ANDROID

1. What is Android?

1.1. The Android operating system

1.2. Task

1.3. Android platform components

1.4. Google Play

1. What is Android?

1.1. The Android operating system

Android is an operating system based on the Linux kernel. The project responsible for developing the Android system is called the Android Open Source Project (AOSP) and is primarily lead by Google.

The Android system supports background processing, provides a rich user interface library, supports 2-D and 3-D graphics using the OpenGL-ES (short OpenGL) standard and grants access to the file system as well as an embedded SQLite database.

An Android application typically consists of different visual and non visual components and can reuse components of other applications.

1.2. Task

In Android the reuse of other application components is a concept known as task. An application can access other Android components to achieve a task. For example, from a component of your application you can trigger another component in the Android system, which manages photos, even if this component is not part of your application. In this component you select a photo and return to your application to use the selected photo.

Such a flow of events is depicted in the following graphic.

1.3. Android platform components

The Android system is a full software stack, which is typically divided into the four areas as depicted in the following graphic.

The levels can be described as: 

• Applications - The Android Open Source Project contains several default application, like the Browser, Camera, Gallery, Music, Phone and more.
• Application framework - An API which allows high-level interactions with the Android system from Android applications.
• Libraries and runtime - The libraries for many common functions (e.g.: graphic rendering, data storage, web browsing, etc.) of the Application Framework and the Dalvik runtime, as well as the core Java libraries for running Android applications.
• Linux kernel - Communication layer for the underlying hardware.

The Linux kernel, the libraries and the runtime are encapsulated by the application framework. The Android application developer typically works with the two layers on top to create new Android applications.

1.4. Google Play

Google offers the Google Play service, a marketplace in which programmers can offer their Android applications to Android users. Customers use theGoogle Play application which allows them to buy and install applications from the Google Play service.

Google Play also offers an update service. If a programmer uploads a new version of his application to Google Play, this service notifies existing users that an update is available and allows them to install the update.

Google Play provides access to services and libraries for Android application programmers, too. 

For example, it provides a service to use and display Google Maps and another to synchronize the application state between different Android installations. Providing these services via Google Play has the advantage that they are available for older Android releases and can be updated by Google without the need for an update of the Android release on the phone.