The Android platform provides a framework API that applications can use to interact with the underlying Android system. The framework API consists of: A core set of packages and classes. A set of permissions that applications can request, as well as permission enforcements included in the system

The Google Analytics SDK for Android makes it easy for native Android developers to collect user engagement data from their applications. Developers can then use the Google Analytics reports to measure: The number of active users are using their applications. From where in the world the application is being used. Adoption and usage of specific features. Crashes and exceptions. In-app purchases and transactions. And many other useful metrics... The Google Analytics SDK also gives you the tools to monitor the success of mobile marketing campaigns. Connect user interactions with paid ads, Google Play downloads, and subsequent in-app usage and Ecommerce transactions. Google Analytics provides a powerful platform to measure and optimize all of your application marketing efforts.

Deprecated Google Cloud Messaging for Android (GCM) is a service that allows you to send data from your server to your users' Android-powered device, and also to receive messages from devices on the same connection. The GCM service handles all aspects of queueing of messages and delivery to the target Android application running on the target device. GCM is completely free no matter how big your messaging needs are, and there are no quotas.

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

Make your games social with Google Play game services. Add achievements, leaderboards, real-time multiplayer, and other popular features using the Google Play game services SDK. Let players sign in using their Google+ identities and share their gaming experience with friends. Visit developers.google.com/games/services for more information about integrating game services into your app.

Google Play services powers a broad set of SDKs on Android to help you build your app, enhance privacy and security, engage users, and grow your business. These SDKs are unique in that they only require a thin client library to be included in your app, as shown in figure 1. At runtime, the client library communicates with the bulk of the SDK's implementation and footprint in Google Play services.

Google Sign-In is a secure authentication system that reduces the burden of login for your users, by enabling them to sign in with their Google Account—the same account they already use with Gmail, Play, Google+, and other Google services. Google Sign-In is also your gateway to connecting with Google’s users and services in a secure manner. You can give your users the opportunity to pay with Google Pay, share with their Google-wide contacts, save a file to Drive, add an event to Calendar, and more. Integrate Google’s user-centric APIs and services inside your app to help your users take action and convert.

Square helps millions of sellers run their business-from secure credit card processing to point of sale solutions. Get paid faster with Square.

HTTP is the way modern applications network. It’s how we exchange data & media. Doing HTTP efficiently makes your stuff load faster and saves bandwidth. OkHttp is an HTTP client that’s efficient by default: HTTP/2 support allows all requests to the same host to share a socket. Connection pooling reduces request latency (if HTTP/2 isn’t available). Transparent GZIP shrinks download sizes. Response caching avoids the network completely for repeat requests. OkHttp perseveres when the network is troublesome: it will silently recover from common connection problems. If your service has multiple IP addresses OkHttp will attempt alternate addresses if the first connect fails. This is necessary for IPv4+IPv6 and for services hosted in redundant data centers. OkHttp supports modern TLS features (TLS 1.3, ALPN, certificate pinning). It can be configured to fall back for broad connectivity. Using OkHttp is easy. Its request/response API is designed with fluent builders and immutability. It supports both synchronous blocking calls and async calls with callbacks.

Paging indicator widgets compatible with the ViewPager from the Android Support Library and ActionBarSherlock.Paging indicator widgets that are compatible with the ViewPager from the Android Support Library to improve discoverability of content.