Implementing Freemium
Before you can start using the In-app Billing service, you'll need to add the library that contains the In-app Billing Version 3 API to your Android project. You also need to set the permissions for your application to communicate with Google Play. In addition, you'll need to establish a connection between your application and Google Play. You should also verify that the In-app Billing API version that you are using in your application is supported by Google Play.
In this training class, you will use a reference implementation for the In-app Billing Version 3 API called the {@code TrivialDrive} sample application. The sample includes convenience classes to quickly set up the In-app Billing service, marshal and unmarshal data types, and handle In-app Billing requests from the main thread of your application.
To download the sample application:
Alternatively, you can use {@code git} to manually clone the repository from https://github.com/googlesamples/android-play-billing
The Google Play Developer Console is where you publish your In-app Billing application and manage the various digital goods that are available for purchase from your application. When you create a new application entry in the Developer Console, it automatically generates a public license key for your application. You will need this key to establish a trusted connection from your application to the Google Play servers. You only need to generate this key once per application, and don’t need to repeat these steps when you update the APK file for your application.
To add your application to the Developer Console:
Your application should now appear in the list of applications in Developer Console.
To use the In-app Billing Version 3 features, you must add the {@code IInAppBillingService.aidl} file to your Android project. This Android Interface Definition Language (AIDL) file defines the interface to the Google Play service.
You can find the {@code IInAppBillingService.aidl} file in the provided sample app. Depending on whether you are creating a new application or modifying an existing application, follow the instructions below to add the In-app Billing Library to your project.
To add the In-app Billing Version 3 library to your new In-app Billing project:
To add the In-app Billing Version 3 library to your existing In-app Billing project:
Your project should now contain the In-app Billing Version 3 library.
Your app needs to have permission to communicate request and response messages to the Google Play’s billing service. To give your app the necessary permission, add this line in your {@code AndroidManifest.xml} manifest file:
<uses-permission android:name="com.android.vending.BILLING" />
You must bind your Activity to Google Play’s In-app Billing service to send In-app Billing requests to Google Play from your application. The convenience classes provided in the sample handles the binding to the In-app Billing service, so you don’t have to manage the network connection directly.
To set up synchronous communication with Google Play, create an {@code IabHelper} instance in your activity's {@code onCreate} method. In the constructor, pass in the {@code Context} for the activity, along with a string containing the public license key that was generated earlier by the Google Play Developer Console.
Security Recommendation: It is highly recommended that you do not hard-code the exact public license key string value as provided by Google Play. Instead, you can construct the whole public license key string at runtime from substrings, or retrieve it from an encrypted store, before passing it to the constructor. This approach makes it more difficult for malicious third-parties to modify the public license key string in your APK file.
IabHelper mHelper;
@Override
public void onCreate(Bundle savedInstanceState) {
// ...
String base64EncodedPublicKey;
// compute your public key and store it in base64EncodedPublicKey
mHelper = new IabHelper(this, base64EncodedPublicKey);
}
Next, perform the service binding by calling the {@code startSetup} method on the {@code IabHelper} instance that you created. Pass the method an {@code OnIabSetupFinishedListener} instance, which is called once the {@code IabHelper} completes the asynchronous setup operation. As part of the setup process, the {@code IabHelper} also checks if the In-app Billing Version 3 API is supported by Google Play. If the API version is not supported, or if an error occured while establishing the service binding, the listener is notified and passed an {@code IabResult} object with the error message.
mHelper.startSetup(new IabHelper.OnIabSetupFinishedListener() {
public void onIabSetupFinished(IabResult result) {
if (!result.isSuccess()) {
// Oh noes, there was a problem.
Log.d(TAG, "Problem setting up In-app Billing: " + result);
}
// Hooray, IAB is fully set up!
}
});
If the setup completed successfully, you can now use the {@code mHelper} reference to communicate with the Google Play service. When your application is launched, it is a good practice to query Google Play to find out what in-app items are owned by a user. This is covered further in the Query Purchased Items section.
Important: Remember to unbind from the In-app Billing service when you are done with your activity. If you don’t unbind, the open service connection could cause your device’s performance to degrade. To unbind and free your system resources, call the {@code IabHelper}'s {@code dispose} method when your {@code Activity} is destroyed.
@Override
public void onDestroy() {
super.onDestroy();
if (mHelper != null) mHelper.dispose();
mHelper = null;
}