shouldOverrideUrlLoading.java

            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String authorizationUrl) {
                //This method will be called when the Auth proccess redirect to our RedirectUri.
                //We will check the url looking for our RedirectUri.
                if (authorizationUrl.startsWith(REDIRECT_URI)) {
                    Log.i("Authorize", "");
                    Uri uri = Uri.parse(authorizationUrl);
                    //We take from the url the authorizationToken and the state token. We have to check that the state token returned by the Service is the same we sent.
                    //If not, that means the request may be a result of CSRF and must be rejected.
                    String stateToken = uri.getQueryParameter(STATE_PARAM);
                    if (stateToken == null || !stateToken.equals(STATE)) {
                        Log.e("Authorize", "State token doesn't match");
                        return true;
                    }

                    //If the user doesn't allow authorization to our application, the authorizationToken Will be null.
                    String authorizationToken = uri.getQueryParameter(RESPONSE_TYPE_VALUE);
                    if (authorizationToken == null) {
                        Log.i("Authorize", "The user doesn't allow authorization.");
                        return true;
                    }
                    Log.i("Authorize", "Auth token received: " + authorizationToken);

                    //Generate URL for requesting Access Token
                    String accessTokenUrl = getAccessTokenUrl(authorizationToken);
                    //We make the request in a AsyncTask
                    new PostRequestAsyncTask().execute(accessTokenUrl);

                } else {
                    //Default behaviour
                    Log.i("Authorize", "Redirecting to: " + authorizationUrl);
                    webView.loadUrl(authorizationUrl);
                }
                return true;
            }
        });
        String authUrl = getAuthorizationUrl();
        Log.i("Authorize", "Loading Auth Url: " + authUrl);
        webView.loadUrl(authUrl);
    }