instructor: mazhar hussain · instructor: mazhar hussain. previous lecture ... v. 2.0)...

PROGRAMMING WITH ANDROID:

SYSTEM ARCHITECTURE

&

MOBILE IP

Instructor: Mazhar Hussain

PREVIOUS LECTURE

•Desktop and Service side Programming

•Software design concerns

2

3

OUTLINE

Android Components: Content Providers

Android Components: Services

Android Components: Intents

Android Components: Activities

Android Dalvik Java Virtual Machine

Android Architecture: An Overview

Android Application Distribution and Markets

4

ANDROID … WHAT?Android is a Linux-based

platform for mobile devices …

Operating System

Middleware

Applications

Software Development Kit (SDK)

Which kind of mobile devices … (examples)

SMARTPHONES TABLETS EREADERS ANDROID TV GOOGLE GLASSES

?

5

ANDROID … WHEN?

Google buys Android from the Android

Inch

Open Handset Alliance (OHA) created for

open standards for mobile devices. Partners of

OHA: Google, Motorola, Samsung, Vodafone, T-

Mobile, etc

Android 1.0 Released

The first Android smartphone: G1 HTC-Dream

Android 1.1 Released

Android 1.5 (CupCake) Released

2005

2006

2007

2008

2009

Time

6

ANDROID … WHEN? Android 1.6 (Donut) Released

Android 2.0 (Eclair) Released

Android 2.2 (Froyo) Released

Android 2.3 (Gingerbread) Released

Android 3.0 (Honeycomb) Released

(First version for devices with larger screens such as tablets)

Android 4.0 (Ice-Cream Sandwich)

Released. (It merges the 3.x tab centric design and the

v2.x phone based design into a single version.)

2008

2009

2010

2011

2012

Time

7

ANDROID … WHEN? Android 4.2 (Jelly Bean) Released

Gesture Mode for Accessibility

Improved browser performance

Easy data-sharing through NFC

Improved camera and face recognition

functionalities

…

API Level 17 (Android 4.2):

Daydream: screensaver customization API

Support to multi-user environments

Nested fragments for UI improvements

…

2012

2013

Time

KEY LIME PIE

8

ANDROID … WHEN?

http://developer.android.com/about/dashboards/index.html http://www.appbrain.com/stats/android-market-

app-categories

ANDROID DISTRIBUTIONS ANDROID APPLICATIONS

x

9

ANDROID … WHEN?

ANDROID VERSION

HISTORY AND POPULARITY

(2009-2013)

http://en.wikipedia.org/wiki/Android_version_history

2.3.x

2.2.x1.6-2.0

4.x

10

THE ANDROID ARCHITECTURE

} Stack

Architect

ure

Open Source

Architecture

(Apache/MIT License

v. 2.0)

Business-friendly

License

11

THE ANDROID ARCHITECTURE

Built on top of

Linux kernel

(v. 2.6-3.0)

Advantages:

Portability (i.e.

easy to compile on

different harwdare

architectures)

Security (e.g.

secure multi-process

environment)

Power

Management

12

THE ANDROID ARCHITECTURE Native

Libraries (C/C++ code)

Graphics (Surface

Manager)

Multimedia (Media

Framework)

Database DBMS (SQLite)

Font

Management (FreeType)

WebKit

C libraries (Bionic)

….

13

THE ANDROID ARCHITECTUREApplication

Libraries(Core Components of

Android)

Activity

Manager

Packet Manager

Telephony

Manager

Location

Manager

Contents

Provider

Notification

Manager

….

14

THE ANDROID ARCHITECTURE

Applications(Written in Java code)

Android Play

Store

Entertainment

Productivity

Personalization

Education

Geo-

communication

….

15

THE ANDROID ARCHITECTURE

Dalvik

Virtual

Machine (VM)

Novel Java

Virtual Machine

implementation (not

using the Oracle

JVM)

Open License

(Oracle JVM is not

open!)

Optimized for

memory-constrained

devices

Faster than

16

DALVIK JAVA VIRTUAL MACHINE (JVM)Java

Source

Code

Java Byte

Code

Java

Virtual

Machine

(JVM)

Java

Source

Code

Java Byte

Code

Dalvik

Byte

Code

Dalvik

Virtual

Machine

(VM)

Java

Compiler

Java

Compiler

Dex

CompilerStack-based

byte-code

Register-based

byte-code

Java Standard Edition

17

ANDROID APPLICATIONS DESIGN

GUI Definition

Events Management

Application Data

Management

Background Operations

User Notifications

APPLICATION DESIGN:

18

ANDROID APPLICATIONS DESIGN

Activities

Intents

Services

Content Providers

Broadcast Receivers

APPLICATION COMPONENTS

19

ANDROID COMPONENTS: ACTIVITIES

An Activity corresponds to a

single screen of the

Application.

An Application can be composed of

multiples screens (Activities).

The Home Activity is shown

when the user launches an

application.

Different activities can exhange

information one with each other.

Hello World!

Android

HelloWorld

Button1

20

ANDROID COMPONENTS: ACTIVITIES

Each activity is composed by a list of graphics

components.

Some of these components (also called Views)

can interact with the user by handling events

(e.g. Buttons).

Two ways to build the graphic interface:

Example:

Button button=new Button (this);TextView text= new TextView();text.setText(“Hello world”);

PROGRAMMATIC APPROACH

21

ANDROID COMPONENTS: ACTIVITIES

Each activity is composed by a list of graphics

components.

Some of these components (also called Views)

can interact with the user by handling events

(e.g. Buttons).

Two ways to build the graphic interface:

Example:

< TextView android.text=@string/hello”android:textcolor=@color/blue android:layout_width=“fill_parent”android:layout_height=“wrap_content” />< Button android.id=“@+id/Button01”android:textcolor=“@color/blue”android:layout_width=“fill_parent”android:layout_height=“wrap_content” />

DECLARATIVE APPROACH

22

- Build the application

layout through XML files(like HTML)

- Define two different XML

layouts for two different

devices

- At runtime, Android

detects the current device

configuration and loads

the appropriate resources

for the application

- No need to recompile!

- Just add a new XML file

if you need to support a

EXAMPLE

Device 1HIGH screen pixel density

Device 2LOW screen pixel density

XML Layout FileDevice 1

XML Layout FileDevice 2

Java App Code

ANDROID COMPONENTS: ACTIVITIES

23

ANDROID COMPONENTS: ACTIVITIES

Android applications typically use both the

approaches!DECLARATIVE

APPROACH

PROGRAMMATIC APPROACH

Define the Application

layouts and resources

used by the Application

(e.g. labels).

Manages the events, and

handles the interaction

with the user.

XML Code

Java Code

24

ANDROID COMPONENTS: ACTIVITIES

Views can generate events (caused by

human interactions) that must be managed by

the Android-developer.

public void onClick(View arg0) {if (arg0 == Button) {

// Manage Button events}

}

ESEMPIO

Bu

tton

TextE

dit

25

ANDROID COMPONENTS: ACTIVITIES

The Activity Manager is

responsible for creating,

destroying, managing activities.

Activities can be on different

states: starting, running,

stopped, destroyed, paused.

Only one activity can be on the

running state at a time.

Activities are organized on a

stack, and have an event-

driven life cycle (details later …)

26

ANDROID COMPONENTS: ACTIVITIES

Main difference between Android-programming and

Java (Oracle) -programming:

Mobile devices have constrained resource

capabilities!

Activity lifetime depends on users’ choice (i.e.

change of visibility) as well as on system

contraints (i.e. memory shortage).

Developer must implement lifecycle methods to

account for state changes of each Activity …

27

ANDROID COMPONENTS: ACTIVITIES

public class MyApp extends Activity {

public void onCreate() { ... }

public void onPause() { ... }

public void onStop() { ... }

public void onDestroy(){ ... }

….

}

Called when the Activity

is created the first time.

Called when the Activity

is partially visible.

Called when the Activity

is no longer visible.

Called when the Activity

is dismissed.

28

ANDROID COMPONENTS: INTENTS Intents: asynchronous messages to activate

core Android components (e.g. Activities).

Explicit Intent The component (e.g.

Activity1) specifies the destination of the intent

(e.g. Activity 2).

LOGIN

PASSWO

RD

Logi

n

marco

**********

Welcome Marco!

Login Intent

Activity1

Activity2

29

ANDROID COMPONENTS: INTENTS Intents: asynchronous messages to activate

core Android components (e.g. Activities).

Implicit Intent The component (e.g.

Activity1) specifies the type of the intent (e.g.

“View a video”).

View

Implicit Intent

Activity1

Activity2

Activity2

Multiple choices

might be available

to the user! } Intent-

Filters

30

ANDROID COMPONENTS: SERVICES Services: like Activities, but run in

background and do not provide an user

interface.

Used for non-interactive tasks (e.g.

networking).

Service life-time composed of 3 states:Startin

g

Destroy

ed

Runnin

g

(on background)

onCreate()

onStart()onDestroy()

31

ANDROID COMPONENTS: CONTENT PROVIDERS

Each Android application has its own

private set of data (managed through files or

through SQLite database).

Content Providers: Standard interface

to access and share data among different

applications.

DB

APP

insert

()update()

delete

()query

()

Conte

nt

Provid

er e.g. Photo

Gallery

32

ANDROID COMPONENTS: BROADCAST RECEIVERS

Publish/Subscrib

e paradigm

Broadcast

Receivers: An

application can

be signaled of

external

events.

Notification

types: Call

incoming, SMS

delivery, Wifi

33

ANDROID COMPONENTS: BROADCAST RECEIVERS

class WifiReceiver extends BroadcastReceiver {

public void onReceive(Context c, Intent intent) {

String s = new StringBuilder();

wifiList = mainWifi.getScanResults();

for(int i = 0; i < wifiList.size(); i++){

s.append(new Integer(i+1).toString() + ".");

s.append((wifiList.get(i)).toString());

s.append("\\n");

}

mainText.setText(sb);

}

BROADCAST RECEIVER example

34

ANDROID COMPONENTS: BROADCAST RECEIVERS

public class WifiTester extends Activity {

WifiManager mainWifi;

WifiReceiver receiverWifi;

List<ScanResult> wifiList;

public void onCreate(Bundle savedInstanceState)

{

…

mainWifi = (WifiManager)

getSystemService(Context.WIFI_SERVICE);

receiverWifi = new WifiReceiver();

registerReceiver(receiverWifi, new

IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE

_ACTION));

mainWifi.startScan();

}

BROADCAST RECEIVER example

35

ANDROID COMPONENTS: SYSTEM API

Using the components described so far, Android

applications can then leverage the system API …

Telephony Manager data access (call, SMS, etc)

Sensor management (GPS, accelerometer, etc)

Network connectivity (Wifi, bluetooth, NFC, etc)

Web surfing (HTTP client, WebView, etc)

Storage management (files, SQLite db, etc)

….

SOME EXAMPLEs …

36

ANDROID COMPONENTS: GOOGLE API

… or easily interface with other Google

services:

37

Each Android application is

contained on a single APK file.

Java Byte-code (compiled for

Dalvik JVM)

Resources (e.g. images. videos,

XML layout files)

Libraries (optimal native C/C++

code)

APK

FIL

E

XM

L

File

s

C

Android Application Distribution

38

ANDROID APPLICATION DISTRIBUTION

Each application must be

signed through a key

before being distributed.

Applications can be

distributed via Web or

via Stores.

Android Play Store:

application store run by

Google … but several

other application stores

are available (they are

just normal applications).

39

ANDROID APPLICATION SECURITY

Android applications run with a distinct

system identity (Linux user ID and group

ID), in an isolated way.

Applications must explicitly share

resources and data. They do this by

declaring the permissions they need for

additional capabilities.

Applications statically declare the permissions

they require.

User must give his/her consensus during the

installation.

<uses-permission android:name=“android.permission.IACCESS_FINE_LOCATION" />

<uses-permission android:name=“android.permission.INTERNET" />

ANDROIDMANIFEST.XML

MOBILE NETWORKING THROUGHMOBILE IP

TRULY MOBILE NETWORKING

Provide confident access to the Internet

anytime, anywhere

Reconnection occurs automatically and

noninteractively

Mobility transparent to applications and

higher level protocols such as TCP

TODAY’S INTERNET PROTOCOL

Packets are routed to destinations based on

IP address

APPLY TO MOBILE NETWORKING

APPLY TO MOBILE NETWORKING

128.143.77.84

X

MOBILE IP APPROACH

Mobile IP uses two IP addresses:

Home address: The IP address assigned to the

mobile node, making it logically appear attached to its

home network.

Care-of address: An IP address at the mobile node's

current point of attachment to the Internet, when the

mobile node is not attached to the home network.

MOBILE NETWORK TERMINOLOGY (1)

Home network: The network at which the mobile node

seems reachable, to the rest of the Internet, by virtue of its

assigned IP address.

Foreign network: The network to which the mobile

node is attached when it is not attached to its home

network, and on which the care-of address is reachable

from the rest of the Internet.

MOBILE NETWORK TERMINOLOGY (2)

Home agent: A router on the home network that

effectively causes the mobile node to be reachable at its

home address even when the mobile node is not attached

to its home network.

Foreign agent: A router on the foreign network that can

assist the mobile node in receiving datagrams delivered to

the care-of address.

HOW MOBILE IP WORKS

128.143.77.84

HA

HOW MOBILE IP WORKS

128.143.77.84

HA

FA

Register

Discovery

Discovering the care-of address

Registering the care-of address

Tunneling to the care-of address

AGENT DISCOVERY PROTOCOL

Extends ICMP Router Discovery protocol

ICMP Router Discovery Protocol enables hosts attached

to multicast or broadcast networks to discover the IP

addresses of their neighboring routers.

Agent advertisements: The mobile agent broadcast

agent advertisements at regular intervals.

Agent solicitation: The mobile node broadcast or

multicast a solicitation that will be answered by any

foreign agent or home agent that receives it.

ADVERTISEMENT MESSAGE FORMATS

ICMP Router Advertisement Agent Advertisement extension

Type: 16

R: register required

B: busy

H: home agent

F: foreign agent

M: minimum encapsulation

G: GRE encapsulation

V: Van Jacobson header compression

ADVERTISEMENT MESSAGE FORMATS

ICMP Router Advertisement Prefix Length extension

Type: 19

Prefix Length:network number of the corresponding Router Address listed in the ICMP Router Advertisement portion of the message.

MOBILE NODE MOVE DETECTIONLifetime based

The mobile node record the Lifetime of advertisement message. If it fails to receive another advertisement from the same agent until the the Lifetime expires, it considers to find a new agent.

Network prefixes based

The Prefix-length extension is used to determine if the newly received advertisement is in the same subnet as the mobile node’s current care-of-

address.

REGISTRATION

MH: mobile host; FA: Foreign Agent; HA: Home Address

Exchange of Registration Request and Registration

Reply messages: UDP using well-known port 434

FOREIGN AGENT CONSIDERATION Each foreign agent must be configured with a care

of address

For each pending or current registration, the foreign

agent maintains a visitor list entry containing:

Link-layer source address of the mobile node

The mobile node’s Home Address

The Home Agent address

The identification field

The requested registration Lifetime

The remaining Lifetime of the pending or current

registration

SECURITY CONSIDERATIONS IN REGISTRATION

Danger: Registration Request works remotely to the

home agent to affect the home agent's routing table

Security:

Authentication: Home agents and mobile nodes perform

authentication using MD5 algorithm and key size of 128

bits.

Replay Protection: The Identification field is used to verify

that a registration message has been freshly generated.

timestamp , random number

TUNNELING TO THE CARE OF ADDRESS

CHANGES WITH IP VERSION 6

Route Optimization

When it knows the mobile node's current care-of

address, a correspondent node can deliver packets

directly to the mobile node's home address without

any assistance from the home agent

Security

Strong authentication and encryption features are

included in IP V6

PROBLEMS FACING MOBILE IP

Security issues

Routing inefficiency

Triangle routing

Ingress filtering

User perceptions of reliability

Competition from other protocols

REFERENCE

"Mobile Networking through Mobile IP," C.

Perkins, IEEE Internet Computing, Vol. 2, No. 1,

1998.

"Mobile IP ," C. Perkins, IEEE Communications

Magazine, Vol. 35, No. 5, 1997.

QUESTIONS/COMMENTS?

61