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Mobile Software Development Framework

10/2/2012

Y. Richard Yang

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Admin.

Homework 2

Start to think about project

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Recap: OFDM

Basic: use multiple subcarriers to reduce symbol rate per carrier

Key idea 1: orthogonal subcarriers to avoid inter-carrier-interference (ICI): chose each subcarrier frequency so that an integral number of cycles in a symbol period

Key idea 2: iFFT as an efficient algorithm for modulation on multiple subcarriers

Idea 3: cyclic prefix (guard interval)

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Recap: Summary of Wireless PHY

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Recap: GNURadio

A software development toolkit that provides signal processing blocks to implement software-defined radio systems.

Some key ideas Hybrid software system (Python/C++) Composite pattern to build a hierarchy of blocks

• http://en.wikipedia.org/wiki/Composite_pattern Internal scheduler to orchestrate data flows

among blocks Define gr_block as a reusable base so that

defining a new block typically means only rewrite general_work and forecast

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Recap: TinyOS

A free and open source component based operating system and platform targeting wireless sensor networks (WSNs)

Some design features TinyOS: Generate customized

OS + application: support one appat a time but flexible reprogramming

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TinyOS: Software Concepts

A TinyOS consists of one or more components/modules linked together software components

motivated by hardware component

Each component specifies: it provides some interfaces

• allows other components to control it

also uses some interfaces• control other components

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Interface

An interface declares a set of

functions called commands that provider must implement

another set of functions called events that the interface user must implement

A uses interfaces I1 and I2

B provides I1 C provides I2

commands events commands eventsI1 I2

C provides I3

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Interface: Examples

StdControl.nc

interface StdControl {  command result_t init();  command result_t start();  command result_t stop();}

Timer.nc

interface Timer {

command result_t start(

char type,

uint32_t interval); 

command result_t stop(); 

event result_t fired();

}

ADC.nc

interface ADC {

async command result_t getdata(); 

async command result_t getContinuousData(); 

event result_t dataReady(uint 16_t data);

}

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Example Application

A simple TinyOS application which periodically reads in the light intensity value, computes a moving average, displays it on the LED

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Module: Definition

SenseTaskM.nc

module SenseTaskM {

provides {

interface StdControl;

}

uses {

interface Timer;

interface ADC;

interface StdControl as ADCControl;

interface Leds;

}

}

A uses interfaces I1 and I2

B provides I1 C provides I2

commands events commands eventsI1 I2

C provides I3

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Module: Implementation

Define commands and event

handlers

frame (storage)• statically allocated, fixed

size to know memory requirement and avoid overhead of dynamic allocation

See SenseTaskM.nc

Component

Internal StateInternal Tasks

Commands Events

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Linking Components

Two types of components:

modules: individual components

configurations : assemble components together, connecting interfaces (objects) used by components to interfaces (objects) provided by others

• See SenseTask.nc

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TinyOS Execution Model

A uses interfaces I1 and I2

B provides I1 C provides I2

commands events commands events

C provides I3

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TinyOS Execution Model

Concurrency model: only two threads long running tasks that can be interrupted by hardware

event handlers

Each task is atomic with respect to other tasks run to completion, but can be preempted by events the task scheduler is a simple FIFO scheduler

Tasks perform the primary computation work commands and event handlers post tasks call lower level commands signal higher level events schedule other tasks within a component

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Running tinyOS Program make mica ncc -o main.exe -target=mica SenseTask.nc avr-objcopy --output-target=srec main.exe

main.srec Use uisp to install

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A More Complete Sample Application Sensor network

monitoring monitor temperature and

light conditions periodically transmit

measurements to a base station

sensors can forward data for other sensors that are out of range of the base station

dynamically determine the correct routing topology for the network

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Internal Component Graph

RFM

Radio byte

Radio Packet

UART

UART Packet

I2C

Temp

Light

Active Messages

Clocksbit

byte

packet

Ad hoc Routing Applicationapplication

HW

SW

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Message Send Transition

Total propagation delay up the 5 layer radio communication stack is about 80 instructions

Timing diagram of event propagation

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Evaluation: Storage

Component Name Code Size (bytes)

Data Size (bytes)

RoutingAM_dispatchAM_temperatureAM_lightAMRADIO_packetRADIO_byteRFMLightTempUARTUART_packetI2C

884078

1463563348103108464

196314198

00

328

4040

81111

408

Processor_initTinyOS schedulerC runtime

17217882

3016

0

Total 3450 226

Scheduler only occupies 178 bytes

Complete application only requires 3 KB of instruction memory and 226 bytes of data (less than 50% of the 512 bytes available)

Only processor_init, TinyOS scheduler, and C runtime are required

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Evaluation: Timing

Operations Cost (cycles)

Time (µs)

Normalized to byte copy

Byte copy 8 2 1

Post an Event

Call a Command

Post a task to scheduler

Context switch overhead

10104651

2.52.5

11.512.7

5

1.251.25

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Interrupt (hardware cost) 9 2.25 1

Interrupt (software cost) 71 17.75

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Summary: TinyOS Components

provide commands andrequire callback hooks for event-driven programming

Configurations Link components

TinyOS an app (configuration)

at a time, linkingonly necessary components

Two threads exec one for event one for task

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ADC.nc

interface ADC {

async command result_t getdata(); 

async command result_t getContinuousData(); 

event result_t dataReady(uint 16_t data);

} configuration SenseTask { // this module does not provide any interfaces}implementation{ components Main, SenseTaskM, LedsC, TimerC, DemoSensorC as Sensor;

Main.StdControl -> TimerC; Main.StdControl -> Sensor; Main.StdControl -> SenseTaskM;

SenseTaskM.Timer -> TimerC.Timer[unique("Timer")]; SenseTaskM.ADC -> Sensor; SenseTaskM.Leds -> LedsC;}

Discussion: Compare TinyOS/GNURadio

What are some similar software concepts?

What are some differences?

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Discussion

Can we use GNURadio/TinyOS for writing mobile applications for mobile phones, or in other words, what are missing?

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Java2 Micro Edition (J2ME)

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Outline

Admin and recap Mobile/wireless development framework

GNURadio TinyOS J2ME

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Java Platforms

Java2 is divided into three platforms J2EE (Java2 Enterprise Edition)

• business applications

J2SE (Java2 Standard Edition)• general applications

J2ME (Java2 Micro Edition)• small devices such as mobile phone, PDA, car navigation

Oracle’s claims on Java on mobile devices http://www.java.com/en/about/

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J2ME Basic Concepts: Versioning To accommodate heterogeneous mobile

devices, define configurations and profiles

http://developers.sun.com/techtopics/mobility/getstart/articles/survey/

-A configuration provides fundamental services for a broad category of devices (e.g., lang, io, util)

- A profile supports higher-level services common to a more specific class of devices or market (e.g., life cycle, GUI)

-An optional package adds specialized services that are useful on devices of many kinds, but not necessary on all of them

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J2ME

128-512K mem16-32 bit proc

Upto 2M mem32 bit proc

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Example J2ME Configurations

Connected Limited Device Configuration (CLDC) 160 KB to 512 KB of total memory available 16-bit or 32-bit processor low power consumption and often operating with battery

power connectivity with limited bandwidth examples: cell phones, certain PDAs

Connected Device Configuration (CDC) 2 MB or more memory for Java platform 32-bit processor high bandwidth network connection, most often using

TCP/IP examples: set-top boxes, certain PDAs

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CLDC Available Packages

java.lang java.util java.io javax.microedition.io

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CLDC Classes Boolean Byte Character Class Integer Long Math Object Runnable Runtime Short String StringBuffer System Thread Throwable

Calendar Date Enumeration Hashtable Random Stack TimeZone Vector

ByteArrayOutputStream ByteArrayInputStream DataOuput DataInput DataInputStream DataOutputStream InputStream InputStreamReader OutputStream OutputStreamWriter PrintStream Reader Writer

java.lang java.util java.io

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Example J2ME Profiles

Mobile Information Device Profile (MIDP) GUI, multimedia and game functionality,

end-to-end security, and greater networked connectivity

mobile phones and entry level PDAs

Foundation Profile set of Java APIs that support resource-constrained devices

without a standards-based GUI system

Personal Profile Full set of AWT APIs, including support for applets and Xlets CDC + Foundation Profile + Personal Profile for high-end PDA

…

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Mobile Phone Framework

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MIDP Hardware

Memory (added to CLDC memory) 128 KB non-volatile for MIDP components 8 KB non-volatile for application persistent

data 32 KB volatile for KVM

Display screen 96x54 display depth 1-bit pixel shape (aspect ratio) 1:1

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MIDP Hardware

Input (one or more)one-handed keyboard (ITU-T phone

keypad)two-handed keyboard (QWERTY keyboard)or touch screen

Networking two-way wireless possibly intermittent limited bandwidth

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MIDP Packages

java.io java.lang java.util javax.microedition.io javax.microedition.lcdui javax.microedition.rms javax.microedition.midlet

javax.microedition.lcdui.game javax.microedition.media javax.microedition.media.contr

ol javax.microedition.pki

addition in version 2.0version 1.0

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MIDP Technology Stack

Mobile Information

Device Profile

KVMCLDC = KVM + J2ME Core

APIs in this

example DSP chip(e.g., ARM)

J2ME core APIs

YourMIDlet

Yellow Pages, train schedules and ticketing, games…

UI, HTTP networking...

Threads, no Floats…

32-bit RISC, 256K ROM, 256K Flash, 64K RAM

MIDlet

GUI based

Each MIDP has one instance of Display• Display.getDisplay(this) to get the manager• At any instance of time at most one Displayable

object can be shown on the display device and interact with user– display.setCurrent(<Displayable object>)

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MIDlet

An MIDP application is called a MIDlet similar to the J2SE applet

A MIDlet moves from state to state in the lifecycle, as indicated

start – acquire resources and start executing

pause – release resources and become quiescent (wait)

destroy – release all resources, destroy threads, and end all activity

Pause

Active

Destroyed

startApp

destroyApp

pauseApp

destroyApp

MIDP Visual Display

Each MIDP has one instance of Display

Display.getDisplay(this) to get the manager

At any instance of time at most one Displayable object can be shown on the display device and interact with user• display.setCurrent(<Displayable object>)

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MIDP Visual Display

Displayable Canvas

• GameCanvas

Screen• Alert, List, TextBox, Form

Form can contain multiple form items for organization Labels, Image Items, String Items, Text Fields, Date

Fields, Gauges, Choice Groups

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MIDP: User Interaction

Displayable objects can declare commands and declare a command listener: addCommand(Command cmd) addCommandListener()

Command(<label>, <type>, <priority>) Type: BACK, CANCEL, EXIT, HELP, ITEM, OK, SCREEN, and STOP

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HelloWorldMIDlet.javaimport javax.microedition.midlet.*;import javax.microedition.lcdui.*;

public class HelloWorldMIDlet extends MIDletimplements CommandListener {

private Command exitCommand;private Display display;private TextBox t;

public HelloWorldMIDlet() { display = Display.getDisplay(this);exitCommand = new Command("Exit", Command.EXIT, 2);t = new TextBox(“CS434", "Hello World!", 256, 0);t.addCommand(exitCommand);t.setCommandListener(this);

}public void startApp() { display.setCurrent(t); }public void pauseApp() { }public void destroyApp(boolean unconditional) { }public void commandAction(Command c, Displayable s) {

if (c == exitCommand) {destroyApp(false);notifyDestroyed();

}}

}

MIDP: Persistent State

Record store defined in javax.microedition.rms

Record store identified by name: static String[] listRecordStores();

recordStore = RecordStore.openRecordStore("scores", true);

recordId = addRecord(byte[] data, int offset, int numBytes);

getRecord(int recordId);

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Summary : J2ME

Scale down a popular programming environment to ease learning

Use virtual machines to mask device heterogeneity

Use configuration/profiling to handle device heterogeneity and avoid using lowest common denominator

MIDLet to manage app life cycle Displayable to visual display, commands and

provides command listener Introduce persistent record store

Discussion on J2ME

What designs of J2ME do you like and hence expect newer frameworks (e.g., IOS, Android) may have too?

What features do you think are missing in J2ME?

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Outline

Admin and recap Mobile/wireless development framework

GNURadio TinyOS J2ME Android

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

Android

A mobile OS, application framework, and a set of applications OS

• Customized Linux kernel 2.6 and 3.x (Android 4.0 onwards)

– E.g., default no X Windows, not full set of GNU libs

Application development framework• Based on Java (J2SE not J2ME)• Dalvik Virtual Machine

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Android Architecture

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Poking Android OS

See http://developer.android.com/tools/workflow/index.html

Android SDK Manager (android) to start a simulator

Android debug bridge (adb) can connect to an Android device and start a shell on the device

Application Framework (Android): Key Concepts

Activity View External resources Service Intercommunications

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Communication among apps: - Intent- broadcast- data provider

Activity

A single, focused thing that the user can do.

Interaction with users: creating a window to place UI views

full-screen windows, floating windows, embedded inside of another activity

Android Activity Life cycle

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View

A view component is a building block for user interface components.

Widget Toolbox TextView, EditText, Button, Form,

TimePicker… ListView Layout

• Positions of controls• LinearLayout, Relativelayout

http://developer.android.com/guide/tutorials/views/index.htm

View by XML

Layout of visual interface

Java Code Initialize

Access TextView myTextView =

(TextView)findViewById(R.id.myTextView);

<?xml version=”1.0” encoding=”utf-8”?><LinearLayout xmlns:android=”http://schemas.android.com/apk/res/android” android:orientation=”vertical” android:layout_width=”fill_parent” android:layout_height=”fill_parent”><TextView android:id=”@+id/myTextView” android:layout_width=”fill_parent” android:layout_height=”wrap_content” android:text=”Hello World, HelloWorld”/></LinearLayout>

@Overridepublic void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main);}

main.xml

User Interaction Event

onKeyDown. onKeyUp onTrackBallEvent onTouchEvent

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; }});}

registerButton.setOnClickListener(new View.OnClickListener() { public void onClick(View arg0) {….}}

Example: TipCal

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Application Framework (Android): Key Concepts

Activity and view Visible screen for user interaction

External resources

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External Resources

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Application Framework (Android): Key Concepts

Activity and view Visible screen for user interaction

External resources Service

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Service: Working in Background A basic function of Android Service:

A facility for an application to tell the system about something it wants to be doing in the background (even when the user is not directly interacting with the application).

The system to schedule work for the service, to be run until the service or someone else explicitly stop it.

NO GUI, higher priority than inactive Activities Note

A Service is not a separate process. The Service object itself does not imply it is running in its own process; unless otherwise specified, it runs in the same process as the application it is part of.

A Service is not a thread. It is not a means itself to do work off of the main thread (to avoid Application Not Responding errors).

Application and Component Glues Intent

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

To invoke operations from your own or others Can pass data back and forth between app.

Intent Filter Register Activities, Services, and Broadcast

Receivers as being capable of performing an action on a particular kind of data.

Intent Description <Component name> Action

Data Category, e.g., LAUNCHER

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Intent Usage

Pass to Context.startActivity() or Activity.startActivityForResult() to launch an activity or get an existing activity to do something new.

Pass to Context.startService() to initiate a service or deliver new instructions to an ongoing service. Pass to Context.bindService() to establish a connection

between the calling component and a target service. It can optionally initiate the service if it's not already running.

Pass to any of the broadcast methods (such as Context.sendBroadcast(), Context.sendOrderedBroadcast(), or Context.sendStickyBroadcast()) are delivered to all interested broadcast receivers. Many kinds of broadcasts originate in system code.

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Android: Broadcast Receiver

Sending a broadcast: Context.sendBroadcast(Intent intent, String receiverPermission)

Context.sendOrderedBroadcast()

Receiving broadcast: Intent registerReceiver (BroadcastReceiver receiver, IntentFilter filter)

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Intent Resolution: Explicit

Explicit intents: component identified

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Make sure AndroidManifest.xml announces activities to be started

Intent myIntent = new Intent(IntentController.this, TipCal.class);startActivity(myIntent);

<application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".IntentController" android:label="Intent1"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".TipCal"></activity> </application>

Intent Resolution: Implicit

Implicit intents System matches an intent object to the intent

filters of others

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http://developer.android.com/guide/topics/intents/intents-filters.html

Intent filter

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action

category

data

Intent Example II: Implicit

AndroidManifest.xml file for com.android.browser

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String action = "android.intent.action.VIEW";Uri data = Uri.parse("http://www.google.com");Intent myIntent = new Intent(action, data);startActivity(myIntent);

<intent-filter>    <action android:name="android.intent.action.VIEW" />    <category android:name="android.intent.category.DEFAULT" />    <scheme android:name="http" />    <scheme android:name="https" />    <scheme android:name="file" /></intent-filter>

Intent Example II: Implicit

String action = "android.intent.action.DIAL";String phno = "tel:4326400";Uri data = Uri.parse(phno);Intent dialIntent = new Intent(action, data);startActivity(dialIntent);

A Design Template: Invoker

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String action = “com.hotelapp.ACTION_BOOK";String hotel = “hotel://name/“ + selectedHotel;Uri data = Uri.parse(hotel);Intent bookingIntent = new Intent(action, data);startActivityForResults(bookingIntent, requestCode);

A Design Template: Provider

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<activity android:name=".Booking" android:label=“Booking"> <intent-filter> <action android:name=“com.hotelapp.ACTION_BOOK" /> <data android:scheme=“hotel" android:host=“name”/> </intent-filter></activity>

For more complex data passing, please read the tutorial

A Design Template: Provider

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@Overridepublic void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main);

Intent intent = getIntent(); // why am I called String action = intent.getAction(); Uri data = intent.getdata();

String hotelName = data.getPath(); // do the booking

setResult(RESULT_OK); finish();}

Intent and Broadcast: Sender

String action = "edu.yale.cs434.RUN";

Intent cs434BroadcastIntent = new Intent(action);

cs434BroadcastIntent.putExtra("message", "Wake up.");

sendBroadcast(cs434BroadcastIntent);

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Example: IntentLaunch

Intent and Broadcast: Receiver

<receiver android:name=".CS434BroadcastReceiver" android:enabled="true">

<intent-filter>

<action android:name="edu.yale.cs434.RUN" />

</intent-filter>

</receiver>

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Intent, Broadcast, Receiver, Notificationpublic class CS434BroadcastReceiver extends BroadcastReceiver {

public static final String CUSTOM_INTENT = "edu.yale.cs434.RUN";

// Display an alert that we've received a message.

@Override

public void onReceive(Context context, Intent intent) {

if (intent.getAction().equals(CUSTOM_INTENT)) {

String message = (String)intent.getExtras().get("message");

CharSequence text = "Got intent " + CUSTOM_INTENT + " with " + message;

int duration = Toast.LENGTH_SHORT;

Toast mToast = Toast.makeText(context, text, duration);

mToast.show();

} // end of if

} // end of onReceive

}

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Recap: Do not Block

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ANRs (Application not responding) happen when Main thread (“event”/UI) does

not respond to input in 5 sec A broadcast receiver does

not finish in 10 sec 5-10 sec is absolute upper

bound

Recap: Do not Block

Numbers (Nexus One) ~5-25 ms – uncached flash reading a byte ~5-200+(!) ms – uncached flash writing tiny amount 100-200 ms – human perception of slow action 108/350/500/800 ms – ping over 3G. varies! ~1-6+ seconds – TCP setup + HTTP fetch of 6k over 3G

Rules Notify users Use background processing Example: LaunchThread Example: SimplyService

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Background Processing using a Thread

Problem: Background thread and UI thread are running

concurrently and may have race conditions if they modify simultaneously

Solution: Android Handler Use Handler to send and process Message and

Runnable objects associated with a thread's MessageQueue.

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Android Handler

Each Handler instance is associated with a single thread and that thread's message queue.

A handler is bound to the thread / message queue of the thread that is creating it from that point on, it will deliver messages

and runnables to that message queue and execute them as they come out of the message queue.

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Using Handler

There are two main uses for a Handler: to schedule messages and runnables to be

executed as some point in the future; and to enqueue an action to be performed on a

different thread than your own.

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Handler

public class MyActivity extends Activity {

    [ . . . ]    // Need handler for callbacks to the UI thread    final Handler mHandler = new Handler();

    // Create runnable for posting    final Runnable mUpdateResults = new Runnable() {        public void run() {            updateResultsInUi();        }    };

    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);

        [ . . . ]    }

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Handler

    protected void startLongRunningOperation() {

        // Fire off a thread to do some work that we shouldn't do directly in the UI thread        Thread t = new Thread() {            public void run() {                mResults = doSomethingExpensive();                mHandler.post(mUpdateResults);            }        };        t.start();    }

    private void updateResultsInUi() {

        // Back in the UI thread -- update our UI elements based on the data in mResults        [ . . . ]    }}

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Examples

See BackgroundTimer

See HandleMessage

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Tools

AsyncTask

IntentService

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Tools: AsyncTask

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private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> { protected Long doInBackground(URL... urls) { // on some background thread int count = urls.length; long totalSize = 0; for (int i = 0; i < count; i++) { totalSize += Downloader.downloadFile(urls[i]); publishProgress((int) ((i / (float) count) * 100)); } return totalSize; } protected void onProgressUpdate(Integer... progress) { // on UI thread! setProgressPercent(progress[0]); } protected void onPostExecute(Long result) { // on UI thread! showDialog("Downloaded " + result + " bytes"); }}

new DownloadFilesTask().execute(url1, url2, url3); // call from UI thread!

See GoogleSearch

Does Background Solve All Issues?

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Example: Accessing Data in Cloud

A typical setting is that a device accesses data in the cloud, e.g., background sync

Challenge: How do you keep data on a device fresh?

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Polling

Simple to implement Device periodically asks server for new

data Appropriate for content that changes

constantly Stock Quotes, News Headlines

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Impact of Polling on Battery

Baseline: ~5-8 mA Network: ~180-200 mA

Tx more expensive than Rx Assume radio stays on for 10 sec.

Energy per poll: ~0.50 mAh 5 min frequency: ~144 mAh / day

Droid 2 total battery: 1400 mAh

91Source: Android development team at Google

Solution: Push

Google Contacts, Calendar, Gmail, etc., use push sync

A single persistent connection from device to Google

Android Cloud to Device Messaging (C2DM) to make it a public service

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C2DM Overview

Uses existing connection for Google services

Your servers send lightweight “data” messages to apps

Tell app new data available Intent broadcast wakes up app App supplies UI, e.g., Notification, if/as

necessary

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C2DM Flow

Enabling cloud to device messaging App (on device) registers with Google, gets

registration ID App sends registration ID to its App Server

Per message App Server sends (authenticated) message to

Google Google sends message to device

Disabling cloud to device messaging App can unregister ID, e.g., when user no

longer wants push94

C2DM

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Android Code: Registration to C2DM// Use the Intent API to get a registration ID

// Registration ID is compartmentalized per app/device

Intent regIntent = new

Intent(“com.google.android.c2dm.intent.REGISTER”);

// Identify your app

regIntent.putExtra(“app”,

PendingIntent.getBroadcast(this, 0, new Intent(), 0);

// Identify role account server will use to send

regIntent.putExtra(“sender”, emailOfSender);

// Start the registration process

startService(regIntent);

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Receiving Registration ID

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// Registration ID received via an Intent

public void onReceive(Context context, Intent intent) {

String action = intent.getAction();

if (“…REGISTRATION”.equals(action)) {

handleRegistration(context, intent);

} }

private void handleRegistration(Context context, Intent intent){

String id = intent.getExtra(“registration_id”);

if ((intent.getExtra(“error”) != null) {

// Registration failed. Try again later, with backoff.

} else if (id != null) {

// Send the registration ID to the app’s server.

// Be sure to do this in a separate thread.

} }

Receiving Registration ID

App receives the ID as an Intent com.google.android.c2dm.intent.REGISTRATIO

N App should send this ID to its server Service may issue new registration ID at

any time App will receive REGISTRATION Intent

broadcast App must update server with new ID

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Android: Content Provider

Each provider can expose its data as a simple table on a database model

Each content provider exposes a public URI that uniquely identifies its data set:

android.provider.Contacts.Phones.CONTENT_URI android.provider.Contacts.Photos.CONTENT_URI android.provider.CallLog.Calls.CONTENT_URI android.provider.Calendar.CONTENT_URI

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Intent and Content Provider private void pickContact() {

    // Create an intent to "pick" a contact, as defined by the content provider URI    Intent intent = new Intent(Intent.ACTION_PICK, Contacts.CONTENT_URI);    startActivityForResult(intent, PICK_CONTACT_REQUEST);}

@Overrideprotected void onActivityResult(int requestCode, int resultCode, Intent data) {    // If the request went well (OK) and the request was PICK_CONTACT_REQUEST    if (resultCode == Activity.RESULT_OK && requestCode == PICK_CONTACT_REQUEST) {        // Perform a query to the contact's content provider for the contact's name        Cursor cursor = getContentResolver().query(data.getData(),        new String[] {Contacts.DISPLAY_NAME}, null, null, null);        if (cursor.moveToFirst()) { // True if the cursor is not empty            int columnIndex = cursor.getColumnIndex(Contacts.DISPLAY_NAME);            String name = cursor.getString(columnIndex);            // Do something with the selected contact's name...        }    }}

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Windows .NET Compact Framework Similar to J2ME Scales down a popular programming environment to ease

learning the .NET CF is a subset of the full .NET framework with some additions designed for resource constrained devices 1,400 classes for .NET CF vs. 8,000 for full 27 UI controls for .NET CF vs. 52 for full 1.5 MB for .NET CF vs. 30 MB for full

Uses versioning to avoid using lowest common denominator pocket PC pocket PC phone version smart phone version

Uses virtual machines to mask device heterogeneity programming languages compile to MSIL

• MSIL is JIT compiled on the device• MSIL code is smaller than native executables• MSIL allows your code to be processor independent

Android

Linux kernel as foundation Java based framework (J2SE not J2ME)

Dalvik Virtual machine Nice features

Touch screen, accelerometer, compass, microphone, camera, GPS,

GSM, EDGE, and 3G networks, WiFi, Bluetooth, Near field communications

Media, SQLite, WebKit, SSL Location-based service, map (Google API)

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