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.
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 use the Downloader Library, you need to download two packages from the SDK Manager and add the appropriate libraries to your app. For each 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. 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:. 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:. 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:.
For example, here's a complete implementation of DownloaderService :. You can find the key in the Developer Console under your profile information. This is necessary even when testing your downloads. 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. Notice that this is the class for which you must return the name in your service's getAlarmReceiverClassName method see the previous section. 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.
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:. 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. The method returns an integer that indicates whether or not the download is required. Possible values are:.
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. For example, in the previous code sample for onCreate , you can respond to the startDownloadServiceIfRequired result like this:.
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. 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. 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.
With the IDownloaderService object initialized, you can send commands to the downloader service, such as to pause and resume the download requestPauseDownload and requestContinueDownload. To provide a useful message to your users, you can request a corresponding string for each state by calling Helpers.
This returns the resource ID for one of the strings bundled with the Downloader Library. 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:.
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:. 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.
Once your APK expansion files are saved on the device, how you read your files depends on the type of file you've used. 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. As described in the overview , your APK expansion files are saved using a specific file name format:. 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:. 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. 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. 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.
For example, when using the zip tool, you should use the -n option to specify the file suffixes that should not be compressed:. 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.
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:. 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. Before publishing your app, there are two things you should test: Reading the expansion files and downloading the files.
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:. For example, if your package name is com. Plug in your test device to your computer to mount the shared storage and manually create this directory. For example, regardless of the file type, the main expansion file for the com. The version code can be whatever value you want. Just remember:. 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.
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. Now you need to install an APK file on your device.
You need to follow the following procedures to download an APK file:. Follow the steps below and find out more about OBB files. Now you know the twist and turns of the opening process.
There are some points that you have to remember further. First of all, try to understand the size of your compressed file. If the app that you are using utilizes greater space than MB, then you can publish several APK files. To locate OBB files, the easiest way is to use an advanced file browser.
Please go to Android system settings, find storage section, click it. The answer is no. The only time the OBB file gets deleted is when the user uninstalls the app.
Or when the app deletes the file itself. On a side note, which I happened to find out only later, if you delete or rename your OBB file, it gets re-downloaded every time you release an app update.
Use the three-dot menu button to select New Folder, then name this folder obb. This extension is like any other file that comes with a set of files these three or four characters that fall at the end of the name File that allows the operating system to recognize different formats and choose the program or application needed to open the file.
The answer to the question above is what kind of data is contained in the OBB files? These files serve as a memory to store additional information for games and Android apps embedded on your smartphone.
This means that it is not a place to store your personal information or data; it is only intended to store the maps or levels you have reached in the game What's on a machine. So it's important to clarify that OBB files are the app or game itself, but they only contain the relevant data that the game needs to function properly.
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