Google Play Developer Console has a limitation that doesn’t allow users to upload the APK file of more than 50 MB size. However, some android apps need more space for high-fidelity graphics, media files, or other large assets. Previously, if your app exceeded 50MB, you had to host and download the additional resources yourself.

How to make expansion file?

Make a zip folder of your assets like audio files, video files, images or anything you want to use in your app. Rename your zip file into below format.

[main/patch].<expansion-version>.<package-name>.obb

For example, your APK version is 1000 and your package name is com.example.app. If you upload a main expansion file, the file name should be main.1000.com.example.app.obb

Now your zip file is ready to upload.

Storage location

When Google Play downloads your expansion files to a device, it saves them to the system’s shared storage location. The specific location for your expansion files is: <shared-storage>/Android/obb/<package-name>/

 When you download an app with expansion file from play store, your expansion file will be downloaded to ../Android/obb/main.1000.com.example.app.obb location.

Declaring user permissions Required

In order to download the expansion files, the Downloader Library requires several permissions that you must declare in your application’s manifest file. They are:

 

<manifest ...>
   <!-- Required to access Google Play Licensing -->
   <uses-permission android:name="com.android.vending.CHECK_LICENSE" />
    <!-- Required to download files from Google Play -->
   <uses-permission android:name="android.permission.INTERNET" />
    <!-- Required to keep CPU alive while downloading files
       (NOT to keep screen awake) -->
   <uses-permission android:name="android.permission.WAKE_LOCK" />
    <!-- Required to poll the state of the network connection
       and respond to changes -->
   <uses-permission
       android:name="android.permission.ACCESS_NETWORK_STATE" />
    <!-- Required to check whether Wi-Fi is enabled -->
   <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
    <!-- Required to read and write the expansion files on shared storage -->
   <uses-permission
       android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
   ...
</manifest>

 

Note: By default, the Downloader Library requires API level 4, but the APK Expansion Zip Library requires API level 5.

How to import zip file library?

Zip_file library is used to extract your expansion file in your sdcard. Import it from below SDK path.

Eclipseandroid-sdkextrasgoogleplay_apk_expansionzip_file

How to use your expansion file from MainActivity.java

Below function is used to extract your expansion file using ZipHelper.java and create directory of extracted data from your expansion file.

public void ZipHelperNew() {

ZipResourceFile expansionFile = null;

try {

expansionFile = APKExpansionSupport.getAPKExpansionZipFile(

getApplicationContext(), versioncode, 0);

ZipEntryRO[] zip = expansionFile.getAllEntries();

Log.e("", "zip[0].isUncompressed() : " +  zip[0].isUncompressed());

Log.e("","mFile.getAbsolutePath() : "+ zip[0].mFile.getAbsolutePath());

Log.e("", "mFileName : " + zip[0].mFileName);

Log.e("", "mZipFileName : " + zip[0].mZipFileName);

Log.e("", "mCompressedLength : " + zip[0].mCompressedLength);

String hallostring = zip[0].mFileName;

String asubstring = hallostring.substring(0, 40);

File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/dirName");

ZipHelper.unzip(zip[0].mZipFileName, file);

if (file.exists()) {

Log.e("", "unzipped Success: " + file.getAbsolutePath());
}

} catch (IOException e) {
e.printStackTrace();
}
}

Extract your expansion file using ZipHelper.java

This ZipHelper.java is used to extract the expansion file with above code.

public class ZipHelper {

static boolean zipError = false;

public static boolean isZipError() {

return zipError;
}

public static void setZipError(boolean zipError) {

   ZipHelper.zipError = zipError;
}

public static void unzip(String archive, File outputDir) {

   try {

       Log.d("control", "ZipHelper.unzip() - File: " + archive);

       ZipFile zipfile = new ZipFile(archive);

       for (Enumeration<? extends ZipEntry> e = zipfile.entries(); e

               .hasMoreElements();) {

           ZipEntry entry = (ZipEntry) e.nextElement();

           unzipEntry(zipfile, entry, outputDir);
         }

   } catch (Exception e) {

       Log.d("control", "ZipHelper.unzip() - Error extracting file "

               + archive + ": " + e);

       setZipError(true);
   }

}

private static void unzipEntry(ZipFile zipfile, ZipEntry entry,

File outputDir) throws IOException {

   if (entry.isDirectory()) {

       createDirectory(new File(outputDir, entry.getName()));

       return;
   }

File outputFile = new File(outputDir, entry.getName());

   if (!outputFile.getParentFile().exists()) {

       createDirectory(outputFile.getParentFile());

   }

Log.d("control", "ZipHelper.unzipEntry() - Extracting: " + entry);

   BufferedInputStream inputStream = new BufferedInputStream(

           zipfile.getInputStream(entry));

   BufferedOutputStream outputStream = new BufferedOutputStream(

           new FileOutputStream(outputFile));

try {

       IOUtils.copy(inputStream, outputStream);

} catch (Exception e) {

       Log.d("control", "ZipHelper.unzipEntry() - Error: " + e);

       setZipError(true);

} finally {

       outputStream.close();

       inputStream.close();

}
}

private static void createDirectory(File dir) {

   Log.d("control",

           "ZipHelper.createDir() - Creating directory: " + dir.getName());

   if (!dir.exists()) {

       if (!dir.mkdirs())

           throw new RuntimeException("Can't create directory " + dir);

   } else

       Log.d("control",

               "ZipHelper.createDir() - Exists directory: "

                       + dir.getName());
   }

}

Your expansion file has now been extracted to your SD card.

How to get count of images, mp4 and mp3 stored in SD card directory.

Try below code to get a total number of count from sdcard directory.

 String filePath = "/mnt/sdcard/dirName/";

File file = new File(filePath);

if (file.exists()) {

File fileCount = new File("/mnt/sdcard/dirName/);

File[] list = fileCount.listFiles();

for (File f : list) {

String name = f.getName();

if (name.endsWith(".jpg") || name.endsWith(".mp3") || name.endsWith(".mp4"))

Sdcardcount++;

}
}

Above code will get you a list of files stored in particular directory.

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Author : Multidots
Multidots is full service enterprise software development company with services revolving around consulting, enterprise-grade custom application development, custom mobile and cloud applications to automated and manual testing. We are proud to have served mid-sized to large enterprises including Fortune 500 Companies in our clientele.

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