How to change a variable of an AsyncTask in an activity from another activity by a button click in android studio?

Question

I am using an AsyncTask in my MainActivity in Android Studio, where in doInBackground method, I have an URL, that I want to be changed from a list view item, which is loaded to a listView in HomeActivity.

Is it possible to change the value of the URL to the value of the list item? So I will get a Unique URL every time I click on a list item.

My MainActivity:

package com.example.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;


import android.app.ProgressDialog;
import android.content.Context;
import android.net.ConnectivityManager;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ListView;


import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ArrayList;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

public class MainActivity extends AppCompatActivity {

    ListView lvRss;
    ArrayList<String> titles;
    ArrayList<String> links;
    ArrayList<NewsInformation> news =new ArrayList<>();
    private DatabaseHandler db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lvRss = (ListView) findViewById(R.id.lvRss);

        titles = new ArrayList<String>();
        links = new ArrayList<String>();
        db = new DatabaseHandler(this);


        if(isNetworkAvailable(this)){
            new ProcessInBackground().execute();


        }else {
            try {
                db.open();
                ArrayList<NewsInformation> news = db.getAllNews();
                CustomAdapter adapter = new CustomAdapter(this,news);
                lvRss.setAdapter(adapter);
                db.close();
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }

        }


    }

    public InputStream getInputStream(URL url) {
        try {
            return url.openConnection().getInputStream();
        } catch (IOException e) {
            return null;
        }
    }


    public class ProcessInBackground extends AsyncTask<Integer, Void, Exception> {

        ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);

        Exception exception = null;

        @Override
        protected void onPreExecute() {
            progressDialog.setMessage("Fetching Latest News!");
            progressDialog.show();
        }

        @Override
        protected Exception doInBackground(Integer... integers) {
            try {
                // rss feed site here
                URL url = new URL("https://moxie.foxnews.com/feedburner/sports.xml");

                DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
                DocumentBuilder db = dbf.newDocumentBuilder();

                Document doc = db.parse(getInputStream(url));

                doc.getDocumentElement().normalize();
                NodeList nodeList = doc.getElementsByTagName("item");
                //// fetch every node item in RSS and create news_item list
                for (int i = 0; i < nodeList.getLength(); i++) {
                    NewsInformation news_item = new NewsInformation();
                    Node node = nodeList.item(i);
                    Element parentItem = (Element) node;

                    NodeList links = parentItem.getElementsByTagName("link");
                    Element element_link = (Element) links.item(0);
                    NodeList element_link_childNodes = element_link.getChildNodes();
                    news_item.link = element_link_childNodes.item(0).getNodeValue();


                    NodeList titles = parentItem.getElementsByTagName("title");
                    Element element_title = (Element) titles.item(0);
                    NodeList element_title_childNodes = element_title.getChildNodes();
                    news_item.title = element_title_childNodes.item(0).getNodeValue();


                    NodeList pubDates = parentItem.getElementsByTagName("pubDate");
                    Element element_pubDate = (Element) pubDates.item(0);
                    NodeList element_pubDate_childNodes = element_pubDate.getChildNodes();
                    news_item.pubDate = element_pubDate_childNodes.item(0).getNodeValue();


                    NodeList description = parentItem.getElementsByTagName("description");
                    Element element_description = (Element) description.item(0);
                    if(element_description !=null){
                        NodeList element_description_childNodes = element_description.getChildNodes();
                        news_item.description = element_description_childNodes.item(0).getNodeValue();
                    }else{
                        news_item.description =" ";
                    }

                    NodeList image = parentItem.getElementsByTagName("media:group");
                    Element element_image = (Element) image.item(0);
                    NodeList image_content = element_image.getElementsByTagName("media:content");
                    Element image_content_element = (Element) image_content.item(0);
                    news_item.image = image_content_element.getAttribute("url");
//                    Log.e("IMAGE:",news_item.image);

                    news.add(news_item);



                    //////////////////////////////////////////////////////////////////////////////////////////////



                }




            } catch (MalformedURLException e) {
                exception = e;
                Log.e("IMAGE:","1");

            } catch (IOException e) {
                exception = e;
                Log.e("IMAGE:","2");
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
                Log.e("IMAGE:","3");
            } catch (SAXException e) {
                e.printStackTrace();
                Log.e("IMAGE:","4");
            }
            return null;

        }

        @Override
        protected void onPostExecute(Exception s) {
            super.onPostExecute(s);
            CustomAdapter adapter = new CustomAdapter(getBaseContext(),news);
            lvRss.setAdapter(adapter);

//////////// after fetching data insert to db///////////////////////////////////////////
            try {
                db.open();
                for (int i = 0; i < news.size(); ++i) {
                    db.insertNewsInfo(news.get(i));
                }
                db.close();

            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
/////////////////////////////////////////////////////////////////////////////


            progressDialog.dismiss();

        }
    }

    public boolean isNetworkAvailable(Context context) {
        ConnectivityManager connectivityManager = ((ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE));
        return connectivityManager.getActiveNetworkInfo() != null && connectivityManager.getActiveNetworkInfo().isConnected();
    }
}

In this class I want the value of URL url = new URL("https://moxie.foxnews.com/feedburner/sports.xml"); to be changed.

My HomeActivity

package com.example.myapplication;

import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

import java.util.ArrayList;

public class Home extends AppCompatActivity {

    ListView lst1;
    ArrayList<String> titles = new ArrayList<String>();
    ArrayAdapter arrayAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().getAttributes().windowAnimations = R.style.Fade;
        View decorView = getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
            | View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);
        setContentView(R.layout.activity_home);

        Button button1 = (Button) findViewById(R.id.button1);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(view.getContext(), AddWebsiteActivity.class);
                view.getContext().startActivity(intent);}
        });

        Button button2 = (Button) findViewById(R.id.button2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                this.getRecords();
            }

            private void getRecords() {
                SQLiteDatabase db = openOrCreateDatabase("WebsiteDB", Context.MODE_PRIVATE, null);

                lst1 = findViewById(R.id.lvRssHome);
                final Cursor c = db.rawQuery("select * from records", null);
                int id = c.getColumnIndex("id");
                int name = c.getColumnIndex("name");
                int address = c.getColumnIndex("address");
                titles.clear();


                arrayAdapter = new ArrayAdapter(getApplicationContext(), android.R.layout.simple_expandable_list_item_1, titles);
                lst1.setAdapter(arrayAdapter);

                final ArrayList<WebsitesInformation> stud = new ArrayList<WebsitesInformation>();


                if (c.moveToFirst()) {
                    do {
                        WebsitesInformation stu = new WebsitesInformation();
                        stu.id = c.getInt(id);
                        stu.name = c.getString(name);
                        stu.address = c.getString(address);
                        stud.add(stu);

                        titles.add(c.getString(id) + " \t" + c.getString(name));

                    } while (c.moveToNext());
                    arrayAdapter.notifyDataSetChanged();
                    lst1.invalidateViews();


                }

                lst1.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        Intent i = new Intent(getApplicationContext(), MainActivity.class);

                        startActivity(i);

                    }
                });
            }


        });

    }

}

Here I want the address value in the listView to be transferred to the URL value in MainActivity

Answer 1

First of all why AsyncTask? Its already deprecated and comes with many issues. https://developer.android.com/reference/android/os/AsyncTask

You can simply use coroutines. its super easy and less complicated. or you can even use rxjava.

Secondly, your AsyncTask is designed in a wrong way. Do the following.

1. Define your async task to take strings

public class ProcessInBackground extends AsyncTask<String, Void, Exception> {

2. then your doInBackground will look something like this:

        @Override
        protected Exception doInBackground(String... strings) {
                URL url = new URL(strings[0]);
        }

3. execute the asyncTask by calling it this way.

new ProcessInBackground().execute("pass_your_url_from_list");

Just dont use AsyncTask.