Si quieres jugar haciendo operaciones REST con JSON en Android, y no tienes nada hecho, esto te puede servir de ayuda.
package packageName_00.PackageName_01;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.HttpPut;
import org.apache.http.client.methods.HttpDelete;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.HttpConnectionParams;
import org.json.JSONObject;
import android.util.Log;
public class RestClient {
public interface RequestCallback {
public void onError(Throwable exception);
public void onResponseReceived(HttpResponse response);
}
public static void doGet(final String url, final RequestCallback callback) {
Log.i("doGet", " - url: " + url);
final HttpClient httpClient = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(httpClient.getParams(), 10000);
Thread thread = new Thread(){
public void run() {
HttpGet httpget = new HttpGet(url);
HttpResponse response;
try {
response = httpClient.execute(httpget);
callback.onResponseReceived(response);
} catch (Exception ex) {
callback.onError(ex);
}
}
};
thread.start();
}
public static void doPost (final String url,final JSONObject json, final RequestCallback callback) {
Log.i("doPost a url: " + url, "- JSON: " + json.toString());
final HttpClient httpClient = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(httpClient.getParams(), 10000);
Thread thread = new Thread(){
public void run() {
HttpPost httpPost = new HttpPost(url);
httpPost.addHeader("Accept", "application/json");
httpPost.addHeader("Content-Type", "application/json");
try {
StringEntity entity = new StringEntity(json.toString(), "UTF-8");
entity.setContentType("application/json");
httpPost.setEntity(entity);
// execute is a blocking call, it's best to call this code in a thread separate from the ui's
HttpResponse response = httpClient.execute(httpPost);
callback.onResponseReceived(response);
}
catch (Exception ex) {
callback.onError(ex);
}
}
};
thread.start();
}
public static void doPut (final String url,final JSONObject json,final RequestCallback callback) {
Log.i("doPut a url: " + url, "- JSON: " + json.toString());
final HttpClient httpClient = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(httpClient.getParams(), 10000);
Thread thread = new Thread(){
public void run() {
HttpPut httpPut = new HttpPut(url);
httpPut.addHeader("Accept", "application/json");
httpPut.addHeader("Content-Type", "application/json");
try {
StringEntity entity = new StringEntity(json.toString(), "UTF-8");
entity.setContentType("application/json");
httpPut.setEntity(entity);
HttpResponse response = httpClient.execute(httpPut);
callback.onResponseReceived(response);
}
catch (Exception ex) {
callback.onError(ex);
}
}
};
thread.start();
}
public static void doDelete (final String url, final RequestCallback callback) {
Log.i("doDelete" , " - url: " + url);
final HttpClient httpClient = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(httpClient.getParams(), 10000);
Thread thread = new Thread(){
public void run() {
HttpDelete httpDelete = new HttpDelete(url);
httpDelete.addHeader("Accept", "application/json");
try {
HttpResponse response = httpClient.execute(httpDelete);
callback.onResponseReceived(response);
}
catch (Exception ex) {
callback.onError(ex);
}
}
};
thread.start();
}
}
Para hacer consultas desde el emulador a un servidor en la propia máquina, esto es, una consulta ‘localhost’, debes usar la IP 10.0.2.2
. Hay varias cosas que con Groovy quedarían mucho mas elegantes, pero no hace falta saber utilizar 
