isNetworkAvailable not returning to true,

public class MainListActivity extends ListActivity{

    protected String[] BlogPostTitle;
    public static final int NUMBER_OF_POST = 20;
    public static final String TAG = MainListActivity.class.getSimpleName();


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

        if(isNetworkAvailable()){
            GetBlogPostTask getBlogPostTask = new GetBlogPostTask();
            getBlogPostTask.execute();

        }
        else{
            Toast.makeText(this, "Network is unavailable", Toast.LENGTH_LONG).show();

        }
        //Toast.makeText(this, getString(R.string.no_item),Toast.LENGTH_LONG).show();
    }

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

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_list, menu);
        return true;
    }

    @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);
    }

    public class GetBlogPostTask extends AsyncTask<Object, Void, String> {

        @Override
        protected String doInBackground(Object... arg0) {
            int responseCode = -1;

            try{
                URL blogFeedURL = new URL("http://blog.teamtreehouse.com/api/get_recent_summary/?count=" + NUMBER_OF_POST);
                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);
                    Log.v(TAG, responseData);
                }
                else{
                    Log.i(TAG, "Unsuccessfull HTTP response code: " + responseCode);
                }
            }
            catch(MalformedURLException e){
                Log.e(TAG,"Error ditemukan: ", e);
            }
            catch(IOException e){
                Log.e(TAG,"Error ditemukan: ",e);
            }
            catch(Exception e){
                Log.e(TAG,"Error ditemukan: ",e);
            }

            return "Get code: " + responseCode;

        }
    }

}