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Passing arguments to AsyncTask, and returning results

Asked 2010-11-16T15:14:42.343
38

I have an application that does some long calculations, and I would like to show a progress dialog while this is done. So far I have found that I could do this with threads/handlers, but didn't work, and then I found out about the AsyncTask.

In my application I use maps with markers on it, and I have implemented the onTap function to call a method that I have defined. The method creates a dialog with Yes/No buttons, and I would like to call an AsyncTask if Yes is clicked. My question is how to pass an ArrayList<String> to the AsyncTask (and work with it there), and how to get back a new ArrayList<String> like a result from the AsyncTask?

The code of the method looks like this:

String curloc = current.toString();
String itemdesc = item.mDescription;

ArrayList<String> passing = new ArrayList<String>();
passing.add(itemdesc);
passing.add(curloc);

ArrayList<String> result = new ArrayList<String>();

new calc_stanica().execute(passing,result);

String minim = result.get(0);
int min = Integer.parseInt(minim);

String glons = result.get(1);
String glats = result.get(2);

double glon = Double.parseDouble(glons);
double glat = Double.parseDouble(glats);

GeoPoint g = new GeoPoint(glon, glat);
String korisni_linii = result.get(3);

So, as you see, I would like to send the string array list "passing" to the AsyncTask, and to get the "result" string array list back from it. And the calc_stanica AssycTask class looks like this:

public class calc_stanica extends AsyncTask<ArrayList<String>, Void, ArrayList<String>> {
    ProgressDialog dialog;

    @Override
    protected void onPreExecute() {
        dialog = new ProgressDialog(baraj_mapa.this);
        dialog.setTitle("Calculating...");
        dialog.setMessage("Please wait...");
        dialog.setInde
android return android-asynctask progressdialog
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1 Answer

4

I sort of agree with leander on this one.

call:

new calc_stanica().execute(stringList.toArray(new String[stringList.size()]));

task:

public class calc_stanica extends AsyncTask<String, Void, ArrayList<String>> {
        @Override
        protected ArrayList<String> doInBackground(String... args) {
           ...
        }

        @Override
        protected void onPostExecute(ArrayList<String> result) {
           ... //do something with the result list here
        }
}

Or you could just make the result list a class parameter and replace the ArrayList with a boolean (success/failure);

public class calc_stanica extends AsyncTask<String, Void, Boolean> {
        private List<String> resultList;

        @Override
        protected boolean doInBackground(String... args) {
           ...
        }

        @Override
        protected void onPostExecute(boolean success) {
           ... //if successfull, do something with the result list here
        }
}
answered 2012-10-30T11:45:12.203

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