Make and receive phone calls in Android apps with Firebase

With Nexmo In-App Voice, developers can easily make and receive phone calls directly within their Android app using the Nexmo Stitch Android SDK and WebRTC technology. The functionality allows customers to make outbound calls without leaving the app, and receive incoming calls from other users. To get started, developers need a Vonage API account, set up Firebase Functions to host the NCCO and return a JWT for users to login with, deploy the Firebase project, create a Vonage application, link a phone number and user to the app, and set up the Android project using Retrofit. The Nexmo Stitch SDK handles the hard work of placing and answering phone calls, allowing developers to focus on building their app's UI and logic.