Android Architecture

• Android runs on the top of Linux Operating System.
• It has Dalvik Virtual Machine (DVM), optimized for mobile phones.
• It is integrated browser based on Web kit engine.
• Open GL ES for graphics.
• Sqlite Support for database.
• Media Support
• GSM Technology
• Bluetooth, EDGE, 3G, wi-fi

Application Fundamentals

• It is mostly written in java programming language.
• Final output of the android program is .apk file.
• Android consist of Components, resources, and AndroidManifest file.
• Components of Android are:-

1. Activities
2. Services
3. Content Providers
4. Broadcast Receiver

Activites

• An Activity represents User Interface which is visible to the user.
• Typically an android application have many activities.
• Every Activity in android has a life Cycle.
• User Interface can be built in XML or Java.

Services

• Service performs long running operation in the background.
• Service doesn't have any User Interface.
• Example:- music player is the example of service.

Content Providers

• Content Providers is the interface to data for all the application.
• Can be used to store and retrieve data and make it accessible to all application.
• Example:- Content Providers for the Contacts, if we want to access phonebook through any application.

Broadcast Receiver

• It is the component that will respond to the system wide events.
• It doesn’t have any User Interface.
• An application can have its own Broadcast Receiver that will respond to the particular event.
• Example :- Incoming call is an events, that Broadcast Receiver will receive and you can perform some action when any incoming call comes.

Android Manifest file

• It is in the root of the android project folder.
• It describes used components in the application.
• It describes the permission need to run the application.