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Android OS : Core Concepts Dr. Jeyakesavan Veerasamy Sr. Lecturer University of Texas at Dallas

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1 Android OS : Core Concepts Dr. Jeyakesavan Veerasamy Sr. Lecturer University of Texas at Dallas

2 Agenda Introduction to Android devices Environment overview Android concepts Application components – Activities, Services, Content providers, Broadcast receivers “Hello” application Summary

3 Development Environment Java Development Kit (JDK) Eclipse IDE Android Development Tools (ADT) plug-in SDK starter package – Platforms (1.0, 2.0, 3.0, 4.1, …) – Tools (debug, …) Reference: JDK Eclipse ADT Plug-in Android SDK

4 Development Process for Android Applications

5 Android Architecture

6 Android Runtime Environment Dalvik VM for each application common Linux kernel JRE x.classy.class Linux kernel VM APP …

7 Basics: UNIX security compare it with Windows security

8 Application Security Android operating system is based on multi- user Linux system. Each application is treated as a different user. Each application uses unique Linux user ID. Every application runs as a Linux process.

9 Application security … It's possible to arrange for two applications to share the same Linux user ID, in which case they are able to access each other's files – can run as same Linux process and share the same VM (applications use same certificate). An application can request permission to access device data such as the user's contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. All application permissions must be granted by the user at install time.

10 Processes & Threads Every application runs in its own process and all components of the application run in that process, by default -- UI thread Any slow, blocking operations in an activity should be done in a new thread, to avoid slowing down the user interface. – If application does not respond in 5 seconds, "application not responding" (ANR) dialog appears.application not responding

11 Process lifecycle: Importance Hierarchy Foreground process Visible process Service process Background process Empty process “Lower importance” tasks may be killed by Android – why? How to select a lucky one from a pool?

12 IPC Remote procedure calls (RPCs)

13 Android Application components Activities - front-end UI screens Services – back-end support Content providers – application data – SQLite, web or SD card Broadcast receivers – handle system events

14 Activitating Components: Intent

15 Basics: Data Exchange A1 A3 A2 A4

16 Basics: Data Exchange Binary or text data  XML or JSON … Independent data checkers tools available. A1 A3 A2 A4

17 Sample XML data file Text format: Belgian Waffles, 5.95, two of our famous Belgian Waffles with plenty of real …, 650 Strawberry Belgian Waffles, 7.95, light Belgian waffles covered with …., 900

18 Application info: Manifest file Declare components Declare application requirements Application Resources?

19 Activity lifecycle: 3 states Resumed or Running Paused Stopped

20 State machine

21 Code

22 Service Lifecycle

23 User Interface Design

24 XML Layouts Declare UI elements in XML. Android provides a straightforward XML vocabulary that corresponds to the View classes and subclasses. Instantiate layout elements at runtime. Your application can create View and ViewGroup objects (and manipulate their properties) programmatically.

25 Application Resources

26 Building & running Android app

27 Program to say “Hello!”

28 Native Development Kit (NDK) Use C/C++ for development primarily for performance critical components

29 Summary Clean, sophsticated, yet reasonably simple. Android requires strong Java skills – heavy use of derived classes (inheritance). Development: Java code & XML definitions Reference: Install Android development environment and play with a few examples or try your own ideas! Marketable skill in the industry!

30 More references mple mple

31 Questions & Answers

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