APK Expansion Files | Android Developers

Important: From August 2021, new apps are required to publish with the
Android App Bundle on
Google Play. New apps larger than 150 MB are now supported by either
Play Feature Delivery or
Play Asset Delivery.

Google Play requires that the compressed APK that users download be no more than 100MB. For most apps, this is plenty of space for all the app’s code and assets. However, some apps need more space for high-fidelity graphics, truyền thông files, or other large assets. Previously, if your app’s compressed download size exceeded 100MB, you had to host and download the additional resources yourself when the user opens the app. Hosting and serving the extra files can be costly, and the user experience is often less than ideal. To make this process easier for you and more pleasant for users, Google Play allows you to attach two large expansion files that supplement your APK .
Google Play hosts the expansion files for your app and serves them to the device at no cost to you. The expansion files are saved to the device’s shared storage location ( the SD card or USB-mountable partition ; also known as the ” external ” storage ) where your app can access them. On most devices, Google Play downloads the expansion file ( s ) at the same time it downloads the APK, so your app has everything it needs when the user opens it for the first time. In some cases, however, your app must download the files from Google Play when your app starts .
If you’d like to avoid using expansion files and your app’s compressed download size is larger than 100 MB, you should instead upload your app using Android App Bundles which allows for up to a 150 MB compressed download size. Additionally, because using app bundles defers APK generation and signing to Google Play, users download optimized APKs with only the code and resources they need to run your app. You don’t have to build, sign, and manage multiple APKs or expansion files, and users get smaller, more optimized downloads .

Overview

Each time you upload an APK using the Google Play Console, you have the option to
add one or two expansion files to the APK. Each file can be up to 2GB and it can be any format you
choose, but we recommend you use a compressed file to conserve bandwidth during the download.
Conceptually, each expansion file plays a different role:

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The main expansion file is the
primary expansion file for additional resources required by your app.

The patch expansion file is optional and intended for small updates to the
main expansion file.

While you can use the two expansion files any way you wish, we recommend that the main expansion file deliver the primary assets and should rarely if ever updated ; the patch expansion file should be smaller and serve as a “ patch carrier, ” getting updated with each major release or as necessary .

However, even if your app update requires only a new patch expansion file, you still must
upload a new APK with an updated versionCode in the manifest. (The
Play Console does not allow you to upload an expansion file to an existing APK.)

Note: The patch expansion file is semantically the same as the
main expansion file—you can use each file any way you want.

File name format

Each expansion file you upload can be any format you choose ( ZIP, PDF, MP4, etc. ). You can also use the JOBB tool to encapsulate and encrypt a set of resource files and subsequent patches for that set. Regardless of the file type, Google Play considers them opaque binary blobs and renames the files using the following scheme :
[main|patch]...obb
There are three components to this scheme :

main or patch

Specifies whether the file is the main or patch expansion file. There can be
only one main file and one patch file for each APK.

This is an integer that matches the version code of the APK with which the expansion is
first associated (it matches the app’s android:versionCode
value).
” First ” is emphasized because although the Play Console allows you to re-use an uploaded expansion file with a new APK, the expansion file’s name does not change — it retains the version applied to it when you first uploaded the file .

Your app’s Java-style package name.

For example, suppose your APK version is 314159 and your package name is com.example.app. If you upload a main expansion file, the file is renamed to :
main.314159.com.example.app.obb
Storage location

When Google Play downloads your expansion files to a device, it saves them to the system’s shared storage location. To ensure proper behavior, you must not delete, move, or rename the expansion files. In the sự kiện that your app must perform the download from Google Play itself, you must save the files to the exact same location .

The getObbDir() method returns the specific location
for your expansion files in the following form:
/Android/obb//
is the path to the shared storage space, available from
getExternalStorageDirectory().

is your app’s Java-style package name, available
from getPackageName().

For each app, there are never more than two expansion files in this directory.
One is the main expansion file and the other is the patch expansion file (if necessary). Previous
versions are overwritten when you update your app with new expansion files. Since Android
4.4 (API level 19), apps can read OBB expansion files without external storage
permission. However, some implementations of Android 6.0 (API level 23) and later still require
permission, so you will need to declare the
READ_EXTERNAL_STORAGE permission in the app manifest and ask for permission at
runtime as follows:
For Android version 6 and later, external storage permission needs to be requested at runtime. However, some implementations of Android do not require permission to read OBB files. The following code snippet shows how to check for read access before asking for external storage permission :

Kotlin
val obb = File(obb_filename)
var open_failed = false

try {
    BufferedReader(FileReader(obb)).also { br ->
        ReadObbFile(br)
    }
} catch (e: IOException) {
    open_failed = true
}

if (open_failed) {
    // request READ_EXTERNAL_STORAGE permission before reading OBB file
    ReadObbFileWithPermission()
}
Java
File obb = new File(obb_filename);
 boolean open_failed = false;

 try {
     BufferedReader br = new BufferedReader(new FileReader(obb));
     open_failed = false;
     ReadObbFile(br);
 } catch (IOException e) {
     open_failed = true;
 }

 if (open_failed) {
     // request READ_EXTERNAL_STORAGE permission before reading OBB file
     ReadObbFileWithPermission();
 }
If you must unpack the contents of your expansion files, do not delete the
OBB expansion files afterwards and do not save the unpacked data
in the same directory. You should save your unpacked files in the directory
specified by getExternalFilesDir(). However,
if possible, it’s best if you use an expansion file format that allows you to read directly from
the file instead of requiring you to unpack the data. For example, we’ve provided a library
project called the APK Expansion Zip Library that reads your data directly
from the ZIP file.

Caution: Unlike APK files, any files saved
on the shared storage can be read by the user and other apps.

Tip: If you’re packaging media files into a ZIP, you can use media
playback calls on the files with offset and length controls (such as MediaPlayer.setDataSource() and
SoundPool.load()) without the
need to unpack your ZIP. In order for this to work, you must not perform additional compression on
the media files when creating the ZIP packages. For example, when using the zip tool,
you should use the -n option to specify the file suffixes that should not be
compressed:
zip -n .mp4;.ogg main_expansion media_files

Download process

Most of the time, Google Play downloads and saves your expansion files at the same time it downloads the APK to the device. However, in some cases Google Play cannot download the expansion files or the user might have deleted previously downloaded expansion files. To handle these situations, your app must be able to download the files itself when the main activity starts, using a URL provided by Google Play .
The download process from a high level looks like this :

User selects to install your app from Google Play.

If Google Play is able to download the expansion files (which is the case for most
devices), it downloads them along with the APK.
If Google Play is unable to download the expansion files, it downloads the APK only .

When the user launches your app, your app must check whether the expansion files are
already saved on the device.

If yes, your app is ready to go.

If no, your app must download the expansion files over HTTP from Google Play. Your app
must send a request to the Google Play client using the Google Play’s app Licensing service, which
responds with the name, file size, and URL for each expansion file. With this information, you then
download the files and save them to the proper storage location.

Caution: It is critical that you include the necessary code to
download the expansion files from Google Play in the event that the files are not already on the
device when your app starts. As discussed in the following section about Downloading the Expansion Files, we’ve made a library available to you that
greatly simplifies this process and performs the download from a service with a minimal amount of
code from you.

Development checklist

Here’s a summary of the tasks you should perform to use expansion files with your app :

First determine whether your app’s compressed download size needs to be more than 100MB.
Space is precious and you should keep your total download size as small as possible. If your app
uses more than 100MB in order to provide multiple versions of your graphic assets for multiple screen
densities, consider instead publishing multiple APKs in which each APK
contains only the assets required for the screens that it targets. For the best results when
publishing to Google Play, upload an Android App Bundle, which
includes all your app’s compiled code and resources, but defers APK generation and signing to Google
Play.

Determine which app resources to separate from your APK and package them in a
file to use as the main expansion file.
Normally, you should only use the second patch expansion file when performing updates to the main expansion file. However, if your resources exceed the 2GB limit for the main expansion file, you can use the patch file for the rest of your assets .

Develop your app such that it uses the resources from your expansion files in the
device’s shared storage location.
Remember that you must not delete, move, or rename the expansion files .
If your app doesn’t demand a specific format, we suggest you create ZIP files for your expansion files, then read them using the APK Expansion Zip Library .

Add logic to your app’s main activity that checks whether the expansion files
are on the device upon start-up. If the files are not on the device, use Google Play’s app Licensing service to request URLs
for the expansion files, then download and save them.
To greatly reduce the amount of code you must write and ensure a good user experience during the download, we recommend you use the Downloader Library to implement your download behavior .
If you build your own download service instead of using the library, be aware that you must not change the name of the expansion files and must save them to the proper storage location .

Once you’ve finished your app development, follow the guide to Testing Your Expansion Files .

Rules and Limitations

Adding APK expansion files is a feature available when you upload your app using the Play Console. When uploading your app for the first time or updating an app that uses expansion files, you must be aware of the following rules and limitations :

Each expansion file can be no more than 2GB.

In order to download your expansion files from Google Play, the user must have
acquired your app from Google Play. Google Play will not
provide the URLs for your expansion files if the app was installed by other means.

When performing the download from within your app, the URL that Google Play
provides for each file is unique for every download and each one expires shortly after it is given
to your app.

If you update your app with a new APK or upload multiple APKs for the same
app, you can select expansion files that you’ve uploaded for a previous APK. The
expansion file’s name does not change—it retains the version received by the APK to
which the file was originally associated.

If you use expansion files in combination with multiple APKs in order to
provide different expansion files for different devices, you still must upload separate APKs
for each device in order to provide a unique versionCode
value and declare different filters for
each APK.

You cannot issue an update to your app by changing the expansion files
alone—you must upload a new APK to update your app. If your changes only
concern the assets in your expansion files, you can update your APK simply by changing the versionCode (and
perhaps also the versionName).

Do not save other data into your obb/
directory. If you must unpack some data, save it into the location specified by getExternalFilesDir().

Do not delete or rename the .obb expansion file (unless you’re
performing an update). Doing so will cause Google Play (or your app itself) to repeatedly
download the expansion file.

When updating an expansion file manually, you must delete the previous expansion file.

Downloading the Expansion Files

In most cases, Google Play downloads and saves your expansion files to the device at the same time it installs or updates the APK. This way, the expansion files are available when your app launches for the first time. However, in some cases your app must download the expansion files itself by requesting them from a URL provided to you in a response from Google Play’s app Licensing service .
The basic logic you need to download your expansion files is the following :

When your app starts, look for the expansion files on the shared storage location (in the
Android/obb// directory).

If the expansion files are there, you’re all set and your app can continue.

If the expansion files are not there:

Perform a request using Google Play’s app Licensing to get your
app’s expansion file names, sizes, and URLs.

Use the URLs provided by Google Play to download the expansion files and save
the expansion files. You must save the files to the shared storage location
(Android/obb//) and use the exact file name provided
by Google Play’s response.

Note: The URL that Google Play provides for your
expansion files is unique for every download and each one expires shortly after it is given to
your app.

If your app is không lấy phí ( not a paid app ), then you probably haven’t used the app Licensing service. It’s primarily designed for you to enforce licensing policies for your app and ensure that the user has the right to use your app ( he or she rightfully paid for it on Google Play ). In order to facilitate the expansion file functionality, the licensing service has been enhanced to provide a response to your app that includes the URL of your app’s expansion files that are hosted on Google Play. So, even if your app is không lấy phí for users, you need to include the License Verification Library ( LVL ) to use APK expansion files. Of course, if your app is không lấy phí, you don’t need to enforce license verification — you simply need the library to perform the request that returns the URL of your expansion files .

Note: Whether your app is free or not, Google Play
returns the expansion file URLs only if the user acquired your app from Google Play.

In addition to the LVL, you need a set of code that downloads the expansion files over an HTTP connection and saves them to the proper location on the device’s shared storage. As you build this procedure into your app, there are several issues you should take into consideration :

The device might not have enough space for the expansion files, so you should check
before beginning the download and warn the user if there’s not enough space.

File downloads should occur in a background service in order to avoid blocking the user
interaction and allow the user to leave your app while the download completes.

A variety of errors might occur during the request and download that you must
gracefully handle.

Network connectivity can change during the download, so you should handle such changes and
if interrupted, resume the download when possible.

While the download occurs in the background, you should provide a notification that
indicates the download progress, notifies the user when it’s done, and takes the user back to
your app when selected.

To simplify this work for you, we’ve built the Downloader Library, which requests the expansion file URLs through the licensing service, downloads the expansion files, performs all of the tasks listed above, and even allows your activity to pause and resume the download. By adding the Downloader Library and a few code hooks to your app, almost all the work to download the expansion files is already coded for you. As such, in order to provide the best user experience with minimal effort on your behalf, we recommend you use the Downloader Library to download your expansion files. The information in the following sections explain how to integrate the library into your app .

If you’d rather develop your own solution to download the expansion files using the Google
Play URLs, you must follow the app
Licensing documentation to perform a license request, then retrieve the expansion file names,
sizes, and URLs from the response extras. You should use the APKExpansionPolicy class (included in the License Verification Library) as your licensing
policy, which captures the expansion file names, sizes, and URLs from the licensing service..

About the Downloader Library

To use APK expansion files with your app and provide the best user experience with minimal effort on your behalf, we recommend you use the Downloader Library that’s included in the Google Play APK Expansion Library package. This library downloads your expansion files in a background service, shows a user notification with the download status, handles network connectivity loss, resumes the download when possible, and more .
To implement expansion file downloads using the Downloader Library, all you need to do is :

Extend a special Service subclass and BroadcastReceiver subclass that each require just a few
lines of code from you.

Add some logic to your main activity that checks whether the expansion files have
already been downloaded and, if not, invokes the download process and displays a
progress UI.

Implement a callback interface with a few methods in your main activity that
receives updates about the download progress.

The following sections explain how to set up your app using the Downloader Library .

Preparing to use the Downloader Library

To use the Downloader Library, you need to download two packages from the SDK Manager and add the appropriate libraries to your app .

First, open the Android SDK Manager
(Tools > SDK Manager), and under
Appearance & Behavior > System Settings > Android SDK, select
the SDK Tools tab to select and download:

Google Play Licensing Library package

Google Play APK Expansion Library package

Create a new library module for the License Verification Library and Downloader Library. For each library :

Select File > New > New Module.

In the Create New Module window, select Android Library,
and then select Next.

Specify an app/Library name such as “Google Play License Library”
and “Google Play Downloader Library”, choose Minimum SDK level, then select
Finish.

Select File > Project Structure.

Select the Properties tab and in Library
Repository, enter the library from the /extras/google/ directory
(play_licensing/ for the License Verification Library or play_apk_expansion/downloader_library/ for the Downloader Library).

Select OK to create the new module.

Note: The Downloader Library depends on the License
Verification Library. Be sure to add the License
Verification Library to the Downloader Library’s project properties.

Or, from a command line, update your project to include the libraries :
Change directories to the /tools/ directory.
Execute android update project with the --library option to add both the
LVL and the Downloader Library to your project. For example:
android update project --path ~/Android/MyApp \
--library ~/android_sdk/extras/google/market_licensing \
--library ~/android_sdk/extras/google/market_apk_expansion/downloader_library
With both the License Verification Library and Downloader Library added to your app, you’ll be able to quickly integrate the ability to download expansion files from Google Play. The format that you choose for the expansion files and how you read them from the shared storage is a separate implementation that you should consider based on your app needs .

Tip: The Apk Expansion package includes a sample
app
that shows how to use the Downloader Library in an app. The sample uses a third library
available in the Apk Expansion package called the APK Expansion Zip Library. If
you plan on
using ZIP files for your expansion files, we suggest you also add the APK Expansion Zip Library to
your app. For more information, see the section below
about Using the APK Expansion Zip Library.

Declaring user permissions

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

    
    

    
    

    
    

    
    

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

Implementing the downloader service

In order to perform downloads in the background, the Downloader Library provides its
own Service subclass called DownloaderService that you should extend. In
addition to downloading the expansion files for you, the DownloaderService also:

Registers a BroadcastReceiver that listens for changes to the
device’s network connectivity (the CONNECTIVITY_ACTION
broadcast) in order to pause the download when necessary (such as due to connectivity loss) and
resume the download when possible (connectivity is acquired).

Schedules an RTC_WAKEUP alarm to retry the download for
cases in which the service gets killed.

Builds a custom Notification that displays the download progress and
any errors or state changes.

Allows your app to manually pause and resume the download.

Verifies that the shared storage is mounted and available, that the files don’t already exist,
and that there is enough space, all before downloading the expansion files. Then notifies the user
if any of these are not true.

All you need to do is create a class in your app that extends the DownloaderService class and override three methods to provide specific app details:

getPublicKey()

This must return a string that is the Base64-encoded RSA public key for your publisher
account, available from the profile page on the Play Console (see Setting Up for Licensing).

getSALT()

This must return an array of random bytes that the licensing Policy uses to
create an Obfuscator. The salt ensures that your obfuscated SharedPreferences
file in which your licensing data is saved will be unique and non-discoverable.

getAlarmReceiverClassName()

This must return the class name of the BroadcastReceiver in
your app that should receive the alarm indicating that the download should be
restarted (which might happen if the downloader service unexpectedly stops).

For example, here’s a complete implementation of DownloaderService:

Kotlin
// You must use the public key belonging to your publisher account
const val BASE64_PUBLIC_KEY = "YourLVLKey"
// You should also modify this salt
val SALT = byteArrayOf(
        1, 42, -12, -1, 54, 98, -100, -12, 43, 2,
        -8, -4, 9, 5, -106, -107, -33, 45, -1, 84
)

class SampleDownloaderService : DownloaderService() {

    override fun getPublicKey(): String = BASE64_PUBLIC_KEY

    override fun getSALT(): ByteArray = SALT

    override fun getAlarmReceiverClassName(): String = SampleAlarmReceiver::class.java.name
}
Java
public class SampleDownloaderService extends DownloaderService {
    // You must use the public key belonging to your publisher account
    public static final String BASE64_PUBLIC_KEY = "YourLVLKey";
    // You should also modify this salt
    public static final byte[] SALT = new byte[] { 1, 42, -12, -1, 54, 98,
            -100, -12, 43, 2, -8, -4, 9, 5, -106, -107, -33, 45, -1, 84
    };

    @Override
    public String getPublicKey() {
        return BASE64_PUBLIC_KEY;
    }

    @Override
    public byte[] getSALT() {
        return SALT;
    }

    @Override
    public String getAlarmReceiverClassName() {
        return SampleAlarmReceiver.class.getName();
    }
}
Notice: You must update the BASE64_PUBLIC_KEY value
to be the public key belonging to your publisher account. You can find the key in the Developer
Console under your profile information. This is necessary even when testing
your downloads.

Remember to declare the service in your manifest file :
    
    ...
Implementing the alarm receiver

In order to monitor the progress of the file downloads and restart the download if necessary, the
DownloaderService schedules an RTC_WAKEUP alarm that
delivers an Intent to a BroadcastReceiver in your
app. You must define the BroadcastReceiver to call an API
from the Downloader Library that checks the status of the download and restarts
it if necessary.

You simply need to override the onReceive() method to call DownloaderClientMarshaller.startDownloadServiceIfRequired().

For example :

Kotlin
class SampleAlarmReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        try {
            DownloaderClientMarshaller.startDownloadServiceIfRequired(
                    context,
                    intent,
                    SampleDownloaderService::class.java
            )
        } catch (e: PackageManager.NameNotFoundException) {
            e.printStackTrace()
        }
    }
}
Java
public class SampleAlarmReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        try {
            DownloaderClientMarshaller.startDownloadServiceIfRequired(context,
                intent, SampleDownloaderService.class);
        } catch (NameNotFoundException e) {
            e.printStackTrace();
        }
    }
}
Notice that this is the class for which you must return the name
in your service’s getAlarmReceiverClassName() method (see the previous section).

Remember to declare the receiver in your manifest file:

Xem thêm: Định vị xe máy BK88M
    
    ...
Starting the download

The main activity in your app ( the one started by your launcher icon ) is responsible for verifying whether the expansion files are already on the device and initiating the download if they are not .
Starting the download using the Downloader Library requires the following procedures :
Check whether the files have been downloaded.
The Downloader Library includes some APIs in the Helper class to
help with this process:

getExpansionAPKFileName(Context, c, boolean mainFile, int versionCode)

doesFileExist(Context c, String fileName, long fileSize)

For example, the sample app provided in the Apk Expansion package calls the
following method in the activity’s onCreate() method to check
whether the expansion files already exist on the device:

Kotlin
fun expansionFilesDelivered(): Boolean {
    xAPKS.forEach { xf ->
        Helpers.getExpansionAPKFileName(this, xf.isBase, xf.fileVersion).also { fileName ->
            if (!Helpers.doesFileExist(this, fileName, xf.fileSize, false))
                return false
        }
    }
    return true
}
Java
boolean expansionFilesDelivered() {
    for (XAPKFile xf : xAPKS) {
        String fileName = Helpers.getExpansionAPKFileName(this, xf.isBase,
            xf.fileVersion);
        if (!Helpers.doesFileExist(this, fileName, xf.fileSize, false))
            return false;
    }
    return true;
}
In this case, each XAPKFile object holds the version number and file size of a known
expansion file and a boolean as to whether it’s the main expansion file. (See the sample
app’s SampleDownloaderActivity class for details.)

If this method returns false, then the app must begin the download .
Start the download by calling the static method DownloaderClientMarshaller.startDownloadServiceIfRequired(Context c, PendingIntent notificationClient, Class serviceClass).
The method takes the following parameters :

context: Your app’s Context.

notificationClient: A PendingIntent to start your main
activity. This is used in the Notification that the DownloaderService
creates to show the download progress. When the user selects the notification, the system
invokes the PendingIntent you supply here and should open the activity
that shows the download progress (usually the same activity that started the download).

serviceClass: The Class object for your implementation of
DownloaderService, required to start the service and begin the download if necessary.

The method returns an integer that indicates whether or not the download is required. Possible values are :

NO_DOWNLOAD_REQUIRED: Returned if the files already
exist or a download is already in progress.

LVL_CHECK_REQUIRED: Returned if a license verification is
required in order to acquire the expansion file URLs.

DOWNLOAD_REQUIRED: Returned if the expansion file URLs are already known,
but have not been downloaded.

The behavior for LVL_CHECK_REQUIRED and DOWNLOAD_REQUIRED are essentially the
same and you normally don’t need to be concerned about them. In your main activity that calls startDownloadServiceIfRequired(), you can simply check whether or not the response is NO_DOWNLOAD_REQUIRED. If the response is anything other than NO_DOWNLOAD_REQUIRED,
the Downloader Library begins the download and you should update your activity UI to
display the download progress (see the next step). If the response is NO_DOWNLOAD_REQUIRED, then the files are available and your app can start.

For example :

Kotlin
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    // Check if expansion files are available before going any further
    if (!expansionFilesDelivered()) {
        val pendingIntent =
                // Build an Intent to start this activity from the Notification
                Intent(this, MainActivity::class.java).apply {
                    flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP
                }.let { notifierIntent ->
                    PendingIntent.getActivity(
                            this,
                            0,
                            notifierIntent,
                            PendingIntent.FLAG_UPDATE_CURRENT
                    )
                }


        // Start the download service (if required)
        val startResult: Int = DownloaderClientMarshaller.startDownloadServiceIfRequired(
                this,
                pendingIntent,
                SampleDownloaderService::class.java
        )
        // If download has started, initialize this activity to show
        // download progress
        if (startResult != DownloaderClientMarshaller.NO_DOWNLOAD_REQUIRED) {
            // This is where you do set up to display the download
            // progress (next step)
            ...
            return
        } // If the download wasn't necessary, fall through to start the app
    }
    startApp() // Expansion files are available, start the app
}
Java
@Override
public void onCreate(Bundle savedInstanceState) {
    // Check if expansion files are available before going any further
    if (!expansionFilesDelivered()) {
        // Build an Intent to start this activity from the Notification
        Intent notifierIntent = new Intent(this, MainActivity.getClass());
        notifierIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
                                Intent.FLAG_ACTIVITY_CLEAR_TOP);
        ...
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0,
                notifierIntent, PendingIntent.FLAG_UPDATE_CURRENT);

        // Start the download service (if required)
        int startResult =
            DownloaderClientMarshaller.startDownloadServiceIfRequired(this,
                        pendingIntent, SampleDownloaderService.class);
        // If download has started, initialize this activity to show
        // download progress
        if (startResult != DownloaderClientMarshaller.NO_DOWNLOAD_REQUIRED) {
            // This is where you do set up to display the download
            // progress (next step)
            ...
            return;
        } // If the download wasn't necessary, fall through to start the app
    }
    startApp(); // Expansion files are available, start the app
}
When the startDownloadServiceIfRequired() method returns anything other
than NO_DOWNLOAD_REQUIRED, create an instance of IStub by
calling DownloaderClientMarshaller.CreateStub(IDownloaderClient client, Class downloaderService). The IStub provides a binding between your activity to the downloader
service such that your activity receives callbacks about the download progress.

In order to instantiate your IStub by calling CreateStub(), you must pass it
an implementation of the IDownloaderClient interface and your DownloaderService
implementation. The next section about Receiving download progress discusses
the IDownloaderClient interface, which you should usually implement in your Activity class so you can update the activity UI when the download state changes.

We recommend that you call CreateStub() to instantiate your IStub during your activity’s onCreate() method, after startDownloadServiceIfRequired()
starts the download.

For example, in the previous code sample for onCreate(), you can respond to the startDownloadServiceIfRequired() result like this:

Kotlin
        // Start the download service (if required)
        val startResult = DownloaderClientMarshaller.startDownloadServiceIfRequired(
                this@MainActivity,
                pendingIntent,
                SampleDownloaderService::class.java
        )
        // If download has started, initialize activity to show progress
        if (startResult != DownloaderClientMarshaller.NO_DOWNLOAD_REQUIRED) {
            // Instantiate a member instance of IStub
            downloaderClientStub =
                    DownloaderClientMarshaller.CreateStub(this, SampleDownloaderService::class.java)
            // Inflate layout that shows download progress
            setContentView(R.layout.downloader_ui)
            return
        }
Java
        // Start the download service (if required)
        int startResult =
            DownloaderClientMarshaller.startDownloadServiceIfRequired(this,
                        pendingIntent, SampleDownloaderService.class);
        // If download has started, initialize activity to show progress
        if (startResult != DownloaderClientMarshaller.NO_DOWNLOAD_REQUIRED) {
            // Instantiate a member instance of IStub
            downloaderClientStub = DownloaderClientMarshaller.CreateStub(this,
                    SampleDownloaderService.class);
            // Inflate layout that shows download progress
            setContentView(R.layout.downloader_ui);
            return;
        }
After the onCreate() method returns, your activity
receives a call to onResume(), which is where you should then
call connect() on the IStub, passing it your app’s Context. Conversely, you should call
disconnect() in your activity’s onStop() callback.

Kotlin
override fun onResume() {
    downloaderClientStub?.connect(this)
    super.onResume()
}

override fun onStop() {
    downloaderClientStub?.disconnect(this)
    super.onStop()
}
Java
@Override
protected void onResume() {
    if (null != downloaderClientStub) {
        downloaderClientStub.connect(this);
    }
    super.onResume();
}

@Override
protected void onStop() {
    if (null != downloaderClientStub) {
        downloaderClientStub.disconnect(this);
    }
    super.onStop();
}
Calling connect() on the IStub binds your activity to the DownloaderService such that your activity receives callbacks regarding changes to the download
state through the IDownloaderClient interface.
Receiving download progress

To receive updates regarding the download progress and to interact with the DownloaderService, you must implement the Downloader Library’s IDownloaderClient interface.
Usually, the activity you use to start the download should implement this interface in order to
display the download progress and send requests to the service.

The required interface methods for IDownloaderClient are:
onServiceConnected(Messenger m)
After you instantiate the IStub in your activity, you’ll receive a call to this
method, which passes a Messenger object that’s connected with your instance
of DownloaderService. To send requests to the service, such as to pause and resume
downloads, you must call DownloaderServiceMarshaller.CreateProxy() to receive the IDownloaderService interface connected to the service.
A recommended implementation looks like this :

Kotlin
private var remoteService: IDownloaderService? = null
...

override fun onServiceConnected(m: Messenger) {
    remoteService = DownloaderServiceMarshaller.CreateProxy(m).apply {
        downloaderClientStub?.messenger?.also { messenger ->
            onClientUpdated(messenger)
        }
    }
}
Java
private IDownloaderService remoteService;
...

@Override
public void onServiceConnected(Messenger m) {
    remoteService = DownloaderServiceMarshaller.CreateProxy(m);
    remoteService.onClientUpdated(downloaderClientStub.getMessenger());
}
With the IDownloaderService object initialized, you can send commands to the
downloader service, such as to pause and resume the download (requestPauseDownload()
and requestContinueDownload()).
onDownloadStateChanged(int newState)

The download service calls this when a change in download state occurs, such as the
download begins or completes.

The newState value will be one of several possible values specified in
by one of the IDownloaderClient class’s STATE_* constants.

To provide a useful message to your users, you can request a corresponding string
for each state by calling Helpers.getDownloaderStringResourceIDFromState(). This
returns the resource ID for one of the strings bundled with the Downloader
Library. For example, the string “Download paused because you are roaming” corresponds to STATE_PAUSED_ROAMING.

onDownloadProgress(DownloadProgressInfo progress)

The download service calls this to deliver a DownloadProgressInfo object,
which describes various information about the download progress, including estimated time remaining,
current speed, overall progress, and total so you can update the download progress UI.
Tip: For examples of these callbacks that update the download
progress UI, see the SampleDownloaderActivity in the sample app provided with the
Apk Expansion package.

Some public methods for the IDownloaderService interface you might find useful are:
requestPauseDownload()

Pauses the download.

requestContinueDownload()

Resumes a paused download.

setDownloadFlags(int flags)
Sets user preferences for network types on which its OK to download the files. The
current implementation supports one flag, FLAGS_DOWNLOAD_OVER_CELLULAR, but you can add
others. By default, this flag is not enabled, so the user must be on Wi-Fi to download
expansion files. You might want to provide a user preference to enable downloads over
the cellular network. In which case, you can call:

Kotlin
remoteService = DownloaderServiceMarshaller.CreateProxy(m).apply {
    ...
    setDownloadFlags(IDownloaderService.FLAGS_DOWNLOAD_OVER_CELLULAR)
}
Java
remoteService
    .setDownloadFlags(IDownloaderService.FLAGS_DOWNLOAD_OVER_CELLULAR);
Using APKExpansionPolicy

If you decide to build your own downloader service instead of using the Google Play
Downloader Library, you should still use the APKExpansionPolicy that’s provided in the License Verification Library. The APKExpansionPolicy class is nearly identical to ServerManagedPolicy (available in the
Google Play License Verification Library) but includes additional handling for the APK expansion
file response extras.

Note: If you do use the Downloader Library as discussed in the previous section, the
library performs all interaction with the APKExpansionPolicy so you don’t have to use
this class directly.

The class includes methods to help you get the necessary information about the available expansion files :

getExpansionURLCount()

getExpansionURL(int index)

getExpansionFileName(int index)

getExpansionFileSize(int index)

For more information about how to use the APKExpansionPolicy when you’re not
using the Downloader Library, see the documentation for Adding Licensing to Your App,
which explains how to implement a license policy such as this one.

Reading the Expansion File

Once your APK expansion files are saved on the device, how you read your files
depends on the type of file you’ve used. As discussed in the overview, your
expansion files can be any kind of file you
want, but are renamed using a particular file name format and are saved to
/Android/obb//.

Regardless of how you read your files, you should always first check that the external storage is available for reading. There’s a chance that the user has the storage mounted to a computer over USB or has actually removed the SD card .

Note: When your app starts, you should always check whether
the external storage space is available and readable by calling getExternalStorageState(). This returns one of several possible strings
that represent the state of the external storage. In order for it to be readable by your
app, the return value must be MEDIA_MOUNTED.

Getting the file names

As described in the overview, your APK expansion files are saved using a specific file name format :
[main|patch]...obb
To get the location and names of your expansion files, you should use the
getExternalStorageDirectory() and getPackageName() methods to construct the path to your files.

Here’s a method you can use in your app to get an array containing the complete path to both your expansion files :

Kotlin
fun getAPKExpansionFiles(ctx: Context, mainVersion: Int, patchVersion: Int): Array {
    val packageName = ctx.packageName
    val ret = mutableListOf()
    if (Environment.getExternalStorageState() == Environment.MEDIA_MOUNTED) {
        // Build the full path to the app's expansion files
        val root = Environment.getExternalStorageDirectory()
        val expPath = File(root.toString() + EXP_PATH + packageName)

        // Check that expansion file path exists
        if (expPath.exists()) {
            if (mainVersion > 0) {
                val strMainPath = "$expPath${File.separator}main.$mainVersion.$packageName.obb"
                val main = File(strMainPath)
                if (main.isFile) {
                    ret += strMainPath
                }
            }
            if (patchVersion > 0) {
                val strPatchPath = "$expPath${File.separator}patch.$mainVersion.$packageName.obb"
                val main = File(strPatchPath)
                if (main.isFile) {
                    ret += strPatchPath
                }
            }
        }
    }
    return ret.toTypedArray()
}
Java
// The shared path to all app expansion files
private final static String EXP_PATH = "/Android/obb/";

static String[] getAPKExpansionFiles(Context ctx, int mainVersion,
      int patchVersion) {
    String packageName = ctx.getPackageName();
    Vector ret = new Vector();
    if (Environment.getExternalStorageState()
          .equals(Environment.MEDIA_MOUNTED)) {
        // Build the full path to the app's expansion files
        File root = Environment.getExternalStorageDirectory();
        File expPath = new File(root.toString() + EXP_PATH + packageName);

        // Check that expansion file path exists
        if (expPath.exists()) {
            if ( mainVersion > 0 ) {
                String strMainPath = expPath + File.separator + "main." +
                        mainVersion + "." + packageName + ".obb";
                File main = new File(strMainPath);
                if ( main.isFile() ) {
                        ret.add(strMainPath);
                }
            }
            if ( patchVersion > 0 ) {
                String strPatchPath = expPath + File.separator + "patch." +
                        mainVersion + "." + packageName + ".obb";
                File main = new File(strPatchPath);
                if ( main.isFile() ) {
                        ret.add(strPatchPath);
                }
            }
        }
    }
    String[] retArray = new String[ret.size()];
    ret.toArray(retArray);
    return retArray;
}
You can call this method by passing it your app Context
and the desired expansion file’s version.

There are many ways you could determine the expansion file version number. One simple way is to
save the version in a SharedPreferences file when the download begins, by
querying the expansion file name with the APKExpansionPolicy class’s getExpansionFileName(int index) method. You can then get the version code by reading the SharedPreferences file when you want to access the expansion
file.

For more information about reading from the shared storage, see the Data Storage documentation .

Using the APK Expansion Zip Library

The Google Market Apk Expansion package includes a library called the APK
Expansion Zip Library (located in /extras/google/google_market_apk_expansion/zip_file/). This is an optional library that
helps you read your expansion
files when they’re saved as ZIP files. Using this library allows you to easily read resources from
your ZIP expansion files as a virtual file system.

The APK Expansion Zip Library includes the following classes and APIs :

APKExpansionSupport

Provides some methods to access expansion file names and ZIP files:

getAPKExpansionFiles()

The same method shown above that returns the complete file path to both expansion
files.

getAPKExpansionZipFile(Context ctx, int mainVersion, int patchVersion)

Returns a ZipResourceFile representing the sum of both the main file and
patch file. That is, if you specify both the mainVersion and the
patchVersion, this returns a ZipResourceFile that provides read access to
all the data, with the patch file’s data merged on top of the main file.

ZipResourceFile

Represents a ZIP file on the shared storage and performs all the work to provide a virtual
file system based on your ZIP files. You can get an instance using APKExpansionSupport.getAPKExpansionZipFile() or with the ZipResourceFile by passing it the
path to your expansion file. This class includes a variety of useful methods, but you generally
don’t need to access most of them. A couple of important methods are:

getInputStream(String assetPath)

Provides an InputStream to read a file within the ZIP file. The
assetPath must be the path to the desired file, relative to
the root of the ZIP file contents.

getAssetFileDescriptor(String assetPath)

Provides an AssetFileDescriptor for a file within the
ZIP file. The assetPath must be the path to the desired file, relative to
the root of the ZIP file contents. This is useful for certain Android APIs that require an AssetFileDescriptor, such as some MediaPlayer APIs.

APEZProvider

Most apps don’t need to use this class. This class defines a ContentProvider that marshals the data from the ZIP files through a content
provider Uri in order to provide file access for certain Android APIs that
expect Uri access to media files. For example, this is useful if you want to
play a video with VideoView.setVideoURI().

Skipping ZIP compression of media files

If you’re using your expansion files to store media files, a ZIP file still allows you to
use Android media playback calls that provide offset and length controls (such as MediaPlayer.setDataSource() and
SoundPool.load()). In order for
this to work, you must not perform additional compression on the media files when creating the ZIP
packages. For example, when using the zip tool, you should use the -n
option to specify the file suffixes that should not be compressed:

zip -n .mp4;.ogg main_expansion media_files

Reading from a ZIP file

When using the APK Expansion Zip Library, reading a file from your ZIP usually requires the following :

Kotlin
// Get a ZipResourceFile representing a merger of both the main and patch files
val expansionFile =
        APKExpansionSupport.getAPKExpansionZipFile(appContext, mainVersion, patchVersion)

// Get an input stream for a known file inside the expansion file ZIPs
expansionFile.getInputStream(pathToFileInsideZip).use {
    ...
}
Java
// Get a ZipResourceFile representing a merger of both the main and patch files
ZipResourceFile expansionFile =
    APKExpansionSupport.getAPKExpansionZipFile(appContext,
        mainVersion, patchVersion);

// Get an input stream for a known file inside the expansion file ZIPs
InputStream fileStream = expansionFile.getInputStream(pathToFileInsideZip);
The above code provides access to any file that exists in either your main expansion file or
patch expansion file, by reading from a merged map of all the files from both files. All you
need to provide the getAPKExpansionFile() method is your app android.content.Context and the version number for both the main expansion file and patch
expansion file.

If you’d rather read from a specific expansion file, you can use the ZipResourceFile constructor with the path to the desired expansion file:

Kotlin
// Get a ZipResourceFile representing a specific expansion file
val expansionFile = ZipResourceFile(filePathToMyZip)

// Get an input stream for a known file inside the expansion file ZIPs
expansionFile.getInputStream(pathToFileInsideZip).use {
    ...
}
Java
// Get a ZipResourceFile representing a specific expansion file
ZipResourceFile expansionFile = new ZipResourceFile(filePathToMyZip);

// Get an input stream for a known file inside the expansion file ZIPs
InputStream fileStream = expansionFile.getInputStream(pathToFileInsideZip);
For more information about using this library for your expansion files, look at
the sample app’s SampleDownloaderActivity class, which includes additional code to
verify the downloaded files using CRC. Beware that if you use this sample as the basis for
your own implementation, it requires that you declare the byte size of your expansion
files in the xAPKS array.

Testing Your Expansion Files

Before publishing your app, there are two things you should test : Reading the expansion files and downloading the files .

Testing file reads

Before you upload your app to Google Play, you should test your app’s ability to read the files from the shared storage. All you need to do is add the files to the appropriate location on the device shared storage and launch your app :

On your device, create the appropriate directory on the shared storage where Google
Play will save your files.

For example, if your package name is com.example.android, you need to create
the directory Android/obb/com.example.android/ on the shared storage space. (Plug in
your test device to your computer to mount the shared storage and manually create this
directory.)

Manually add the expansion files to that directory. Be sure that you rename your files to
match the file name format that Google Play will use.

For example, regardless of the file type, the main expansion file for the com.example.android app should be main.0300110.com.example.android.obb.
The version code can be whatever value you want. Just remember:

The main expansion file always starts with main and the patch file starts with
patch.

The package name always matches that of the APK to which the file is attached on
Google Play.

Now that the expansion file(s) are on the device, you can install and run your app to
test your expansion file(s).

Here are some reminders about handling the expansion files :

Do not delete or rename the .obb expansion files (even if you unpack
the data to a different location). Doing so will cause Google Play (or your app itself) to
repeatedly download the expansion file.

Do not save other data into your obb/
directory. If you must unpack some data, save it into the location specified by getExternalFilesDir().

Testing file downloads

Because your app must sometimes manually download the expansion files when it first opens, it’s important that you test this process to be sure your app can successfully query for the URLs, download the files, and save them to the device .
To test your app’s implementation of the manual download procedure, you can publish it to the internal test track, so it’s only available to authorized testers. If everything works as expected, your app should begin downloading the expansion files as soon as the main activity starts .

Note: Previously you could test an app by
uploading an unpublished “draft” version. This functionality is no longer
supported. Instead, you must publish it to an internal, closed, or open testing
track. For more information, see
Draft Apps are No
Longer Supported.

Updating Your app

One of the great benefits to using expansion files on Google Play is the ability to update your app without re-downloading all of the original assets. Because Google Play allows you to provide two expansion files with each APK, you can use the second file as a ” patch ” that provides updates and new assets. Doing so avoids the need to re-download the main expansion file which could be large and expensive for users .
The patch expansion file is technically the same as the main expansion file and neither the Android system nor Google Play perform actual patching between your main and patch expansion files. Your app code must perform any necessary patches itself .

If you use ZIP files as your expansion files, the APK Expansion Zip
Library that’s included with the Apk Expansion package includes the ability to merge
your
patch file with the main expansion file.

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Note: Even if you only need to make changes to the patch
expansion file, you must still update the APK in order for Google Play to perform an update.
If you don’t require code changes in the app, you should simply update the versionCode in the
manifest.

As long as you don’t change the main expansion file that’s associated with the APK in the Play Console, users who previously installed your app will not download the main expansion file. Existing users receive only the updated APK and the new patch expansion file ( retaining the previous main expansion file ) .

Here are a few issues to keep in mind regarding updates to expansion files :

There can be only two expansion files for your app at a time. One main expansion
file and one patch expansion file. During an update to a file, Google Play deletes the
previous version (and so must your app when performing manual updates).
When adding a patch expansion file, the Android system does not actually patch your
app or main expansion file. You must design your app to support the patch data.
However, the Apk Expansion package includes a library for using ZIP files
as expansion files, which merges the data from the patch file into the main expansion file so
you can easily read all the expansion file data.

Source: https://thomaygiat.com
Category : Ứng Dụng

APK Expansion Files | Android Developers

APK Expansion Files | Android Developers

Overview

File name format

Storage location

Kotlin

Java

Download process

Development checklist

Rules and Limitations

Downloading the Expansion Files

About the Downloader Library

Preparing to use the Downloader Library

Declaring user permissions

Implementing the downloader service

Kotlin

Java

Implementing the alarm receiver

Kotlin

Java

Starting the download

Kotlin

Java

Kotlin

Java

Kotlin

Java

Kotlin

Java

Receiving download progress

Kotlin

Java

Kotlin

Java

Using APKExpansionPolicy

Reading the Expansion File

Getting the file names

Kotlin

Java

Using the APK Expansion Zip Library

Skipping ZIP compression of media files

Reading from a ZIP file

Kotlin

Java

Kotlin

Java

Testing Your Expansion Files

Testing file reads

Testing file downloads

Updating Your app

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