Use Play Billing in your Trusted Web Activity

André Cipriani Bandarra

Besides allowing your app to sell digital goods and subscriptions on the Play Store, Google Play Billing offers tools for managing your catalog, prices and subscriptions, useful reports, and a checkout flow powered by the Play Store that is already familiar to your users. It is also a requirement for applications published on the Play Store that sell digital goods.

Chrome 88 is launching with an Origin Trial on Android that enables the integration of Trusted Web Activities with the Payment Request API and the Digital Goods API to implement purchase flows via Google Play Billing. We expect this Origin Trial to also be available for ChromeOS on version 89.

In order to ease the integration to the Android app, the Trusted Web Activity team is introducing an extension library to android-browser-helper. This guide will show you the changes required to integrate this library into an existing application.

Note: This articles covers the integration for the Android app. If you are using Bubblewrap to build your application you will be able to use the tool to update your app. The implementation on Bubblewrap is being tracked in this issue. This guide is meant for those who are not using Bubblewrap to update their app.

build.gradle

The billing extension library itself depends on version 2.1.0 of android-browser-helper. Ensure your application is using a version that is equal or greater than that.

You will also need to add an implementation declaration for the billing extension library:

dependencies {
    ...
    implementation 'com.google.androidbrowserhelper:androidbrowserhelper:2.1.0'
    implementation 'com.google.androidbrowserhelper:billing:1.0.0-alpha05'
}

DelegationService.java

android-browser-helper ships with a default DelegationService that can be used directly by apps. When using the billing extension, you need a slightly customized version of the DelegationService.

In order to do that, you will need to create your own DelegationService class that extends the original one and overrides onCreate(). Inside onCreate(), you will need to add a single method call that registers the application as a handler for the Digital Goods API:

package com.example.yourapp;

import com.google.androidbrowserhelper.playbilling.digitalgoods.DigitalGoodsRequestHandler;
import com.google.androidbrowserhelper.trusted.DelegationService;

public class DelegationService
        extends com.google.androidbrowserhelper.trusted.DelegationService {
    @Override
    public void onCreate() {
        super.onCreate();
        registerExtraCommandHandler(new DigitalGoodsRequestHandler(getApplicationContext()));
    }
}

AndroidManifest.xml

On the Android Manifest, you will need to change the reference to the Delegation Library your own implementation. In the corresponding service declaration, replace com.google.androidbrowserhelper.trusted.DelegationService with your newly created class.

<service
    android:name=".DelegationService"
    android:exported="true">

    <intent-filter>
        <action android:name="android.support.customtabs.trusted.TRUSTED_WEB_ACTIVITY_SERVICE"/>
        <category android:name="android.intent.category.DEFAULT"/>
    </intent-filter>
</service>

The billing library also introduces two new components that will need to be added to your Android Manifest: a Service that the browser can connect to and check if the application supports the payment, and an Activity that handles the payment flow itself:

<activity
    android:name="com.google.androidbrowserhelper.playbilling.provider.PaymentActivity"
    android:theme="@android:style/Theme.Translucent.NoTitleBar"
    android:configChanges="keyboardHidden|keyboard|orientation|screenLayout|screenSize"
    android:exported="true">
    <intent-filter>
        <action android:name="org.chromium.intent.action.PAY" />
    </intent-filter>
    <meta-data
        android:name="org.chromium.default_payment_method_name"
        android:value="https://play.google.com/billing" />
</activity>
<!-- This service checks who calls it at runtime. -->
<service
    android:name="com.google.androidbrowserhelper.playbilling.provider.PaymentService"
    android:exported="true" >
    <intent-filter>
        <action android:name="org.chromium.intent.action.IS_READY_TO_PAY" />
    </intent-filter>
</service>

Learn more about the Digital Goods API and Google Play Billing

This article covered the steps needed specifically on the Android application that uses Trusted Web Activity, but the Google Play Billing API has its own terminology and includes client and backend components. We strongly recommend reading the Google Play Billing and the Digital Goods API documentation and understanding its concepts before integrating it into an application in production.