// required according facebook android sdk documentation
 public void onActivityResult(int requestCode, int resultCode, Intent data) {
   super.onActivityResult(requestCode, resultCode, data);
   facebook.authorizeCallback(requestCode, resultCode, data);
 }
  @Override
  public void onCreate(Bundle savedInstanceState) {
    // locks the screen in portrait mode
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    super.onCreate(savedInstanceState);
    setContentView(R.layout.downloader);
    mtext = (TextView) findViewById(R.id.mtext);
    progress_text = (TextView) findViewById(R.id.progress_text);
    progress_download = (ProgressBar) findViewById(R.id.progress_download);
    // resume capability

    paused = false;
    resume_pause = (Button) findViewById(R.id.resume);

    // Create and launch the download thread
    downloadThread = new DownloadThread(this);
    downloadThread.start();

    // Create the Handler. It will implicitly bind to the Looper
    // that is internally created for this thread (since it is the UI thread)
    handler = new Handler();

    resume_pause.setOnClickListener(
        new View.OnClickListener() {
          public void onClick(View v) {
            if (!paused) {
              paused = true;
              resume_pause.setText("Resume");
              // writeProgress(completed_downloads,total_files_to_download);
              downloadThread.requestStop();
              downloadThread = null;

            } else {
              resume_pause.setText("Pause");
              paused = false;

              initial_value = readProgress()[0];
              final_value = links.size();

              for (int i = initial_value; i < links.size(); i++) {
                downloadThread = new DownloadThread(download_photos.this);
                downloadThread.start();
                downloadThread.enqueueDownload(
                    new DownloadTask(
                        links.get(i), path, i + 1, links.size(), download_photos.this));
              }
            }
          }
        });

    // load preferences for this activity
    mPrefs = getSharedPreferences("COMMON", MODE_PRIVATE);

    // This declaration is solely meant for reading the checkbox preference for downloading high res
    // pics.
    SharedPreferences dl_prefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

    // The global variable is set after reading the  checkbox preference.
    dl_high_res_pics = dl_prefs.getBoolean("download_high_res", false);

    // load fb access token and its expiry values
    String access_token = mPrefs.getString("access_token", null);
    long expires = mPrefs.getLong("access_expires", 0);

    if (access_token != null) {
      facebook.setAccessToken(access_token);
    }
    if (expires != 0) {
      facebook.setAccessExpires(expires);
    }

    // get friend_name and album_name from the intent which started this activity
    Intent starting_intent = getIntent();
    album_id = starting_intent.getStringExtra("id");
    album_name = starting_intent.getStringExtra("name");
    friend_name = starting_intent.getStringExtra("friend_name");

    // real album and friend name may contain characters not suitable for file names.
    // regex pattern includes most of the invalid characters in file names
    legal_album_name = album_name.replaceAll("[.\\\\/:*?\"<>|]?[\\\\/:*?\"<>|]*", "");
    legal_friend_name = friend_name.replaceAll("[.\\\\/:*?\"<>|]?[\\\\/:*?\"<>|]*", "");

    // initialise the directory structure for download
    path =
        new File(
            Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
                + "/"
                + getText(R.string.app_name)
                + "/"
                + legal_friend_name
                + "/"
                + legal_album_name);
    if (dl_high_res_pics)
      path = new File(path.toString() + "/" + getText(R.string.folder_name_high_res));

    resume_file = new File(path, "resume.txt");
    // implements actions to done after receiving json object
    class meRequestListener extends BaseRequestListener {
      @Override
      public void onComplete(String response, Object state) {
        try {
          Log.i(TAG, response);
          json = Util.parseJson(response);

          // photos are in the form of a json array
          child = json.getJSONArray("data");

          int total = child.length();

          // contains links to photos
          links = new ArrayList<String>(total);

          // adds link to each photo to our list after replacing the "https" from url
          // DownloadManager does not support https in gingerbread
          for (int i = 0; i < total; i++) {
            photo_json = child.getJSONObject(i);

            if (dl_high_res_pics) {
              JSONArray image_set = photo_json.getJSONArray("images");

              // highest resolution picture has the index zero in the images jsonarray
              JSONObject highest_res_pic = image_set.getJSONObject(0);
              String http_replaced =
                  highest_res_pic.getString("source").replaceFirst("https", "http");
              links.add(i, http_replaced);
            } else {
              // source property of the json object points to the photo's link
              String http_replaced = photo_json.getString("source").replaceFirst("https", "http");
              links.add(i, http_replaced);
            }
          }

          download_photos.this.runOnUiThread(
              new Runnable() {
                public void run() {
                  //	mytask = new DownloadImageTask();
                  //	mytask.execute(links);
                  // start downloading using asynctask
                  // new DownloadImageTask().execute(links);
                  // downloadThread.setPath(path);
                  // downloadThread.setWholeTasks(links.size());
                  if (resume_file.exists()) {

                    initial_value = readProgress()[0];
                    final_value = links.size();
                    // case if the task is already completed
                    if (initial_value == final_value) {
                      completed = true;
                      resume_pause.setVisibility(View.GONE);

                      progress_download.setMax(final_value);
                      progress_download.setProgress(0); // bug in progress bar
                      progress_download.setProgress(initial_value);

                      progress_text.setText("Completed.");
                      mtext.setText(
                          getText(R.string.download_textview_message_1)
                              + " "
                              + path.toString()
                              + ". ");

                    }

                    // case if some of the photos are already downloaded
                    else {
                      progress_download.setMax(links.size());
                      // progress_download.setProgress(0);	//bug in progress bar
                      progress_download.setProgress(initial_value);

                      // N.B if i= initial_value -1, then one image will be downloaded again. so to
                      // save cost we start with i = initial_value
                      for (int i = initial_value; i < links.size(); i++) {
                        mtext.setText(
                            getText(R.string.download_textview_message_1)
                                + " "
                                + path.toString()
                                + ". ");
                        // downloadThread.setRunningTask(i + 1);
                        downloadThread.enqueueDownload(
                            new DownloadTask(
                                links.get(i), path, i + 1, final_value, download_photos.this));
                      }
                    }
                  }

                  // case if the task is entirely new task
                  else {
                    for (int i = 0; i < links.size(); i++) {
                      mtext.setText(
                          getText(R.string.download_textview_message_1)
                              + " "
                              + path.toString()
                              + ". ");
                      // downloadThread.setRunningTask(i + 1);
                      downloadThread.enqueueDownload(
                          new DownloadTask(
                              links.get(i), path, i + 1, links.size(), download_photos.this));
                    }
                  }
                }
              });
        } catch (JSONException ex) {
          Log.e(TAG, "JSONEXception : " + ex.getMessage());
        }
      }
    }

    // makes asynchronous request to facebook graph api
    // the actions to be performed after receiving json response is implemented above

    Bundle parameters = new Bundle();

    // facebook returns only 25 photos when limit is not specified.
    parameters.putString("limit", max_photos_in_album);
    if (!completed) mAsyncRunner.request(album_id + "/photos", parameters, new meRequestListener());

    if (!facebook.isSessionValid()) {
      facebook.authorize(
          this,
          permissions,
          new DialogListener() {

            // save fb access token and its expiry values to prefernces of this activity
            @Override
            public void onComplete(Bundle values) {
              SharedPreferences.Editor editor = mPrefs.edit();
              editor.putString("access_token", facebook.getAccessToken());
              editor.putLong("access_expires", facebook.getAccessExpires());
              editor.commit();
            }

            @Override
            public void onFacebookError(FacebookError error) {
              Log.e(TAG, "Facebook Error : " + error.getMessage());
            }

            @Override
            public void onError(DialogError e) {
              Log.e(TAG, e.getMessage());
            }

            @Override
            public void onCancel() {
              // do nothing LOL :-)
            }
          });
    }
  }