The Phimpme Android application features a fully fledged gallery interface with an option to switch to all photos mode, albums mode and to sort photos according to various sort actions. Sorting photos via various options helps the user to get to the desired photo immediately without having to scroll down till the end in case it is the last photo in the list generated automatically by scanning the phone for images using the Android’s mediaStore class. In this tutorial, I will be discussing how we achieved the sorting option in the Phimpme application with the help of some code snippets.

To sort the all photos list, first of all we need a list of all the photos by scanning the phone using the media scanner class via the code snippet provided below:

uri = android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
      String[] projection = {MediaStore.MediaColumns.DATA};
      cursor = activity.getContentResolver().query(uri, projection, null, null, null);

In the above code we are using a cursor to point to each photos and then we are extracting the path of the images and storing it in a list using a while loop. After we generate the list of path of all the images, we have to convert the into a list of media using the file path using the code below:

for (String path : listOfAllImages) {
          list.add(new Media(new File(path)));
      }
      return list;
  }

After generating the list of all images we can sort the photos using the Android’s collection class. In Phimpme Android we provide the option to sort photos in different categories namely:

1. Name Sort action
2. Date Sort action
3. Size Sort action
4. Numeric Sort action

As sorting is somewhat heavy task so doing this in the main thread will result in freezing UI of the application so we have to put this into an AsyncTask with a progress dialog to sort the photos. After putting the above four options in the menu options. We can define an Asynctask to load the images and in the onPreExecute method of the AsyncTask, we are displaying the progress dialog to the user to depict that the sorting process is going on as depicted in the code snippet below

AlertDialog.Builder progressDialog = new AlertDialog.Builder(LFMainActivity.this, getDialogStyle());
dialog = AlertDialogsHelper.getProgressDialog(LFMainActivity.this, progressDialog,
      getString(R.string.loading_numeric), all_photos ? getString(R.string.loading_numeric_all) : getAlbum().getName());
dialog.show();

In the doInBackgroundMethod of the AsyncTask, we are sorting the list of all photos using the Android’s collection class and using the static sort method defined in that class which takes the list of all the media files as a parameter and the MediaComparator which takes the sorting mode as the first parameter and the sorting order as the second. The sorting order decides whether to arrange the list in ascending or in descending order.

getAlbum().setDefaultSortingMode(getApplicationContext(), NUMERIC);
Collections.sort(listAll, MediaComparators.getComparator(getAlbum().settings.getSortingMode(), getAlbum().settings.getSortingOrder()));

After sorting, we have to update the data set to reflect the changes of the list in the UI. This we are doing in the onPostExecute method of the AsyncTask after dismissing the progress Dialog to avoid the window leaks in the application. You can read more about the window leaks in Android due to progressdialog here.

dialog.dismiss();
mediaAdapter.swapDataSet(listAll);

To get the full source code, you can refer the Phimpme Android repository listed in the resources below.

Resources

1. Android developer guide to mediastore class: https://developer.android.com/reference/android/provider/MediaStore.html
2. GitHub LeafPic repository: https://github.com/HoraApps/LeafPic
3. Stackoverflow – Preventing window leaks in Android: https://stackoverflow.com/questions/6614692/progressdialog-how-to-prevent-leaked-window
4. Blog – Sorting lists in Android: http://www.worldbestlearningcenter.com/tips/Android-sort-ListView.htm