workshop - stanislav rost's productions

A Practical WorkshopA Practical Workshop

Stanislav RostCSAIL, MITCSAIL, MIT

INTRODUCTIONWorkshop

INTRODUCTION

About Me

• NAME: Stan Rost• OCCUPATION: Ph.D. Student, Computer Science, MIT

• RESEARCH GROUP: Networks and Mobile Systems (NMS)y

• INTERESTS: Mobile applications, sensor networks, server scalability, P&D

A• ANDROID EXPERIENCE: Principal developer of a social network app, RE:Public ‐‐

Top 100 out of 1788 submissions to Google’s Android p 7 gDesign Challenge; 30+ KLoC, pervasive use of all platform features

RE:Public v1.0

About Me

• NAME: Stan Rost• OCCUPATION: Ph.D. Student, Computer Science, MIT

• RESEARCH GROUP: Networks and Mobile Systems (NMS)

• INTERESTS: mobile applications, sensor networks, server scalability , P&D

• ANDROID EXPERIENCE:ANDROID EXPERIENCE: Principal developer of a social network app, RE:Public ‐‐

Top 100 out of 1788 submissions to Google’s Android Design Challenge; 30+ KLoC pervasive use of all platform featuresChallenge; 30+ KLoC, pervasive use of all platform features

Currently interested in projects on MIDs, phonesW t t l b t th h t QRDC ll b t Want to learn about the research at QRDC, collaborate

Workshop Plan

1• Lecture: platform overview, top‐level components

1p , p p

• Lab: SDK, project development, first sample app

• Lecture: lifecycles, GUI and layout• Lab: first full‐featured application

2

• Lecture: sensors, GPS and maps• Lab: guided development of applications3 g p pp

Pre‐Requisites

RequiredRequired Familiarity with Java Curiosity about mobile software developmenty p Attention to workshop presentations

Preferable Experience with the

Eclipse development environmentEclipse development environment

Disclaimer

Opinions offered in this workshop are my ownOpinions offered in this workshop are my own

Not affiliated with Google

Quanta is “Terra Incognita”Quanta is Terra Incognita

PLATFORM OVERVIEWAndroid

PLATFORM OVERVIEW

Evolution

July 2005 Google acquires the Android company

November 2007 Google announces Android platform,

O d llOpen Handset Alliance

January‐August 2008A d id D i Ch ll t t Android Design Challenge contest

September, October 2008 Android 0 Android 1.0

HTC Dream / T‐Mobile G1

May 2009

Imagesource:richd.com

May 2009 Android 1.5 “Cupcake” released

What is Android?

Android uses the Linux kernel, but is not Linux Tasty bits of kernel: y

threading, MM, networking stack, device drivers BSD‐derived LibC, tuned for embedded devices (200KB)

h ll d d k No shell, X window manager, desktop manager, etc.

Android uses Java but is not a Java platformAndroid uses Java, but is not a Java platform No support for Swing, some other libraries Compiles Java syntax into Dalvik bytecode Compiles Java syntax into Dalvik bytecode Every application runs in its own process, own Dalvik VM Dalvik is register‐based, optimized for small RAM footprintg , p p System hardware is exposed to the VM via Java libraries

Platform Components & Interaction

Included Software Libraries & APIs LibWebCore (WebKit):

modern browser engine + SquirrelFish for JavaScriptSSL d ARM ti i d t SSL and ARM‐optimized crypto

PacketVIDEO’s OpenCore: MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, etc.4, 4, 3, , , , ,

SGL: graphics engine OpenGL ES 1.0 implementation (including in software) SurfaceManager: compositing of layers in display subsys FreeType: bitmap and vector font SQLite: lightweight relational database Google Maps and geocoder

A GPS via LocationManager A‐GPS via LocationManager Nuance Speech Recognition Engine

Supported Hardware

SoC with ARM926 or higher (e.g. ARM11) Must have Linux >2.6.23 running on target with 3 g g

Thumb& MMU & EABI support

SoCmust provide and Linux kernel must support Display frame buffer + double buffering Serial console

K b d Keyboard RTC Storage more than 64MB Storage, more than 64MB SDRAM, more than 32MB USB (optional)( p )

Comparison to Other Mobile PlatformsSources:• Apple Inc.• StrategyAnalyticsy

Feature iPhone 3.0 Android 1.5

Users> 17 million

(19‐24 by end of 2010)> 1 million

(9 ‐ 20 million by 2010)

Apps > 10,000 > 500pp , 5

Distinct features

Push‐based processingFast GPS convergenceProprietary everything

Background processingPhysical keyboardNotification bar

featuresMulti‐touch screenProximity sensor

Home screen widgetsSD card

QUANTA & ANDROID?Entertaining the possibilities

QUANTA & ANDROID?

Three Markets for Android Hardware

Mobile phones A strong, but shy contender g y

Netbooks Hard to see the value proposition relative to x86 netbooks

Hybrid MIDs Tablets / digital frames / readers / home automation / VoIP

Routon 760/730 Nimble Touch Revolution

Considering the Android Platform

•Well‐designed, modern, fast

k d f hi h d

•Who will market the device?

h h d i h b•Makes good use of high‐end phone hardware

•Open source (mostly) open

•The hardware is cheap, but not the cheapest

•Some fragmentation expected•Open‐source (mostly), open

•Very low cost of adoption

•Some fragmentation expected

•Some big‐name competitors already in the market

•Google maintains the ecosystem

already in the market

•Google’s goals, financial incentives unknowny

Ideas for Android Device Makers

Novel hardware features o e a d a e eatu esandsoftware projects that use them in exciting ways develop / sponsor / contribute software

A smart phone or a MIDis an ideal user agent for interfacing with

h ki d f d imany other kinds of devices browsing output of / controlling other devices

Exciting Opportunities

Ultra low‐power, near‐field communication 1000 uses for ad‐hoc protocols; p

would love a ZigBee chip or secondary WiFi

Open peripheral interface HW interface , software stack to work with many sensors,

actuators

Pervasive power management supportPervasive power management support Hardware‐assisted scheduling and “server push”

communicationscommunications

User‐area networks Telephones and MIDs should be central in an ecosystem of p y

wireless sensors, automation devices, proximity beacons

APPLICATION FUNDAMENTALSThe practical portion of the workshop starts here

APPLICATION FUNDAMENTALS

Application Fundamentals Plan

Top Level Components1 Top-Level Components1

Memory Management2

Security3

Concurrency4

Inter-Component Communication5

Top‐Level Application Components

Activity A window of UI elements ; no other component has big UIp g

Service Runs in the background “indefinitely” Can communicate with other components via RPC

BroadcastReceiver Filters system‐wide message broadcasts reacts to some Filters system‐wide message broadcasts, reacts to some

ContentProvider Exposes application’s persistent data to other applications

Activity

A class extending Activity Overrides some methods

Contains Window , UI layout & elements Data structures and data Callbacks for UI & other events

Life cycle Active only when on top May be destroyed at any time

Weather app extends TabActivity, provides Layouts for every tab,

manages custom ListViews

Service

A Persistent Entity Runs in the background of other g

activities, applications

T i f S iTwo primary uses of Services Can host threads that may

block, must live a long timeblock, must live a long time

Can remote procedure call from/to other components

This MP3 player is an Activityp y yBut, a Service plays the MP3 file

Broadcast Receiver

Listens to specific Intents An Intent is an “action” on

“data” (more in later slides)

Receives system‐wide Intents Registers what it listens to via

an IntentFilteran IntentFilter

Short lifespan Only one method Only one method

The Web Browser has a BroadcastReceiver for Intent(ACTION_VIEW, “http://www.google.com”)

Content Provider

Exposes some of an application’s data to other applications Data can be stored in:

fl t fil SQLit t kflat files, SQLite, network

Interface for data accessInterface for data access Apps use ContentResolvers Remote database cursors, ,

update notifications

Contacts is a ContentProvider forCo tacts s a Co te t o de ocontent://contacts/phones

Top‐Level Application Components

Activity A window of UI elements ; no other component has big UIp g

Service Runs in the background “indefinitely” Can communicate with other components via RPC

BroadcastReceiver Filters system‐wide message broadcasts reacts to some Filters system‐wide message broadcasts, reacts to some

ContentProvider Exposes application’s persistent data to other applications

Memory Management and Lifecycles

Most resources are tied to Contexts I.e. the top‐level components which allocated themp p

A component can be paused or destroyed anytime But, not before a warning callback Android provides some support for persisting state

Priority of destruction 1. Background processes in LRU order2. Services3. Foreground processes

Subject of detailed discussion in Session 2

Security and Access Scoping

Private storage A flash chip soldered to the boardp On HTC Dream, 32MB with 10MB available to applications Android uses Linux permissions to prevent runtime access

bto its binaries

Application access scopingApplication access scoping Applications are given private‐access directories Applications cannot access other applications’ private Applications cannot access other applications private

storage Android Market has additional option to encrypt

applications

Concurrency and Multi‐Threading

The top‐level Activity runs in the main application process If you don’t create Threads, the execution is serial*

With the exception*

Why Threads are necessary Android scheduler will offer to KILL any app whose

llb k h d k h d

With the exceptionof some parts of

RPCscallback method takes more than X seconds

Good candidates are network I/O, long calculations

Threads quirksTh d t UI t Threads cannot access UI components

Threads must die with Activity that started them

Inter‐Component Communication

Intents Passive messages that initiate actionsg May include extra data as key‐value pairs

Activity results An Activity can start another Activity for result

Remote procedure calls Used between Activities and Services Used between Activities and Services

ContentProvider queriesq A managed way to access data, including another app’s

Intents

Data structures telling Android to run something Action – what action to perform [+ Category]p g y

(VIEW, EDIT, DIAL, MAIN, etc.) Data – what data to perform it on

(URI like content://contacts/1 )(URI like: content://contacts/1 ) Component – which class to instantiate and run

(Example: com.socialnetwork.EditProfile.class)( p ) Extras – key‐value attributes ≈ Map<String,Object>

(“id” => “12”)

Launch Intents with startActivity(…), startService( ) or broadcastIntent( )startService(…) or broadcastIntent(…)

Intent Example

...// Open the eb bro ser// Open the web browser

URI uri = Uri.parse(“http://www.google.com”);

Intent i =new Intent(Intent.ACTION_VIEW,

uri);

startActivity(i);

...

Activity Results

Activity Results: Start Another Activitypublic class FileUpload extends Activity {

…// In [Browse…] button’s OnClickListenerIntent i = new Intent(this, FileChooser.class);i.putExtra(“initialPath”, currentDirPath);startActivityForResult(i, DEFAULT_REQUEST_CODE);

…

}

Activity Results: Get Intent Arguments

public class FileChooser extends Activity {…

// In onCreate(…)String curPath = getIntent().getStringExtra(“initialPath”);

…

}

Activity Results: Return Results

public class FileChooser extends Activity {

…// In the file list’s selection handlerIntent i = new Intent();i.putExtra(“fileName”,

curFile.getAbsolutePath());setResult(DEFAULT_RESULT_CODE, i);finish();

…}

Activity Results: Process Resultspublic class FileUpload extends Activity {

…@Overridepublic void onActivityResult(int reqCode, int resCode, Intent i) {

Bundle extras = i.getExtras();String chosenFile = extras.getString(“fileName”);// Update the UI with the path of the chosen file…

} …

}

Remote Procedure Calls

A method is called locally, butexecuted remotely in another process Usually, an Activity or a BroadcastReceiver binds to

and calls a ServiceA S i ll b k ALL h ll b d i A Service can call back to ALL the remote callers bound to it

Call arguments are marshalled, queued as messages, dequeued, de‐marshalleddequeued, de marshalled

Carefully consult the documentationy Android Interface Definition Language (AIDL) IBinders, RemoteCallbackList Reuse a lot of the code from examples

ContentProvider Queries

Use a ContentResolver to communicate with the ContactProvider for a specific URI ContentResolvers manage inter‐process communication

in providing access to other application’s data

Use query(…), insert(…), update(…), delete(…) Query results are returned as Managed Cursors –

revitalize automatically when process is killed, then revived

A ContentObserver gets notifications when data is gchanged

LEARNING MORE ABOUT Teach a man to fish, and he shall never be hungry again

LEARNING MORE ABOUT ANDROID

The Documentation

http://developer.android.com/index.html OR <SDK directory>/documentation.html

API Demos

In Eclipse, add demos as a project File > Import > Existing Projects Into Space > Select Root p g j p

Directory … Choose

<SDK Directory>/platforms/android‐1.x/samples/ApiDemos

Useful Websites

Android Developers http://groups.google.com/group/android‐developersp g p g g g p p

Android Issue Tracker http://code.google.com/p/android/issues/list

Android Source Code http://android.git.kernel.org/

Community websitesA d idG Ph d id T lkA d id A d idA h iAndroidGuys Phandroid TalkAndroid AndroidAuthority

Assignment: Focused Research

Find a way to execute a Runnable task periodicallywithin the context of a running Activitythat does not involve Threads

Discover a class that can be used to run an Activity at a specific time in the future

Determine how to start a Service automatically at boot time

Submit by 14:00 to: [email protected] by 14:00 to: [email protected] [xxxxxx] in e-mail title, and your name in body

FIRST STEPS WITH THE Time to use your laptops

FIRST STEPS WITH THE ANDROID SDK

SDK: Installation, Step I

Get Java SDK http://java.sun.com/javase/downloads/index.jspp j j j p Set JAVA_HOME, add JDK’s \bin to PATH

Get Android SDK http://developer.android.com/sdk/1.5_r2/index.html Add SDK’s \bin to PATH

Get Eclipse for Java Developers http://java.sun.com/javase/downloads/index.jsp

Get the Android Plugin for Eclipse In Eclipse, Help > Software Updates > Available

Software > Add Site Software > Add Site … “http://dl‐ssl.google.com/android/eclipse/”

SDK: Installation, Step II

Set up Android SDK location with Android Plugin In Eclipse, p

Window > Preferences … > Android > SDK Location > Browse …, find your SDK directory

Create an Android Virtual Device for the emulator From command line: From command line:android list targetsandroid create avd –n MainPhone –t 2 –c 4096M

Create an Android project in Eclipse File > New > Android Project File > New… > Android Project

Android Project Directory Structure

Your packages and source files


Resource file (auto-generated)

Resource compiler generates unique integer IDs in R.java

for layouts, UI elements, images and other resourcesimages and other resources


The Android class library


Resource Type Directory File

Images res/drawable *.png, *.jpg

Sounds res/raw *.wav,*.mp3

UI Layouts res/layout *.xmly / y

String constants res/values strings.xml

Array constants res/values arrays.xml

Android Project: Adaptive Resources

Layouts and orientations ayouts a d o e tat o sres/layout‐port/ res/layout‐land/

l li iLanguage localizationres/values‐en/ res/values‐de/ res/values‐cn/


Declare top-level components, permissionsp p p

Android Project: Application Manifest

Declare your top‐level components Component receiving intent action MAIN in category p g g y

LAUNCHER starts your program

P i iPermissions <uses‐permission

android:name=“android.permission.INTERNET” />

More examples:CAMERA, ACCESS FINE LOCATION, READ CONTACTS, _ _ , _

Other application propertiespp p p

SDK: Emulator, command‐line tools

Emulation is at ARM hardware level Not emulated: camera, microphone, sensors except GPSp p Real hardware is faster

Android Debug Bridge (adb) Connects to emulator over socket Can upload, install applications,

run a simple Unix‐like shell, show console output

Dalvik Debug Monitor Service (ddms) Inspect memory allocation running processes Inspect memory allocation, running processes Drive emulated telephony, GPS sensor

SDK: Quick Notes On Debugging

In Eclipse, can run the application in “Debug Mode” Set breakpoints, inspect values, step through code Lots of bugs that occur “outside” of your code not easy to

i D b M dsee in Debug Mode

Majority of debugging is done in consoleC d li t l “ db l t” h l t t Command‐line tool “adb logcat” shows console output and trace dumps

“ddms” also shows console output, colorizes depending p , p gon severity

Use Log.d(“tag”, “…”) to output to the console. Also, ( ) ( ) tLog.e(…), Log.w(…) etc.

Summary of Session I

Slides are available for download here:http://www.mit.edu/~stanrost/quanta09/session1/

Topics coveredWhat is Android? What is Android?

Four main Android application component types Resource management in Android OS Resource management in Android OS Communication among the four main component types SDK installation and overview

Next session: Training Room B, 15:00‐16:30 Component lifecycles, GUI design

First Android Application

• Naturally, “Hello World”– Start simplep

– Add a button

– Wire the button to show a Toast

– Add another button, wire to show a Dialog• Receive Dialog response, incorporate in output

workshop - stanislav rost's productions

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