Get a return value from OnPostExecute android

Question

First of all i have to say, i have read this:

How to get the return value from onpostexecute method in android?

And that:

How do I return a boolean from AsyncTask?

With no help, maybe i didn't understand what they were saying. Here is my porblem: i just need to get back the String value which is in my OnPostExecute method. not from doInBackground, i need it from my OnPostExecute.

My code:

 public void max(String build,String cls)
{

    BackgroundTask3 myTask = new BackgroundTask3();
    myTask.execute(build,cls);


    Toast.makeText(getApplicationContext(),"fcur is" + Fcur,Toast.LENGTH_LONG).show();

}

and:

public class BackgroundTask3 extends AsyncTask<String,Void,String>
{

    String capacity_url;
    @Override
    protected void onProgressUpdate(Void... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(String result) {
    String finalValue;
      json_capacity = result;
        finalValue=parseMax();
        Toast.makeText(getApplicationContext(),"finalValue is" + finalValue,Toast.LENGTH_LONG).show();
        super.onPostExecute(result);

    }

    @Override
    protected void onPreExecute() {
        capacity_url = "http://www.skedge.co.il/ANCurrentCapacity.php";
    }

    @Override
    protected String doInBackground(String... params) {
        String cls,build;
        build= params[0];
        cls = params[1];

        try {
            URL url = new URL (capacity_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            OutputStream outputStream = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            String data_string = URLEncoder.encode("Fclass","UTF-8")+"="+URLEncoder.encode(cls,"UTF-8")+"&"+
                    URLEncoder.encode("building","UTF-8")+"="+URLEncoder.encode(build,"UTF-8")+"&"+
                    URLEncoder.encode("hour","UTF-8")+"="+URLEncoder.encode(hour,"UTF-8");
            bufferedWriter.write(data_string);
            bufferedWriter.flush();
            bufferedWriter.close();
            //here is the new
            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream,"UTF-8"));
            StringBuilder stringBuilder = new StringBuilder();
            while ((JSON_STRING = bufferedReader.readLine())!= null)
            {
                stringBuilder.append(JSON_STRING+"\n");
            }
            outputStream.close();
            inputStream.close();
            httpURLConnection.disconnect();
            return stringBuilder.toString().trim();


        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;

    }
}

All i want to do is: assign the value which is in finalValue String inside the OnPostExecute,to the Fcur (public String) which is inside to max function.

Looks very simple but for some reason i can't get it done.

score 2 · Answer 1 · answered Apr 09 '17 at 13:00

Best way to get a callback from background thread is to use interfaces as a callback from AsyncTask for example:

create an interface that can be called in onPostExecute()

public interface ResponseCallback {

    void onRespond();
}

and before calling asynckTask define it like this:

   ResponseCallback callback = new ResponseCallback() {
            @Override
            public void onRespond() {
              //code to be done after calling it from onPostExecute
            }
        };

and pass callback to the constructor of of the asynckTask and call it in onPostExecute

of course you can modify the signature of the interface to what ever you want.

I utilize this also because thinking as interface is the better way to implement responses to asyncTask callback. — Francis Rodrigues, Apr 09 '17 at 13:12
@Yarden Rotem, try this: http://stackoverflow.com/a/13815960/3332734 — Francis Rodrigues, Apr 09 '17 at 13:15

Get a return value from OnPostExecute android

1 Answers1