compression

The Phimpme Android application comes in with all the functionalities ranging from viewing images to taking photos, editing pictures  and sharing them with the world from within a single application without having to switch to or install other social media apps on your mobile phone. Apart from these basic functionalities, the Phimpme Android app also comes with additional features to enhance user experience like the ability to compress the whole album with a large number of photos so that it becomes easier to share them. In this post, I will be explaining how we achieved this functionality to compress the Albums.

Step 1

The first thing we need to do before compressing an album is to get all the paths of the images in that album and store it in an ArrayList<String> so that it can be used later for the compression process. This can be done using the code snippet provided below, it stores all the paths of the file in a particular folder whose name ends with .jpg

path = new ArrayList<>();
File folder = new File(getAlbums().getSelectedAlbum(0).getPath() + "/");
File[] fpath = folder.listFiles();
for(int i = 0; i < fpath.length; i++){
   if(fpath[i].getPath().endsWith(".jpg") ){
       path.add(fpath[i].getPath());
   }
}

Step 2

Since the compression is a heavy task, we can make use of an AsyncTask to run the task on the background thread so that the user experience is not at all hampered. In the onPreExecute method of the AsyncTask, we need to display the Notification that the compression of the particular album has started, for this we have made use of the Notification handler class that we have created in the Phimpme Android application to ease the process of displaying the notification and to avoid repetition of codes. The onPreExecute method of the AsyncTask is given below.

@Override
protected void onPreExecute() {
   super.onPreExecute();
   NotificationHandler.make(R.string.folder, R.string.zip_fol, R.drawable.ic_archive_black_24dp );
}

Step 3

On the doInBackground method of the AsyncTask, we run the process to compress the files one by one. For this we will make use of the ZipEntry class which is used to represent a zip file entry in Android/Java. First we will create a File with the .zip extension.  After this, we will make use of an object of the class ZipOutputStream as depicted in the code snippet provided below.

BufferedInputStream origin = null; 
FileOutputStream dest = new FileOutputStream(_zipFile); 
ZipOutputStream out = new ZipOutputStream(new BufferedOutputStream(dest)); 
byte data[] = new byte[BUFFER];

After initializing the ZipOutPutStream object, we will put the zip entries in it by using the putNextEntry function of the class. To create a Zip entry of a file, we need to make use of for loop to generate the object of type ZipEntry and after that by using the putNextEntry function of the class, we will put the entries one by one as depicted in the code snippet given below.

for (int i = 0; i < path.size(); i++) {
FileInputStream fi = new FileInputStream(path.get(i));
origin = new BufferedInputStream(fi, BUFFER);
ZipEntry entry = new ZipEntry(path.get(i).substring(path.get(i).lastIndexOf("/") + 1));
out.putNextEntry(entry);

While preparing the Zip file, we will update the progress of the compression operation by making use of the Notification handler class.

This is how we have implemented the feature to compress the Albums in the Phimpme Android Application. To get the full source code for the same, please check the Phimpme Android GitHub repository listed on the resources below.

Resources

1. StackOverflow – Compressing Files in Android – https://stackoverflow.com/questions/25562262/how-to-compress-files-into-zip-folder-in-android
2. Blog – Compressing Files in Android programmatically – http://stacktips.com/tutorials/android/how-to-programmatically-zip-and-unzip-file-in-android
3. GitHub – Phimpme Android Repository – https://github.com/fossasia/phimpme-android/