Android - Ruby on Rails app, setup and HttpClient hello world

OK, onto the initial post for my foray into Android and Ruby on Rails.  This basic application assumes you have Ruby on Rails 2.0 installed using MySQL and the 1.0 Android SDK.

I am by no means an expert in Ruby on Rails, and am still learning the Android API and SDK, so if any of you ninjas/rockstars/experts see something that needs correction or a better way of doing things, I’d greatly appreciate the tips.

Other posts on this subject include:

Part 2- SAX Parsing

Part 3 - Using Android Cursors

First the Ruby on Rails server.  We are going with a basic, “headless”, server.  A no frills user interface.  We are interested in the REST calls and returning XML from the controller.  To setup the server we’ll make a new RonR project which I’ve decided to name Phobos, there’s something about moons for project names.

> rails phobos -d mysql
> cd phobos/
> ruby script/server

Don’t forget the MySQL db.

> mysqladmin -u root create phobos_development

A scaffold is added for Projects, this will give us enough structure to get going.

> ruby script/generate scaffold Project name:string
> rake db:migrate

If you point your browser to http://localhost:3000/projects you should be able to create a couple new projects.  Let’s go with ‘Paint House’, and ‘Plan Xmas’ for our projects so later outputs will match up.

Onto the Android project.  I’m assuming you know how to setup an Android project in Eclipse.  Again, I used Phobos as the project name and com.mgm.phobos as the package.

Imports and bare bones Android Activity

package com.mgm.phobos;import java.io.IOException;

import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

public class Phobos extends Activity
{
  TextView tv;

  @Override
  public void onCreate(Bundle savedInstanceState)
  {
    super.onCreate(savedInstanceState);
    retreiveProjects();
  }

Just want to prove that I can get to the projects via the REST call to the Phobos Ruby on Rails server. I had to fiddle around with the proper address in my URL, localhost and 127.0.0.1 should not be used because that refers to the local address on the phone. I used ifconfig (on my Mac) to determine my machines IP address.

  private void retreiveProjects()
  {
    HttpClient httpClient = new DefaultHttpClient();
    try
    {
      String url = "http://10.0.1.2:3000/projects?format=xml";
      Log.d( "phobos", "performing get " + url );

      HttpGet method = new HttpGet( new URI(url) );
      HttpResponse response = httpClient.execute(method);
      if ( response != null )
      {
        Log.i( "phobos", "received " + getResponse(response.getEntity()) );
      }
      else
      {
        Log.i( "phobos", "got a null response" );
      }
    } catch (IOException e) {
      Log.e( "ouch", "!!! IOException " + e.getMessage() );
    } catch (URISyntaxException e) {
      Log.e( "ouch", "!!! URISyntaxException " + e.getMessage() );
    }
  }

Simply get the response contents and output them to Androids log file, don’t forget to use ‘adb logcat’ from the tools directory of the Android SDK directory to view the logs. This simply proves that everything is working properly.

  private String getResponse( HttpEntity entity )
  {
    String response = "";

    try
    {
      int length = ( int ) entity.getContentLength();
      StringBuffer sb = new StringBuffer( length );
      InputStreamReader isr = new InputStreamReader( entity.getContent(), "UTF-8" );
      char buff[] = new char[length];
      int cnt;
      while ( ( cnt = isr.read( buff, 0, length - 1 ) ) > 0 )
      {
        sb.append( buff, 0, cnt );
      }

        response = sb.toString();
        isr.close();
    } catch ( IOException ioe ) {
      ioe.printStackTrace();
    }

    return response;
  }
}

The output I get from the Android log files is

D/phobos  (  524): performing get http://10.0.1.2:3000/projects?format=xml
I/phobos  (  524): received
I/phobos  (  524): <projects type="array">
I/phobos  (  524): <project>
I/phobos  (  524):     <created-at type="datetime">2008-10-01T21:06:51-07:00</created-at>
I/phobos  (  524):     <id type="integer">1</id>
I/phobos  (  524):     <name>Paint House</name>
I/phobos  (  524):     <updated-at type="datetime">2008-10-01T21:06:51-07:00</updated-at>
I/phobos  (  524):   </project>
I/phobos  (  524):  <project>
I/phobos  (  524):     <created-at type="datetime">2008-10-01T21:06:59-07:00</created-at>
I/phobos  (  524):     <id type="integer">2</id>
I/phobos  (  524):     <name>Plan Xmas</name>
I/phobos  (  524):     <updated-at type="datetime">2008-10-01T21:06:59-07:00</updated-at>
I/phobos  (  524):   </project>
I/phobos  (  524):

That should do it for now, at least we’ve proven that’s it’s pretty easy to setup the Ruby on Rails server and Android client then with the scaffolding in Rails create a simple resource and access it via the REST interface using the HTTPClient API from Android.

Got any ideas about what I can do better?  I’m all ears!! Stay tuned to the next installment, hopefully I’ll be as good as this one and get it out soon.