What an Android magic box has inside?

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Okay, its time to understand the internals of Android OS and folder structure of Android application.

When we write a desktop application, we are the masters of using the controls which range from simple textbox to dialog box. Desktop app usually has main window – Window and child window controls – Textbox, Label etc., We use database to store and retrieve information by using JDBC, ODBC technologies to establish communication between application and DB.

Android also has similar concepts, but built differently, and structured to make phones more crash-resistant. They are:

• Activity
• Content Providers
• Intents
• Services

The building block of the user interface is the activity. You can think of an activity as being the Android analogue clock for the android window or dialog in a traditional desktop application. Every android application should have at-least one activity if the application involves UI. Every class must inherit Activity class which is the predefined class in android.app.Activity package provided by Google. It is possible for activities to not have a user interface, most likely they will be content providers or services which are described here.

Stuffs involved in Android

LeftRight

Storage

You can package data files with your application, for now that do not change, such as icons or help files. You also can carve out a small bit of space on the device itself, for databases or files containing user-entered or retrieved data needed by your application. And, if the user supplies bulk storage, like an SD card, you can read and write files on there as needed. To be more specific, Android provides in built database – SqlLite

As of now, we discussed about the contents involved in Android OS. Let us shed some light on Project structure and folders in Android application:

• AndroidManifest.xml
• build.xml
• bin/
• src/
• res/

An XML file which describes the application. The foundation for any Android application is the manifest file: AndroidManifest.xml in the root of your project. Here is where you declare what all is inside your application – the activities, the services, and so on.

Resources folder has many folders inside it, they are:

• res/drawable/
• res/layout/
• res/raw/
• res/values/

Holds images (PNG, JPEG, etc.)