Using thread and asyncTask - multithreading

Question

I am pretty new on android and i have problem with asyncTask and threads.
how can i use AsyncTask in this code?
when i using like this productIdList comes null.That's why i want to use AsyncTask. I think using AsyncTask could work.
thanks in advance.
public ArrayList<String> getProductData() {
final ArrayList<String> productIdList = new ArrayList<String>();
new Thread(new Runnable() {
public void run() {
HttpClient httpclient= new DefaultHttpClient();
GeneralConstans GC = new GeneralConstans();
// Products will be stated in memory
HttpPost httpget = new HttpPost(GC.UrlConstants);
HttpResponse response;
String result = null;
try {
HttpContext ctx = new BasicHttpContext();
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
2);
httpget.setEntity(new UrlEncodedFormEntity(nameValuePairs,
"UTF-8"));
response = httpclient.execute(httpget, ctx);
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
result = EntityUtils.toString(resEntity);
JSONArray arr = new JSONArray(result);
Gson gson = new Gson();
if (arr.length() > 0) {
for (int j = 0; j < arr.length(); j++) {
Product p = gson.fromJson(arr.getString(j),
Product.class);
productIdList.add(p.toString());
}
}
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (SocketException e) {
/*if (checkAbortStatus(e.getMessage()) == true) {
handler.sendEmptyMessage(0);
}*/
} catch (IOException e) {
/*if (checkAbortStatus(e.getMessage()) == true) {
handler.sendEmptyMessage(0);
}*/
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
}
private Handler handler = new Handler() {
#Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
}
};
}).start();
return productIdList;

Answer 1

A Async task implicitly moves methods and commands away from the main thread, as the MAIN thread should run all tasks.
create a new class,
public class <NAME OF CLASS> extends AsyncTask<Void, String, String>
the extends part basically extends (inherits in c#) taking in some parameters, these parameters relate to the 3 overrided methods you are going to utilise.
onPreExecute - this is a kind of pre doing things method, i personally dont need it code i've written (i'm still new to android myself)
onDoInBackgound - this is the main part of the AsyncTask, this is where all your method will go, this is where all the logic will happen. This is exactly what it says on the tin, it does everything in the background on the other thread.
onPostExecute - when the onDoInBackground is finished it will run the OnPostExecute method, i usually have a String return on the onDoInBackgroun method, which ensures it progresses to the onPostExecute as i found sometimes without it it didnt quite progress.
then in the postExecute method you tell it what you want to do once all the logic is done, e.g you could have a listener on the Main thread in which you call that listener from the AysncTask i.e listener.onSuccess(results) in the postExecute Method, which will return you to the original thread.
Hope this helps