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

Apache Cordova is a platform for building native mobile applications using HTML, CSS and JavaScript.

The plugin provides access to the standard interface that manages the editing and sending an email message. You can use this view controller to display a standard email view inside your application and populate the fields of that view with initial values, such as the subject, email recipients, body text, and attachments. The user can edit the initial contents you specify and choose to send the email or cancel the operation. Using this interface does not guarantee immediate delivery of the corresponding email message. The user may cancel the creation of the message, and if the user does choose to send the message, the message is only queued in the Mail application outbox. This allows you to generate emails even in situations where the user does not have network access, such as in airplane mode. This interface does not provide a way for you to verify whether emails were actually sent. Using this interface does not guarantee immediate delivery of the corresponding email message. The user may cancel the creation of the message, and if the user does choose to send the message, the message is only queued in the Mail application outbox. This allows you to generate emails even in situations where the user does not have network access, such as in airplane mode. This interface does not provide a way for you to verify whether emails were actually sent.

Ionic makes it incredibly easy to build beautiful and interactive mobile apps using HTML5 and AngularJS. An open source mobile UI toolkit for building high quality, cross-platform native and web app experiences. Move faster with a single code base, running everywhere with JavaScript and the Web.

Okio is a new library that complements java.io and java.nio to make it much easier to access, store, and process your data.A modern I/O library for Android, Kotlin, and Java

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.