After you've finished developing your app, you're ready to reap the financial benefits of your work. In this course, learn about the Google Play In-app Billing API, and how to use it effectively to sell digital products within your app. Instructor Albert Lo kicks off the course by explaining how to set up your existing app for in-app purchases by modifying the UI. Next, he acquaints you with the Gradle build system, and shows how to leverage it to support in-app purchases. Albert then provides an overview of the billing process, and shows how to define your digital products, and use the Google in-app library to query purchased items, launch the purchase flow from both one-time purchases and subscriptions, and handle responses.