• Each application runs it’s own process

• Each process has its own separate virtual machine

• Each application is assigned a unique linux user -ID

Application Fundamentals

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Application Fundamentals Types

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Activity

Intent

Android Manifest

Content Provider

Service

Broadcast Receiver

Activity

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Basic component of most applications

Most applications have more than one activities that all start each other as needed

Each activity implements as a subclass of base Activity class.

Each activity is default window

The content of window is view or group of views

Example of views : text , buttons , scroll bars ,menu items etc…

Activity represents presentation layer in android UI.

Intents

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An Intent is exactly what it describes. It's an "intention" to do an action.

An Intent is a messaging object you can use to request an action from anotherapp component.

An Intent is basically a message to say you did or want something to happen.

Although intents facilitate communication between components in several ways.

Types of Intents

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•Specify the component to start by name because you know the class name of the activity or service you want to start,For example, start a new activity in response to a user action or start a service to download a file in the background

Explicit intents

•Do not name a specific component but instead declare a general action to perform which allows a component from another app to handle it. For example, if you want to show the user a location on a map, you can use an implicit intent to request that another capable app show a specified location

Implicit intents

Android Manifest

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<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.helloworld"android:versionCode="1" android:versionName="1.0" >

<uses-sdkandroid:minSdkVersion="8"android:targetSdkVersion="15" />

<application android:icon="@drawable/ic_launcher"android:label="@string/app_name"android:theme="@style/AppTheme" ><activity

android:name=".MainActivity"android:label="@string/title_activity_main" ><intent-filter>

<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" /></intent-filter>

</activity></application>

</manifest>

Elements of Android Manifest File

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•root element of the AndroidManifest.xml file

•It includes the namespace declaration

•It has package attribute that describes the package name of the activity class<manifest>

•contains several sub elements

•The commonly used attributes are of this element are icon, label, theme etc.<application>

•Each activity must be defined

•android:label represents a label for the activity, often displayed on the screen

•android:name represents a name for the activity class. It is required attribute<activity>

•describes the type of intent to which activity, service or broadcast receiver<intent-filter>

•It adds an action for the intent-filter

•intent-filter must have one or more action elements<action>

•It adds an category name to an intent-filter<category>

Content Providers

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Supplies data from one application to others on request

Such requests are handled by the methods of the ContentResolver class

A content provider can use different ways to store its data and the data can be stored in a database, in files, or even over a network

Service

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❏ Does not have visual interface❏ Runs in background indefinitely❏ Examples:

Playing Music

❏ You can bind to a an existing service and control its operation

❏ Content provider and intents are short lived but services are always running

❏ Suppose even you exit from app ,the background process running.

Broadcast Receiver

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Receive and react to

broadcast announcements

Extend the class BroadcastReceiver

Examples:

•Low battery, power connected, shutdown, time zone changed, etc.

A broadcast receiver is an Android component which allows you to register for system or application events.