Implementing In-app Billing

In-app Billing on Google Play provides a straightforward, simple interface for sending In-app Billing requests and managing In-app Billing transactions using Google Play. The information below covers the basics of how to make calls from your application to the In-app Billing service using the Version 3 API.

Note: To see a complete implementation and learn how to test your application, see the Selling In-app Products training class. The training class provides a complete sample In-app Billing application, including convenience classes to handle key tasks related to setting up your connection, sending billing requests and processing responses from Google Play, and managing background threading so that you can make In-app Billing calls from your main activity.

Before you start, be sure that you read the In-app Billing Overview to familiarize yourself with concepts that will make it easier for you to implement In-app Billing.

To implement In-app Billing in your application, you need to do the following:

  1. Add the In-app Billing library to your project.
  2. Update your AndroidManifest.xml file.
  3. Create a ServiceConnection and bind it to IInAppBillingService.
  4. Send In-app Billing requests from your application to IInAppBillingService.
  5. Handle In-app Billing responses from Google Play.

Adding the AIDL file to your project

IInAppBillingService.aidl is an Android Interface Definition Language (AIDL) file that defines the interface to the In-app Billing Version 3 service. You will use this interface to make billing requests by invoking IPC method calls.

To get the AIDL file:

  1. Open the Android SDK Manager.
  2. In the SDK Manager, expand the Extras section.
  3. Select Google Play Billing Library.
  4. Click Install packages to complete the download.

The IInAppBillingService.aidl file will be installed to <sdk>/extras/google/play_billing/.

To add the AIDL to your project:

  1. Copy the IInAppBillingService.aidl file to your Android project.
    • If you are using Eclipse:
      1. If you are starting from an existing Android project, open the project in Eclipse. If you are creating a new Android project from scratch, click File > New > Android Application Project, then follow the instructions in the New Android Application wizard to create a new project in your workspace.
      2. In the /src directory, click File > New > Package, then create a package named com.android.vending.billing.
      3. Copy the IInAppBillingService.aidl file from <sdk>/extras/google/play_billing/ and paste it into the src/com.android.vending.billing/ folder in your workspace.
    • If you are developing in a non-Eclipse environment: Create the following directory /src/com/android/vending/billing and copy the IInAppBillingService.aidl file into this directory. Put the AIDL file into your project and use the Ant tool to build your project so that the IInAppBillingService.java file gets generated.
  2. Build your application. You should see a generated file named IInAppBillingService.java in the /gen directory of your project.

Updating Your Application's Manifest

In-app billing relies on the Google Play application, which handles all communication between your application and the Google Play server. To use the Google Play application, your application must request the proper permission. You can do this by adding the com.android.vending.BILLING permission to your AndroidManifest.xml file. If your application does not declare the In-app Billing permission, but attempts to send billing requests, Google Play will refuse the requests and respond with an error.

To give your app the necessary permission, add this line in your Android.xml manifest file:

<uses-permission android:name="com.android.vending.BILLING" />

Creating a ServiceConnection

Your application must have a ServiceConnection to facilitate messaging between your application and Google Play. At a minimum, your application must do the following:

  • Bind to IInAppBillingService.
  • Send billing requests (as IPC method calls) to the Google Play application.
  • Handle the synchronous response messages that are returned with each billing request.

Binding to IInAppBillingService

To establish a connection with the In-app Billing service on Google Play, implement a ServiceConnection to bind your activity to IInAppBillingService. Override the onServiceDisconnected and onServiceConnected methods to get a reference to the IInAppBillingService instance after a connection has been established.

IInAppBillingService mService;

ServiceConnection mServiceConn = new ServiceConnection() {
   @Override
   public void onServiceDisconnected(ComponentName name) {
       mService = null;
   }

   @Override
   public void onServiceConnected(ComponentName name, 
      IBinder service) {
       mService = IInAppBillingService.Stub.asInterface(service);
   }
};

In your activity’s onCreate method, perform the binding by calling the bindService method. Pass the method an Intent that references the In-app Billing service and an instance of the ServiceConnection that you created, and explicitly set the Intent's target package name to com.android.vending — the package name of Google Play app.

Caution: To protect the security of billing transactions, always make sure to explicitly set the intent's target package name to com.android.vending, using setPackage() as shown in the example below. Setting the package name explicitly ensures that only the Google Play app can handle billing requests from your app, preventing other apps from intercepting those requests.

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  Intent serviceIntent = new Intent("com.android.vending.billing.InAppBillingService.BIND");
  serviceIntent.setPackage("com.android.vending");
  bindService(serviceIntent, mServiceConn, Context.BIND_AUTO_CREATE);

You can now use the mService reference to communicate with the Google Play service.

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. This example shows how to perform the unbind operation on a service connection to In-app Billing called mServiceConn by overriding the activity’s onDestroy method.

@Override
public void onDestroy() {
    super.onDestroy();
    if (mService != null) {
        unbindService(mServiceConn);
    }	
}

For a complete implementation of a service connection that binds to the IInAppBillingService, see the Selling In-app Products training class and associated sample.

Making In-app Billing Requests

Once your application is connected to Google Play, you can initiate purchase requests for in-app products. Google Play provides a checkout interface for users to enter their payment method, so your application does not need to handle payment transactions directly. When an item is purchased, Google Play recognizes that the user has ownership of that item and prevents the user from purchasing another item with the same product ID until it is consumed. You can control how the item is consumed in your application, and notify Google Play to make the item available for purchase again. You can also query Google Play to quickly retrieve the list of purchases that were made by the user. This is useful, for example, when you want to restore the user's purchases when your user launches your app.

Querying for Items Available for Purchase

In your application, you can query the item details from Google Play using the In-app Billing Version 3 API. To pass a request to the In-app Billing service, first create a Bundle that contains a String ArrayList of product IDs with key "ITEM_ID_LIST", where each string is a product ID for an purchasable item.

ArrayList<String> skuList = new ArrayList<String> ();
skuList.add("premiumUpgrade");
skuList.add("gas");
Bundle querySkus = new Bundle();
querySkus.putStringArrayList(“ITEM_ID_LIST”, skuList);

To retrieve this information from Google Play, call the getSkuDetails method on the In-app Billing Version 3 API, and pass the method the In-app Billing API version (“3”), the package name of your calling app, the purchase type (“inapp”), and the Bundle that you created.

Bundle skuDetails = mService.getSkuDetails(3, 
   getPackageName(), "inapp", querySkus);

If the request is successful, the returned Bundlehas a response code of BILLING_RESPONSE_RESULT_OK (0).

Warning: Do not call the getSkuDetails method on the main thread. Calling this method triggers a network request which could block your main thread. Instead, create a separate thread and call the getSkuDetails method from inside that thread.

To see all the possible response codes from Google Play, see In-app Billing Reference.

The query results are stored in a String ArrayList with key DETAILS_LIST. The purchase information is stored in the String in JSON format. To see the types of product detail information that are returned, see In-app Billing Reference.

In this example, you are retrieving the prices for your in-app items from the skuDetails Bundle returned from the previous code snippet.

int response = skuDetails.getInt("RESPONSE_CODE");
if (response == 0) {
   ArrayList<String> responseList
      = skuDetails.getStringArrayList("DETAILS_LIST");
   
   for (String thisResponse : responseList) {
      JSONObject object = new JSONObject(thisResponse);
      String sku = object.getString("productId");
      String price = object.getString("price");
      if (sku.equals("premiumUpgrade")) mPremiumUpgradePrice = price;
      else if (sku.equals("gas")) mGasPrice = price;
   }
}

Purchasing an Item

To start a purchase request from your app, call the getBuyIntent method on the In-app Billing service. Pass in to the method the In-app Billing API version (“3”), the package name of your calling app, the product ID for the item to purchase, the purchase type (“inapp” or "subs"), and a developerPayload String. The developerPayload String is used to specify any additional arguments that you want Google Play to send back along with the purchase information.

Bundle buyIntentBundle = mService.getBuyIntent(3, getPackageName(),
   sku, "inapp", "bGoa+V7g/yqDXvKRqq+JTFn4uQZbPiQJo4pf9RzJ");

If the request is successful, the returned Bundle has a response code of BILLING_RESPONSE_RESULT_OK (0) and a PendingIntent that you can use to start the purchase flow. To see all the possible response codes from Google Play, see In-app Billing Reference. Next, extract a PendingIntent from the response Bundle with key BUY_INTENT.

PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");

To complete the purchase transaction, call the startIntentSenderForResult method and use the PendingIntent that you created. In this example, you are using an arbitrary value of 1001 for the request code.

startIntentSenderForResult(pendingIntent.getIntentSender(),
   1001, new Intent(), Integer.valueOf(0), Integer.valueOf(0),
   Integer.valueOf(0));

Google Play sends a response to your PendingIntent to the onActivityResult method of your application. The onActivityResult method will have a result code of Activity.RESULT_OK (1) or Activity.RESULT_CANCELED (0). To see the types of order information that is returned in the response Intent, see In-app Billing Reference.

The purchase data for the order is a String in JSON format that is mapped to the INAPP_PURCHASE_DATA key in the response Intent, for example:

'{ 
   "orderId":"12999763169054705758.1371079406387615", 
   "packageName":"com.example.app",
   "productId":"exampleSku",
   "purchaseTime":1345678900000,
   "purchaseState":0,
   "developerPayload":"bGoa+V7g/yqDXvKRqq+JTFn4uQZbPiQJo4pf9RzJ",
   "purchaseToken":"opaque-token-up-to-1000-characters"
 }'

Note: Google Play generates a token for the purchase. This token is an opaque character sequence that may be up to 1,000 characters long. Pass this entire token to other methods, such as when you consume the purchase, as described in Consume a Purchase. Do not abbreviate or truncate this token; you must save and return the entire token.

Continuing from the previous example, you get the response code, purchase data, and signature from the response Intent.

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {	
   if (requestCode == 1001) {    	
      int responseCode = data.getIntExtra("RESPONSE_CODE", 0);
      String purchaseData = data.getStringExtra("INAPP_PURCHASE_DATA");
      String dataSignature = data.getStringExtra("INAPP_DATA_SIGNATURE");
        
      if (resultCode == RESULT_OK) {
         try {
            JSONObject jo = new JSONObject(purchaseData);
            String sku = jo.getString("productId");
            alert("You have bought the " + sku + ". Excellent choice, 
               adventurer!");
          }
          catch (JSONException e) {
             alert("Failed to parse purchase data.");
             e.printStackTrace();
          }
      }
   }
}

Security Recommendation: When you send a purchase request, create a String token that uniquely identifies this purchase request and include this token in the developerPayload.You can use a randomly generated string as the token. When you receive the purchase response from Google Play, make sure to check the returned data signature, the orderId, and the developerPayload String. For added security, you should perform the checking on your own secure server. Make sure to verify that the orderId is a unique value that you have not previously processed, and the developerPayload String matches the token that you sent previously with the purchase request.

Querying for Purchased Items

To retrieve information about purchases made by a user from your app, call the getPurchases method on the In-app Billing Version 3 service. Pass in to the method the In-app Billing API version (“3”), the package name of your calling app, and the purchase type (“inapp” or "subs").

Bundle ownedItems = mService.getPurchases(3, getPackageName(), "inapp", null);

The Google Play service returns only the purchases made by the user account that is currently logged in to the device. If the request is successful, the returned Bundle has a response code of 0. The response Bundle also contains a list of the product IDs, a list of the order details for each purchase, and the signatures for each purchase.

To improve performance, the In-app Billing service returns only up to 700 products that are owned by the user when getPurchase is first called. If the user owns a large number of products, Google Play includes a String token mapped to the key INAPP_CONTINUATION_TOKEN in the response Bundle to indicate that more products can be retrieved. Your application can then make a subsequent getPurchases call, and pass in this token as an argument. Google Play continues to return a continuation token in the response Bundle until all products that are owned by the user has been sent to your app.

For more information about the data returned by getPurchases, see In-app Billing Reference. The following example shows how you can retrieve this data from the response.

int response = ownedItems.getInt("RESPONSE_CODE");
if (response == 0) {
   ArrayList<String> ownedSkus =
      ownedItems.getStringArrayList("INAPP_PURCHASE_ITEM_LIST");
   ArrayList<String>  purchaseDataList =
      ownedItems.getStringArrayList("INAPP_PURCHASE_DATA_LIST");
   ArrayList<String>  signatureList =
      ownedItems.getStringArrayList("INAPP_DATA_SIGNATURE");
   String continuationToken = 
      ownedItems.getString("INAPP_CONTINUATION_TOKEN");
   
   for (int i = 0; i < purchaseDataList.size(); ++i) {
      String purchaseData = purchaseDataList.get(i);
      String signature = signatureList.get(i);
      String sku = ownedSkus.get(i);
  
      // do something with this purchase information
      // e.g. display the updated list of products owned by user
   } 

   // if continuationToken != null, call getPurchases again 
   // and pass in the token to retrieve more items
}

Consuming a Purchase

You can use the In-app Billing Version 3 API to track the ownership of purchased in-app products in Google Play. Once an in-app product is purchased, it is considered to be "owned" and cannot be purchased from Google Play. You must send a consumption request for the in-app product before Google Play makes it available for purchase again.

Important: Managed in-app products are consumable, but subscriptions are not.

How you use the consumption mechanism in your app is up to you. Typically, you would implement consumption for in-app products with temporary benefits that users may want to purchase multiple times (for example, in-game currency or equipment). You would typically not want to implement consumption for in-app products that are purchased once and provide a permanent effect (for example, a premium upgrade).

To record a purchase consumption, send the consumePurchase method to the In-app Billing service and pass in the purchaseToken String value that identifies the purchase to be removed. The purchaseToken is part of the data returned in the INAPP_PURCHASE_DATA String by the Google Play service following a successful purchase request. In this example, you are recording the consumption of a product that is identified with the purchaseToken in the token variable.

int response = mService.consumePurchase(3, getPackageName(), token);

Warning: Do not call the consumePurchase method on the main thread. Calling this method triggers a network request which could block your main thread. Instead, create a separate thread and call the consumePurchase method from inside that thread.

It's your responsibility to control and track how the in-app product is provisioned to the user. For example, if the user purchased in-game currency, you should update the player's inventory with the amount of currency purchased.

Security Recommendation: You must send a consumption request before provisioning the benefit of the consumable in-app purchase to the user. Make sure that you have received a successful consumption response from Google Play before you provision the item.

Implementing Subscriptions

Launching a purchase flow for a subscription is similar to launching the purchase flow for a product, with the exception that the product type must be set to "subs". The purchase result is delivered to your Activity's onActivityResult method, exactly as in the case of in-app products.

Bundle bundle = mService.getBuyIntent(3, "com.example.myapp",
   MY_SKU, "subs", developerPayload);

PendingIntent pendingIntent = bundle.getParcelable(RESPONSE_BUY_INTENT);
if (bundle.getInt(RESPONSE_CODE) == BILLING_RESPONSE_RESULT_OK) {
   // Start purchase flow (this brings up the Google Play UI).
   // Result will be delivered through onActivityResult().
   startIntentSenderForResult(pendingIntent, RC_BUY, new Intent(),
       Integer.valueOf(0), Integer.valueOf(0), Integer.valueOf(0));
}

To query for active subscriptions, use the getPurchases method, again with the product type parameter set to "subs".

Bundle activeSubs = mService.getPurchases(3, "com.example.myapp",
                   "subs", continueToken);

The call returns a Bundle with all the active subscriptions owned by the user. Once a subscription expires without renewal, it will no longer appear in the returned Bundle.

Securing Your Application

To help ensure the integrity of the transaction information that is sent to your application, Google Play signs the JSON string that contains the response data for a purchase order. Google Play uses the private key that is associated with your application in the Developer Console to create this signature. The Developer Console generates an RSA key pair for each application.

Note:To find the public key portion of this key pair, open your application's details in the Developer Console, then click on Services & APIs, and look at the field titled Your License Key for This Application.

The Base64-encoded RSA public key generated by Google Play is in binary encoded, X.509 subjectPublicKeyInfo DER SEQUENCE format. It is the same public key that is used with Google Play licensing.

When your application receives this signed response you can use the public key portion of your RSA key pair to verify the signature. By performing signature verification you can detect responses that have been tampered with or that have been spoofed. You can perform this signature verification step in your application; however, if your application connects to a secure remote server then we recommend that you perform the signature verification on that server.

For more information about best practices for security and design, see Security and Design.