CS 423 – Operating Systems Design

Lecture 24 – Google Android System Klara Nahrstedt Fall 2011 Based on slides from Andrew S. Tanenbaum textbook and other web-material (see acknowledgements)

cs423 Fall 2011

1

Overview Administrative

◦ MP3 going on ◦ Pickup Midterms and HWs ◦ Reboot your VM if you have not done so Android

History Android Architecture Selected Important and New Concepts

cs423 Fall 2011

2

What is Android? Google

 OHA (Open Handset Alliance)

◦ The first truly open and comprehensive platform for mobile devices, all of the software to run a mobile phone but without the proprietary obstacles that have hindered mobile innovation. ◦ Linux OS kernel ◦ Java programming ◦ Open source libraries: SQLite, WebKit, OpenGL

Why Android ? A

simple and powerful SDK No licensing, distribution, or development fees Development over many platform ◦ Linux, Mac OS, windows Excellent

documentation Thriving developer community

History of Android (1) Google

2005

purchases startup company Android Inc.

◦ Development of Android Platform starts

2007

– Open Handset Alliance around Android Platform

◦ Sprint, T-Mobile, Motorola, Samsung, Sony Ericsson, Toshiba, Vodafone, Google, Intel, Texas Instrument ◦ Key architectural goals of Android Platform was always openness ◦ Allow applications to interact with one another and reuse components from one another

2008

– Android Dev Phone 1 (Android OS 1.1)

◦ Applications running without being tied to any cell phone provider network !!! cs423 Fall 2011

History of Android (2) 2009

◦ April 2009 – release 1.5 Android OS with advanced media-recording, widgets, live folders ◦ September 2009 – release 1.6 Android OS with advanced search capabilities, text to speech, gesture and multi-touch

2010

◦ Android 2.0 – usage of HTML

2011

◦ Android 2.2 (Fro Yo) ◦ Android 2.3 (Gingerbread) ◦ Android 3.0 (Honeycomb) cs423 Fall 2011

Android Features Application

framework

◦ Enabling reuse and replacement of components

Dalvik

virtual machine optimized for mobile devices Integrated browser based on open source WebKit engine Optimized graphics

◦ Powered by custom 2F graphics library, 3D graphics based on OpenGL

SQLite for structured data storage Media support for audio/video/still image

formats (MPEG4, H. 264, MP3, JPG, …)

Source: http://developer.android.com/guide/basics/what-is-android.html

cs423 Fall 2011

Android Features GSM

telephony Bluetooth, EDGE, 3G, WiFi (hardware dependent) Camera, GPS, compass, accelerometer (hardware dependent) Rich development environment ◦ Including device emulator, tools for debugging, memory and performance profiling and plugin for Eclipse IDE Location-based  Manufacturer

service (map – Google API)

Independent Abstractions to Hardware

Source: http://developer.android.com/guide/basics/what-is-android.html

cs423 Fall 2011

Android Architecture

cs423 Fall 2011

Android Application Framework Open development platform Capabilities to build extremely

innovative applications Developers

rich and

◦ take advantage of device hardware, access location information, run background services, set alarms, notifications to the status bar, etc ◦ Have full access to the same framework APIs used by core apps ◦ Application architecture designed to simplify reuse of components ◦ Any app can publish its capabilities and any other app may then make use of those capabilities (subjet to security constraints) cs423 Fall 2011

Android Application Framework  Underlying

all applications is a set of services and

systems:  Rich and extensible set of views

◦ They can be used to build app including lists, grids, text boxes, buttons, even embeddable web browser

 Content

providers that enable apps to access data from other apps (such as contacts) or to share their won data  Resource manager, providing access to non-code resources such as localized strings, graphics, layout files  Notification manager that enables all apps to display custom alerts in the status bar  Activity manager that manages lifecycle of apps and provides common navigation back-stack cs423 Fall 2011

Android Application Framework Contacts

Media

Content Provider View 1 Notification Manager

Activity G U I

Service Activity Manager

Broadcast Listener Resource Provider Strings

Storage

Radio TextView Toast

View 2 Button Slider Toast

Android Runtime  Every Android

app runs its own process, with its own instance of the Dalvik virtual machine

 Dalvik

has been written so that it can run multiple VMs efficiently

 Dalvik VM

executes files in Dalvik Executable (.dex) format

D Resources E X Activity Service Dalvik VM

DEX

DEX

Dalvik VM

Dalvik VM

Linux Kernel

Android DEX ●

Optimized for minimal memory footprint ●

●

●

Global String Table

Runs classes compiled by Java language complier that have been transformed into .dex format by included “dx” tool Relies on linux kernel for threading and low-level memory management

File Header String Table Class List Field Table Method Table ... Local Variable List DEX File Format

Android Kernel Relies

on Linux version 2.6 for core services Security ◦ Leverage Linux Users and Permissions Memory

management Process management Network stack Driver model cs423 Fall 2011

Android Application Architecture Views:

◦ Building block for user interface components. Activities

◦ A single, focused thing that the user can do. ◦ Interaction with users: creating a window to place UI ◦ full-screen windows, floating windows, embedded inside of another activity ◦ Ex: Registration, Peerlist, Messaging GUI

Android Application Architecture Services

(Background)

Intent

◦ Ex: Network Communication Intent

◦ Inter-communication among activities or services Resource

◦ Externalization of strings and graphics Notification

◦ signaling users: Light, sound, icon, dialog, notification ◦ Ex: new message arrives Content

Providers

◦ share data between applications

 Layout

Java

View

of visual interface

Code

◦ Initialize

@Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.screen); }

◦ Access TextView myTextView = (TextView)findViewById(R.id.myTextView);

screen.xml

View Component

 Widget

Toolbox

◦ TextView, EditText,Button, Form, TimePicker… ◦ ListView (PeerList)

Update list by arrays ArrayAdapter myListView.setAdapter

◦ Layout

Positions of controls LinearLayout, Relativelayout ◦ http://developer.android.com/guide/tutorials/views/index.html

 Menu

◦ Exit app

Activity Foreground

invisible

Activity: suspended when

◦ Visual, interactive ◦ Ex: Game, Map

Background

Service: Little interaction

◦ Ex: Hardware, power management

User Interaction Event   

onKeyDown. onKeyUp onTrackBallEvent onTouchEvent

registerButton.setOnClickListener(new OnClickListener() { public void onClick(View arg0) {….}} myEditText.setOnKeyListener(new OnKeyListener() { public boolean onKey(View v, int keyCode, KeyEvent event) { if (event.getAction() == KeyEvent.ACTION_DOWN) if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) { … return true; } return false; }});}

User Interaction Event   

onKeyDown. onKeyUp onTrackBallEvent onTouchEvent

registerButton.setOnClickListener(new OnClickListener() { public void onClick(View arg0) {….}} myEditText.setOnKeyListener(new OnKeyListener() { public boolean onKey(View v, int keyCode, KeyEvent event) { if (event.getAction() == KeyEvent.ACTION_DOWN) if (keyCode == KeyEvent.KEYCODE_DPAD_CENTER) { … return true; } return false; }});}

Application and Component Glues An

intent is an abstract description of an operation to be performed.

Intent intent = new ◦ Launch an activity Ex: Intent(MyActivity.this, MyOtherActivity.class);

Explicit

Im: Intent intent = new Intent(Intent.ACTION_DIAL, Uri.parse(“tel:555-2368”));

Implicit: Android selects the best startActivity();

◦ Subactivity: feedback

Child: use intent as feedback, setResult Parent: onActivityResult startActivityForResult

◦ Action, data, extra parameter

intent.putExtra(name, property);

Intent Broadcast

◦ announce application events system-wide ◦ sendBroadcast ◦ MyBroadcastReceiver extends BroadcastReceiver ◦ registerReceiver (in java / in xml)

Intent

Filter

◦ Register Activities, Services, and Broadcast Receivers as being capable of performing an action on a particular kind of data.

Manifest.xml

Intent from Peerlist to Messaging

Select a peer Send Intent

PeerList

Messaging

Service 

Service class ◦ public class MyService extends Service ◦ public void onStart() {…}



Manifest.xml ◦



Control ◦ startService ◦ stopService



Communication ◦ Bind service with activity: use public method and properties ◦ Intent

Working in Background Services

◦ NO GUI, higher priority than inactive Activities ◦ Usage: responding to events, polling for data, updating Content Providers.

◦ However, all in the main thread Background

threads

Activity Lifetime

Declaration of App – Manifest.xml   

Service Activity (intent-filter) Permission ◦ Don’t forget. Otherwise, your programming won’t work

External Resources values/

◦ String, color, array, dimension, style theme drawables/

◦ Image layout/

◦ screen.xml

Tools 

The Android Emulator ◦ Implementation of the Android virtual machine ◦ Test and debug your android applications.



Dalvik Debug Monitoring Service (DDMS) ◦ Monitor and Control the Dalvik virtual machines ◦ Logcat (see logged msgs)



Android Debug Bridge (ADB) ◦ Manage the state of an emulator instance or Android-powered device ◦ Copy files, install compiled application packages, and run shell commands.



Traceview ◦ Graphical analysis tool for viewing the trace logs from your Android application ◦ Debug your application and profile its performance



MkSDCard ◦ Creates an SDCard disk image

Conclusion Important

concepts at the application framework level New concepts ◦ Activities, Broadcast Listeners, Intents ◦ Paying attention to GUI And Overall User interactions ◦ Specialized lifecycle

cs423 Fall 2011

32

Reference Online

development guide

◦ http://developer.android.com/guide/index.html

Book

resource

◦ “Professional Android Application Development”, by Reto Meier, (Wrox, amazon link) ◦ “Android A programmers guide”, by J.F. DiMarzio, (McGraw Hill, amazon link) ◦ “Beginning.Android”, by Mark L. Murphy, (Apress, amazon link) ◦ “Pro Android”, by Sayed Y. Hashimi, Satya Komatineni, (Apress, amazon link)