How to create an Adapter for a ListView from an AsyncTask?

Question

Java

Loading data from the server.

public class ServerTask extends AsyncTask<Void,Void,ArrayList<Map<String, String>>> {

        protected void onPreExecute(){}

        @Override
        protected ArrayList<Map<String, String>> doInBackground(Void... voids) {
            return ServerRequest.getRecipesList();
        }

        @Override
        protected void onPostExecute(ArrayList<Map<String, String>> list) {
            super.onPostExecute(list);
        }
    }

I also have my adapter.

RecipeListAdapter(Context context, ArrayList<Map<String, String>> list) {
    //...code...
}

The application was created according to a template with a pull-down menu (NavigationDrawerFragment).
In "R.layout.fragment_main" there is a ListView for which you need to create and pass an Adapter, I can't figure out how to do it. Here is the whole Activity code, just in case.
Help please =(

import android.app.Activity;

import android.app.ActionBar;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import android.widget.ListView;

import com.cooknote.blackice.cooknote.adapters.RecipeListAdapter;

import org.json.JSONObject;

import java.util.ArrayList;
import java.util.Map;

public class Main extends Activity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    public class ServerTask extends AsyncTask<Void,Void,ArrayList<Map<String, String>>> {

        int type = 0;
        ListView lv;

        ServerTask(int type, ListView lv) {
            this.type = type;
            this.lv = lv;
        }

        protected void onPreExecute(){}

        @Override
        protected ArrayList<Map<String, String>> doInBackground(Void... voids) {
            return ServerRequest.getRecipesList();
        }

        @Override
        protected void onPostExecute(ArrayList<Map<String, String>> list) {
            super.onPostExecute(list);
        }
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {
        // update the main content by replacing fragments
        FragmentManager fragmentManager = getFragmentManager();
        fragmentManager.beginTransaction().replace(R.id.container, PlaceholderFragment.newInstance(position + 1)).commit();
    }

    public void onSectionAttached(int number) {
        switch (number) {
            case 1:
                mTitle = getString(R.string.title_section1);
                break;
            case 2:
                mTitle = getString(R.string.title_section2);
                break;
            case 3:
                mTitle = getString(R.string.title_section3);
                break;
            case 4:
                mTitle = getString(R.string.title_section4);
                break;
            case 5:
                mTitle = getString(R.string.title_section5);
                break;
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.main, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            ListView mListView = (ListView) rootView.findViewById(R.id.listView);
            //RecipeListAdapter a = new RecipeListAdapter(getActivity(), list);
            //mListView.setAdapter(a);
            return rootView;
        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            ((Main) activity).onSectionAttached(getArguments().getInt(ARG_SECTION_NUMBER));
        }
    }
}

Answer 1

The fragment calls AsyncTask and sets the adapter in onPostExecute (runs on the UI thread), like so:

public static class PlaceholderFragment extends Fragment {

...

@Override
    public void onResume() {
        super.onResume();
        new ServerTask(yourType, yourListView).execute();
    }

...

}

public class ServerTask extends AsyncTask<Void,Void,ArrayList<Map<String, String>>> {
        
        int type = 0;
        ListView lv;

        ServerTask(int type, ListView lv) {
            this.type = type;
            this.lv = lv;
        }

        ...

        @Override
        protected void onPostExecute(ArrayList<Map<String, String>> list) {
            super.onPostExecute(list);
            lv.setAdapter(new RecipeListAdapter(getActivity(), list));
        }
    }

Answer 2

I would do it via ContentProvider. In the task, it is written to the database, your adapter is inherited from CursorAdapter. Check out this tutorial www.vogella.com/tutorials/AndroidSQLite/article.html.