Key elements in Android Application
Key elements in Android Application are activities, views, intents, content providers, services, and the AndroidManifest.xml file.
View – are building blocks of a user interface, and they know how to draw themselves. This concept carries over to Android from J2EE and Swing.
Activity – usually represents as single screen in Android application. In general it contains one or more views, but there are viewless activity such as “Service”.
Intent – defines an “intention” to do some work. Developer can use intents to perform tasks, as broadcast a message, start a service, launch an activity or display a web page. Intents also could be used by the system to notify application of specific events (such as the arrival of a text message). Intents are loosely couple the action and action handler.
Content Provider – defines a standard mechanism for applications to share data (such as a list of contacts) without exposing the underlying storage, structure, and implementation.
Services – background processes that can potentially run for a long time. Android defines two types of services: local services (accessible by the application that is hosting the service) and remote services (that are meant to be accessed remotely by other applications running on the device). Developer can use existing services and write own services by extending the Service class.
AndroidManifest.xml – defines the contents and behavior of application, it lists application activities and services, along with the permissions.