RSS Feed Reader trouble populating listview with the proper

Question

I have the design set up, I need to know how to populate the listview with the URLs RSS feed the user enters in the first activity. Then onClick it opens the 2nd activity which opens a list I need to populate with the user Inputted URL RSS feed. After that I need to click an item from a list an open it in another activity or fragment that displays the RSS news. Below is the working base code for the program, I haven't added the 3rd activity or fragment yet, but am confident I can do that once I figure this part out.

public class MainActivity extends AppCompatActivity {

Button b1;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    b1 = (Button)findViewById(R.id.button);
    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent myIntent = new Intent(MainActivity.this,      ListActivity.class);
            startActivity(myIntent);
        }
    });
  }
}

2nd Activity

public class ListActivity extends MainActivity {
ListView rssList;
private RssData[] listData;

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

    this.generateData();
    rssList = (ListView) this.findViewById(R.id.RssListView);
    RssAdapter listAdapter = new RssAdapter(this,     android.R.layout.simple_list_item_1, listData);
    rssList.setAdapter(listAdapter);
}
//rssNews = (ListView) findViewById(R.id.rssListView);
//rssNews.setAdapter(new RssAdapter(this,rd));

private void generateData() {
    RssData data = null;
    listData = new RssData[10];
    for (int i = 0; i < 10; i++) {
        data = new RssData();
        data.postTitle = "Post " + (i + 1) + " Title: This is the Post Title from RSS Feed";
        listData[i] = data;
    }
}

Here is a class I tried to implement, this goes in onCreate in 2nd Activity

Downloader d = new Downloader();
    d.execute("https://www.google.com");
    try {
        src.setText(d.get());
        }
        catch(Exception e)
        {
            Log.e("ERROR IN THREAD", e.toString());
        }
}

Another class I tried, this would be at end of 2nd activity

class Downloader extends AsyncTask<String, Void, String> {
    public String doInBackground(String... urls) {
        String result = null;
        try
        {
            URL url = new URL(urls[0]);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            InputStream in = conn.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(in));
            String line = null;
            while ((line = reader.readLine()) != null) {
                result = result + line;
            }
            conn.disconnect();
        } catch (Exception e) {
            Log.e("ERROR RETRIEVING", e.toString());
            }
        return result;
    }
}
   //on item selected from listView open new fragment/activity/layout

Adapter

public class RssAdapter extends ArrayAdapter <RssData>
{
private Activity myContext;
private RssData[] datas;

public RssAdapter(Context context, int textViewResourceId,RssData[]objects)
{
    super(context, textViewResourceId, objects);
    myContext = (Activity) context;
    datas = objects;
}

public View getView(int position, View convertView, ViewGroup parent)
{
    View rowView;
    LayoutInflater myInflater;

    if(convertView ==null)
    {
        myInflater = myContext.getLayoutInflater();
        convertView = myInflater.inflate(R.layout.list_item_layout, null);
    }

    rowView = convertView;
    TextView postTitleView = (TextView) rowView.findViewById(R.id.readerViewDescription);
    postTitleView.setText(datas[position].postTitle);

    return rowView;
}
}

Data

public class RssData
{
    public String postThumbUrl;
    public String postTitle;
    public String postDate;
}

XML LAYOUT FILES activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="cj.rssreaderfi.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Enter URL for the desired RSS feed."
    android:id ="@+id/URLTxtBox"/>

<EditText
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id ="@+id/URLEditTxt"
    android:hint="www.Example.com"
    android:layout_below="@+id/URLTxtBox"
    android:layout_alignParentStart="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Retrieve"
    android:id="@+id/button"
    android:layout_below="@+id/URLTxtBox"
    android:layout_toEndOf="@+id/URLTxtBox"
    android:onClick="retrieve"/>
</RelativeLayout>

list_item_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="Medium Text"
    android:id="@+id/readerViewDescription"/>
</LinearLayout>

list_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">

<ListView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/RssListView"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"/>
</LinearLayout>