Basic Building Blocks Of Android:
(1) Activities: These are our Application's presentation layer. Every screen in our application is a subclass of Activity. Activities use views to create user interface
(2) Services:These run in background updating data and resources required for an activity and triggering through notifications. They perform normal processing that needs to be done even when activity is invisible.
(3)Intents:These are the messages sent across system wide targeting an activity or service to be launched specifying their intention to have some action performed.These are simple messaging passing framework.
(4)Broadcast Receivers: By creating and registering broadcast receivers , your applications are free to listen broadcast intents upon matching specific criteria will launch activity automatically.These are called Intent consumers.
(5)Content Providers:Content Providers are the best way to share data across applications.By creating content providers we can expose the data of your application to be accessed by other applications . And also we can use default content providers like Contacts to access contacts details.
(6)Notifications: Notifications are used to notify users with out stealing the focus of the currently running applications. Examples include sms,call,alarm,flash back light.
