How do i return a result from a async task [duplicate]

Question

I have been using async tasks to hit a web server and updating controls using the result. This has drawbacks, namely it makes the async methods specific to controls and stops me using the returned string again.

How do i return the resulting string from a async call onPostExecute? How do i call it? I cant seem to get my code able to do that. There should be no issues with threading as i have a dialog that freezes the UI until job is done.

My typical asyncTask code is as follows

class GetDataFromServer extends AsyncTask<String, String, String>
{
     * */
    // Progress Dialog
    private ProgressDialog qDialog;
    private Context context;
    private String dialogString;
    private ArrayList<String[]> newLoginResult;

    // JSON parser class
    String url_newGame ="http://xxxxxx.php";

    public myAsyncMethos(String dialogMessage, Context con)
    {
        this.qDialog =  new ProgressDialog(con);
        this.dialogString = dialogMessage;
        this.context = con;
    }

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
        qDialog = new ProgressDialog(this.context);
        qDialog.setMessage(this.dialogString);
        qDialog.setIndeterminate(false);
        qDialog.setCancelable(false);
        qDialog.show();
    }

    @Override
    protected JSONObject doInBackground(String... args)
    {
        //MAKE SERVER CALL and cast to JSONOBject

        return jsonNewUser;
    }

    public void onPostExecute(JSONObject jsonString)
    {

         // dismiss the dialog after getting response
        qDialog.dismiss();
//I WANT TO RETURN A STRING HERE BUT KEEP GETTING SYNTAX ERRORS BEFORE RUNTIME


    }
}

Answer 1

I would personally add a callback to your class, then once onPostExecute is run, fire off your callback to the listener on the main class.

class GetDataFromServer extends AsyncTask<String, String,JSONObject>
{
    // Progress Dialog
    private ProgressDialog qDialog;
    private Context context;
    private String dialogString;
    private ArrayList<String[]> newLoginResult;
    private InformComplete myCallback;

    public GetDataFromServer(String dialogMessage, Context con,InformComplete callback)
    {
        this.qDialog =  new ProgressDialog(con);
        this.dialogString = dialogMessage;
        this.context = con;
        this.myCallback=callback;
    }

    @Override
    protected void onPreExecute()
    {
        // set up your dialog
    }

    @Override
    protected JSONObject doInBackground(String... args)
    {
        JSONObject jsonNewUser=new JSONObject();
        return jsonNewUser;
    }

    public void onPostExecute(JSONObject jsonString)
    {
        qDialog.dismiss();
        myCallback.PostData(jsonString);
    }
    public interface InformComplete
    {
        public void PostData(JSONObject result);
    }
}

Then from your calling class, you'd have something like this...

    private void callTheAsyncThing
    {
        GetDataFromServer gds=new GetDataFromServer("please wait", this, letMeKnow);
        gds.execute(params);
    }

    private InformComplete letMeKnow=new InformComplete()
    {
        public void PostData(JSONObject result)
        {
            // we now have the data in the calling class
        }
    };

Answer 2

You can't return a value in methods from AsynTask cause it used to return a void element. So, you can instance global var foe example, and set the value to it. Like... `

class GetDataFromServer extends AsyncTask<String, String, String>
{
     * */
    // Progress Dialog
    private ProgressDialog qDialog;
    private Context context;
    private String dialogString;
    private ArrayList<String[]> newLoginResult;
    private String value;

    // JSON parser class
    String url_newGame ="http://xxxxxx.php";

    public myAsyncMethos(String dialogMessage, Context con)
    {
        this.qDialog =  new ProgressDialog(con);
        this.dialogString = dialogMessage;
        this.context = con;
    }

    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
        qDialog = new ProgressDialog(this.context);
        qDialog.setMessage(this.dialogString);
        qDialog.setIndeterminate(false);
        qDialog.setCancelable(false);
        qDialog.show();
    }

    @Override
    protected JSONObject doInBackground(String... args)
    {
        //MAKE SERVER CALL and cast to JSONOBject

        return jsonNewUser;
    }

    public void onPostExecute(JSONObject jsonString)
    {

         // dismiss the dialog after getting response
        qDialog.dismiss();
        value = "Whatever you want";
    }
    public void setValue(String value){
         this.value=value;
    }
    public String getValue(){
         return this.value;
    }
}`

And then use it. There is one way to return something. Btw you can't change return.