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Trivial Drive Kotlin

Sample for In-App Billing version 3


This sample is provided to demonstrate Google Play In-app Billing for very large (or very small) apps. To read more visit

This game is a simple "driving" game where the player can buy gas and drive. The car has a tank which stores gas. When the player purchases gas, the tank fills up (1/4 tank at a time). When the player drives, the gas in the tank diminishes (also 1/4 tank at a time).

The user can also purchase a "premium upgrade" that gives them a red car instead of the standard blue one (exciting!).

The user can also purchase a subscription ("gold status") that allows them to drive with a gold car background while that subscription is active. The subscription can either be purchased monthly or yearly.



Screenshot1 Screenshot2

Getting Started

This sample can be run as-is. However, you are encouraged to create your own application instance in the Developer Console and modify this sample to point to it. Here is what you should do:


  1. Create an application on the Developer Console, available at

  2. Copy the application's public key (a base-64 string). You can find this in the "Services & APIs" section under "Licensing & In-App Billing".


  1. Open Security.kt, find the declaration of BASE_64_ENCODED_PUBLIC_KEY constant and replace its value with the public key you retrieved in Step 2.

  2. Change the sample's package name to your package name. You can update the package name by setting the APP_ID in the root project build.gradle file.

  3. Update with your release keystore information.

    The storeFile location can be a relative or absolute filename.

    Or, you can sign your APK from Android Studio "Build -> Generate Signed APK..."


  1. Upload your APK to Google Play for Alpha Testing.

  2. Make sure to add your test account (the one you will use to test purchases) to the "testers" section of your app. Your test account CANNOT BE THE SAME AS THE PUBLISHER ACCOUNT. If it is, your purchases won't go through.

  3. Under In-app Products, create MANAGED in-app items with these IDs: "premium_car" and "gas". Fill in their prices and other fields. Set them to "Active".

  4. Under In-app Products, create SUBSCRIPTION items with these IDs: "gold_monthly" and "gold_yearly". Fill their prices and other fields. Set them to "Active".

  5. Publish your APK to the Alpha channel. Wait 2-3 hours for Google Play to process the APK. If you don't wait for Google Play to process the APK, you might see errors where Google Play says that "this version of the application is not enabled for in-app billing" or something similar.

  6. Also always make sure that the uploaded application has the same version as the one you are testing.


  1. Install the APK signed with your PRODUCTION certificate, to a test device [*].
  2. Run the app.
  3. Make purchases using the test account you added in Step 7.

If you don't want your credit card to be charged, you can include your test account inside the list of "testing access". To know more about this, please read the section "Setting up test purchases" inside the following guide:

Otherwise, you can refund any real purchases you make, to avoid the charges.

[*]: it will be easier to use a test device that doesn't have your developer account logged in; this is because, if you attempt to purchase an in-app item using the same account that you used to publish the app, the purchase will not go through.


This sample app implements signature verification but does not demonstrate how to enforce a tight security model. When releasing a production application to the general public, we highly recommend that you implement the security best practices described in our documentation at:

In particular, you should perform a security check on your backend.


If you've found an error in this sample, please file an issue:

Patches are encouraged, and may be submitted by forking this project and submitting a pull request through GitHub.


Copyright 2018 Google, Inc.

Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


2018-12-26: Initial release

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