, Void, Void> {
#Override
protected Void doInBackground(String... params) {
HttpTransport transport = new NetHttpTransport();
JsonFactory jsonFactory = new GsonFactory();
String CLIENT_ID = "999999999999.apps.googleusercontent.com";
String CLIENT_SECRET = "axXXXXXXXXXXXXXXX7";
try { // Step 2: Exchange for an access and refresh token
GoogleTokenResponse authResponse = new GoogleAuthorizationCodeTokenRequest(transport, jsonFactory, CLIENT_ID, CLIENT_SECRET, authToken, CALLBACK_URL).execute();
accessToken = authResponse.getAccessToken();
Log.d("Get Access","Token:" + accessToken);
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
Fail. The LogCat shows the following:
com.google.api.client.auth.oauth2.TokenResponseException: 400 Bad Request
{
"error":"unauthorized_client"
}
I have been able to access "Google Drive" on my Android tablet using the "Drive" app. so
my email account is valid. May be the AUTH_TOKEN_TYPE is incorrect, but the Google Drive
SDK is not clear what it must be. What am I missing?

Answer 1

You do not need to do the second step of exchanging the token. Android grants you an access token directly, it does not grant you an auth code which you would have to exchange for tokens.
This page on the Android documentation explains everything really well.

Answer 2

You know that for using the Drive API your users have to install your app on the Chrome(!) Webstore?
Normally Documents List API is the better choice from Android.