Android Programming: Google Service/App Authentication

December 23rd, 2008

While many of the Google applications already have Android-based ports, some of the more “specialty apps” such as AdSense don’t have a mobile interface. Luckily, the Google API allows for an easy login method using an HTTP Post request. One of our current applications, SimpleAdMonitor, uses this method to download an AdSense user’s daily and all time totals.

While the solution is fairly easy to implement, the actual POST request appears to run quite slowly, at least over the Android emulator and somewhat on the device as well.

The first step to generating an authorized session is to post the user’s login details to the Google ServiceLogin:

   1: String login = "https://www.google.com/accounts/ServiceLoginAuth?service=adsense&hl=en-US&ltmpl=login&ifr=true&passive=true&rm=hide&nui=3&alwf=true&continue=https%3A%2F%2Fwww.google.com%2Fadsense%2Fgaiaauth&followup=https%3A%2F%2Fwww.google.com%2Fadsense%2Fgaiaauth";
   2: DefaultHttpClient client = new DefaultHttpClient();
   3: String websiteData = null;
   4: URI uri = new URI(login);
   5: HttpPost method = new HttpPost(uri);
   6: method.addHeader("User-Agent", "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.8.1.10) Gecko/20071115 Firefox/2.0.0.10");
   7: method.addHeader("Pragma", "no-cache");
   8: method.addHeader("Content-Type", "application/x-www-form-urlencoded");

On line 1, the address specifies a Google service to authorize against. This service can be changed if you need to access some other application. Once this request is formed, the user’s login information can be added using a NameValuePair list. These are then set on the HttpPost method using setEntity:

   1: List <NameValuePair> loginInfo = new ArrayList <NameValuePair>();
   2: loginInfo.add(new BasicNameValuePair("Email", username));
   3: loginInfo.add(new BasicNameValuePair("Passwd", password));
   4: loginInfo.add(new BasicNameValuePair("null", "Sign+in"));
   5: HttpEntity entity = new UrlEncodedFormEntity(nvps, HTTP.UTF_8);
   6:
   7: method.setEntity(entity);
   8: HttpResponse res = client.execute(method);

One item to note on line 3 is that the param used for the password is “Passwd”. Once this data is posted, the server will return a response that should be evaluated for a correct login. If the login is valid, the page should respond with a link to a redirect page that needs to again be posted to:

   1: String login2 = "https://www.google.com/accounts/CheckCookie?continue=https%3A%2F%2Fwww.google.com%2Fadsense%2Fgaiaauth&followup=https%3A%2F%2Fwww.google.com%2Fadsense%2Fgaiaauth&hl=en-US&service=adsense&ltmpl=login&chtml=LoginDoneHtml";
   2: method.setURI(new URI(login2));
   3: res = client.execute(method);

At this point, the server should respond with the data from the redirect URL, in this case, the main AdSense page. Further requests can now be made to the server using the same method without needing to re-authorize the user. As I mentioned previously, there are some latency issues with this method that I haven’t quite sorted out yet. The lag isn’t horrible, but is fairly significant when waiting for two fairly small pieces of data. Some additional digging will hopefully find out what is causing the delay and how to improve it.

Android Programming: DefaultHttpClient GET Request

December 16th, 2008

This article will briefly describe the method to form and receive an HTTP GET request in Android. The first code snippet listed below shows how to form the request and receive the data back from the server.  The second shows a function that can be used to read the InputStream and save it to a string. The entire process isn’t very difficult, but can be a bit confusing the first time you try to piece it together. The code below still requires some additional code to fail more elegantly in case of a broken internet connection, website error, etc., but should copy/paste pretty easily into applications.

   1: public String getUrlData(String url) {
   2:     String websiteData = null;
   3:     try {
   4:         DefaultHttpClient client = new DefaultHttpClient();
   5:         URI uri = new URI(url);
   6:         HttpGet method = new HttpGet(uri);
   7:         HttpResponse res = client.execute(method);
   8:         InputStream data = res.getEntity().getContent();
   9:         websiteData = generateString(data);
  10:     } catch (ClientProtocolException e) {
  11:         // TODO Auto-generated catch block
  12:         e.printStackTrace();
  13:     } catch (IOException e) {
  14:         // TODO Auto-generated catch block
  15:         e.printStackTrace();
  16:     } catch (URISyntaxException e) {
  17:         // TODO Auto-generated catch block
  18:         e.printStackTrace();
  19:     }
  20:
  21:     return websiteData;
  22: }
   1: public String generateString(InputStream stream) {
   2:     InputStreamReader reader = new InputStreamReader(stream);
   3:     BufferedReader buffer = new BufferedReader(reader);
   4:     StringBuilder sb = new StringBuilder();
   5:
   6:     try {
   7:         String cur;
   8:         while ((cur = buffer.readLine()) != null) {
   9:             sb.append(cur + "\n");
  10:         }
  11:     } catch (IOException e) {
  12:         // TODO Auto-generated catch block
  13:         e.printStackTrace();
  14:     }
  15:
  16:     try {
  17:         stream.close();
  18:     } catch (IOException e) {
  19:         // TODO Auto-generated catch block
  20:         e.printStackTrace();
  21:     }
  22:     return sb.toString();
  23: }