Android OAuth: Exception on retrieveAccessToken()

Question

I'm setting up OAuth for my Android app. To test it I did the following: Added signpost-core-1.2.1.1.jar and signpost-commonshttp4-1.2.1.1.jar to my project, added the variables "CommonsHttpOAuthConsumer consumer" and "CommonsHttpOAuthProvider provider" and did the following when the button is clicked:

consumer = new CommonsHttpOAuthConsumer("xxx", "yyy");
provider = new CommonsHttpOAuthProvider("https://api.twitter.com/oauth/request_token", 
                    "https://api.twitter.com/oauth/access_token", 
                    "https://api.twitter.com/oauth/authorize");

oauthUrl = provider.retrieveRequestToken(consumer, "myapp://twitterOauth");
persistOAuthData();
this.startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(oauthUrl)));

persistOAuthData() does the following:

protected void persistOAuthData()
{
    try
    {
        FileOutputStream providerFOS = this.openFileOutput("provider.dat", MODE_PRIVATE);
        ObjectOutputStream providerOOS = new ObjectOutputStream(providerFOS);
        providerOOS.writeObject(this.provider);
        providerOOS.close();

        FileOutputStream consumerFOS = this.openFileOutput("consumer.dat", MODE_PRIVATE);
        ObjectOutputStream consumerOOS = new ObjectOutputStream(consumerFOS);
        consumerOOS.writeObject(this.consumer);
        consumerOOS.close();
    }
    catch (Exception e) { }
}

So, the consumer and the provider are saved before opening the browser, like described here.

In the onResume() method I load the provider and consumer data and do the following:

    Uri uri = this.getIntent().getData();
    if (uri != null && uri.getScheme().equals("myapp") && uri.getHost().equals("twitterOauth"))
    {
        verifier = uri.getQueryParameter(oauth.signpost.OAuth.OAUTH_VERIFIER);
        if (!verifier.equals(""))
        {
            loadOauthData();
            try
            {
                provider.retrieveAccessToken(consumer, verifier);
            }
            catch (OAuthMessageSignerException e) {
                e.printStackTrace();
            } catch (OAuthNotAuthorizedException e) {
                e.printStackTrace();
            } catch (OAuthExpectationFailedException e) {
                e.printStackTrace();
            } catch (OAuthCommunicationException e) {
                e.printStackTrace();
            }            
        }
    }

So, what works: 1) I do get a requestToken and a requestSecret. 2) I do get the oauthUrl. 3) I am directed to the browser page to authorize my app 4) I am getting redirected to my app. 5) I do get the verifier. But calling retrieveAccessToken(consumer, verifier) fails with an OAuthCommunicationException saying "Communication with the service provider failed: null".

Does anyone know what might be the reason? Some people seem to have problems getting the requestToken, but that just works fine. I wonder if it might be a problem that my app has also included the apache-mime4j-0.6.jar and httpmime-4.0.1.jar which I need for multipart upload.

Answer 1

Okay, I figured it out. Maybe this is helpful to others:

First of all, you do not need to save the whole consumer and provider object. All you need to do is store the requestToken and the requestSecret. Luckily, those are Strings, so you don't need to write them to disk or anything. Just store them in the sharedPreferences or something like that.

Now, when you get redirected by the browser and your onResume() method is called, just do the following:

//The consumer object was lost because the browser got into foreground, need to instantiate it again with your apps token and secret.
consumer = new CommonsHttpOAuthConsumer("xxx", "yyy"); 

//Set the requestToken and the tokenSecret that you got earlier by calling retrieveRequestToken.
consumer.setTokenWithSecret(requestToken, tokenSecret);

//The provider object is lost, too, so instantiate it again.
provider = new CommonsHttpOAuthProvider("https://api.twitter.com/oauth/request_token", 
                                "https://api.twitter.com/oauth/access_token", 
                                "https://api.twitter.com/oauth/authorize");     
//Now that's really important. Because you don't perform the retrieveRequestToken method at this moment, the OAuth method is not detected automatically (there is no communication with Twitter). So, the default is 1.0 which is wrong because the initial request was performed with 1.0a.
provider.setOAuth10a(true);

provider.retrieveAccessToken(consumer, verifier);

That's it, you can receive the token and the secret with getToken() and getTokenSecret(), now.