Blog Reader app is not working and showing anything in the device .

package com.aspricot.blogreader;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.HashMap;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.app.AlertDialog;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.Html;
import android.util.Log;
import android.view.View;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;

public class MainListActivity extends ListActivity {


public static final int Number_Of_Posts = 20;
public static final String TAG = MainListActivity.class.getSimpleName();

protected JSONObject mBlogData;
protected ProgressBar mProgressBar;
private final String KEY_TITLE = "title";
private final String KEY_AUTHOR ="author";
@Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_list);

    mProgressBar = (ProgressBar) findViewById(R.id.progressBar1);
if(isNetworkAvailabel()) {
       mProgressBar.setVisibility(View.VISIBLE);

       GetBlogPostsTask getBlogPostsTask = new GetBlogPostsTask();
        getBlogPostsTask.execute();
}



Toast.makeText(this, "network is unavailable", Toast.LENGTH_LONG).show();
//Toast.makeText(this , message , Toast.LENGTH_LONG ).show();
}



@Override
protected void onListItemClick(ListView l , View v ,int position , long id) {
    super.onListItemClick(l, v, position, id);
    try {
        JSONArray jsonPosts = mBlogData.getJSONArray("posts");
        JSONObject jsonPost = jsonPosts.getJSONObject(position);
        String blogUrl = jsonPost.getString("url");
        Intent intent = new Intent(this , BlogWebViewActivity.class);
        intent.setData(Uri.parse(blogUrl));
        startActivity(intent);
    } catch (JSONException e) {
        logException(e);
    }
}



private void logException(Exception e) {
    Log.e(TAG , "Exception Caught!" , e);
}

private boolean isNetworkAvailabel() {
    ConnectivityManager manager = (ConnectivityManager) 
            getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = manager.getActiveNetworkInfo();

 boolean isAvailable = false; 
 if (networkInfo != null && networkInfo.isConnected()){
     isAvailable = true;
 }
 return isAvailable;
}


public void handleBlogResponse() {
    mProgressBar.setVisibility(View.INVISIBLE);
    if(mBlogData ==  null){
        updateDisplayForError();


    }
    else {
        try {
            JSONArray jsonPosts = mBlogData.getJSONArray("posts");
        ArrayList<HashMap<String , String>> blogPosts =
                new ArrayList<HashMap<String , String>>();
         for(int i = 0; i < jsonPosts.length(); i ++)   {
             JSONObject post = jsonPosts.getJSONObject(i);
             String title = post.getString(KEY_TITLE);
             title = Html.fromHtml(title).toString();
             String author = post.getString(KEY_AUTHOR);
             author = Html.fromHtml(title).toString();

             HashMap<String , String> blogPost = new HashMap<String,String>();
             blogPost.put(KEY_TITLE ,title);
             blogPost.put(KEY_AUTHOR, author);

             blogPosts.add(blogPost);
         }
       String[] keys = { KEY_TITLE , KEY_AUTHOR };
       int[] ids = { android.R.id.text1 , android.R.id.text2 };
       SimpleAdapter adapter = new SimpleAdapter(this, blogPosts, 
               android.R.layout.simple_list_item_2, keys, ids);
         setListAdapter(adapter);
        } 
        catch (JSONException e) {
        Log.e(TAG , "Exception Caught:" , e);
        }
    }
}



private void updateDisplayForError() {
    AlertDialog.Builder builder  = new AlertDialog.Builder(this);
    builder.setTitle(getString(R.string.error_title));
    builder.setMessage(getString(R.string.error_message));
    builder.setPositiveButton(android.R.string.ok , null);
    AlertDialog dialog = builder.create();
    dialog.show();

    TextView emptyTextView = (TextView) getListView().getEmptyView();
    emptyTextView.setText(getString(R.string.no_items));
}
private class GetBlogPostsTask extends AsyncTask<Object, Void, JSONObject> {

    @Override
    protected JSONObject doInBackground(Object... arg0) {

        int responseCode = -1;
        JSONObject jsonResponse = null;
        try {
        URL blogFeedUrl = new URL("http://blog.teamtreehouse.com/api/get_recent_summary/?count=20" + Number_Of_Posts);
        HttpURLConnection connection = (HttpURLConnection) blogFeedUrl.openConnection();
        connection.connect();

        responseCode = connection.getResponseCode();
        if(responseCode == HttpURLConnection.HTTP_OK){
            InputStream inputStream = connection.getInputStream();
            Reader reader = new InputStreamReader(inputStream);
            int contentLength = connection.getContentLength();
            char[] charArray = new char[contentLength];
            reader.read(charArray);
            String responseData = new String(charArray);

             jsonResponse = new JSONObject(responseData);

        }
            else{   Log.i(TAG , "Unsuccessful http Code:" + responseCode);
        }
        }
        catch(MalformedURLException e) {
            logException(e);
        }
    catch(IOException e) {
        logException(e);
    }
  catch(Exception e) {
      logException(e);
  }
        return jsonResponse;


    }
}
protected void onPostExecute(JSONObject result){
    mBlogData = result;

}




}