AsyncTask：如何从doInBackground返回HashMap？

Question

I am currently doing a project on android and when I am testing the function, doInBackground, and return the value to a string, the program execute successfully.

However, in my project, I would like to get multiple things from the server. So I would like to use HashMap to help me accomplish this. BUT it raises error. Can anyone tell me why? In addition, when I turn String into HashMap, onPostExecute method's override has an error as well [Method does not override method from its superclass.

Can anybody knows what is going on? My code is shown below.

class retrieveData extends AsyncTask<String,String,String> {
    @Override
    protected void onPreExecute(){
        super.onPreExecute();
        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Please Wait...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

    @Override
    protected HashMap<String, String> doInBackground(String... args){
        // new retrieveData().execute();
        List<NameValuePair> params = new ArrayList<NameValuePair>();

        // getting JSON string from URL
        jsonObject = jsonParser.getJSONFromUrl(REG_URL, params);

        try {
            a = jsonObject.getString("key");
            b = jsonObject.getString("name");
            c = jsonObject.getString("gender");

            // creating new HashMap
            map = new HashMap<String, String>();

            // adding each child node to HashMap key => value
            map.put("key", a);
            map.put("name", b);
            map.put("gender", c);

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return map;
    }

    // SuperClass does not have HashMap imposed...
    @Override
    protected void onPostExecute(HashMap<String, String> map){
        pDialog.dismiss();
        String aReceived = map.get("key");
        String bReceived = map.get("name");
        String cReceived = map.get("gender");
        tv.setText(aReceived + '\n' + bReceived + '\n' + cReceived);
    }
}

Answer 1

It is as simple as,

    class A extends AsyncTask<String, String, HashMap<String, String>>
    {

        @Override
        protected void onPreExecute()
        {
            super.onPreExecute();
            // TODO Auto-generated method stub
        }

        @Override
        protected HashMap<String, String> doInBackground(String... params)
        {
            // TODO Auto-generated method stub
            return null;
        }

        @Override
        protected void onPostExecute(HashMap<String, String> result)
        {
            super.onPostExecute(result);
            // TODO Auto-generated method stub
        }
    }

Answer 2

try this and let me know

class Loaddata extends AsyncTask<HashMap, HashMap, HashMap> {
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    protected HashMap<String, String> doInBackground(HashMap... args) {
        // Building Parameters
        HashMap<String, String> map = new HashMap<String, String>();
        try {

             List<NameValuePair> params = new ArrayList<NameValuePair>();

            // getting JSON string from URL
            jsonObject = jsonParser.getJSONFromUrl(REG_URL, params);

    try {
        a = jsonObject.getString("key");
        b = jsonObject.getString("name");
        c = jsonObject.getString("gender");

        // creating new HashMap
        map = new HashMap<String, String>();

        // adding each child node to HashMap key => value
        map.put("key", a);
        map.put("name", b);
        map.put("gender", c);

    } catch (JSONException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

        } catch (Exception e) {

        }

        return map;
    }

     @Override
protected void onPostExecute(HashMap map){
    pDialog.dismiss();
    String aReceived = map.get("key");
    String bReceived = map.get("name");
    String cReceived = map.get("gender");
    tv.setText(aReceived + '\n' + bReceived + '\n' + cReceived);
}
}