Chapter 02. Android App Fundamentals

Android App Fundamentals

Overview

Android Architecture

• Runs on top of Linux 2.6
• Dalvik virtual machine optimized for mobile devices
• Integrated browser based on WebKit engine
• Optimized Graphics with OpenGL ES
• SQLite database for structured data Storage

Android Versions

Application Fundamentals

• Applications are written in the Java programming language
• Compiled into and Android package (.apk)
• Each application runs on its own sandbox and Linux process
• Applications consists of components, a manifest file
• and resources

Components:

• Activities
• Services
• Concept Providers
• Broadcast Receivers

Activities

• An activity represents a single screen with user interface
• Most applications have multiple activities
• When a new activity starts, it is pushed onto the back stack
• User interface can be built on XML or in Java
• Monitor lifespan through callback methods like onStart(), onPause(), etc

Services

• Services perform long-running operations in the background
• Does not contain a user interface
• Useful for things like network operations, playing music, etc
• Runs independently of the component that created it
• Can be bound to by other applications, if allowed

Content Providers

• Used to store and retrieve data and make it accessible to all applications
• Are the only way to share data across applications
• Exposes a public URI that uniquely identifies its data set
• Data is exposed as simple table on a database model
• Android Contains many providers for this like contacts, media, etc

Broadcast Receivers

• A component that responds to system-wide broadcast announcements
• Examples include when the screen is off, the battery is low, etc
• Applications can also initiate their own broadcasts
• Broadcast receivers contain no user interface
• They can create status bar notifications to alert the user

Android Manifest file

• Applications must have an AndroidManifest.xml file in its roots directory
• Presents information about the application to the Android system
• Describes the components used in the application
• Declares the permissions required to run the application
• Declares the minimum Android API level that the application requires

Project Structure

• Project Name
• Select Android minimum API level
• Application Name
• Package Name
• Create Activity

Application Manifest

• Manifest
• Application
• Permissions
• Instrumentation
• AndroidManifest.xml File

Activities

Explicit Intents

Implicit Intents

Resources

Permission

Debugging