Qusay H. Mahmoud 1

Introduction to Mobile Application Development

Qusay H. Mahmoud, Ph.D.Associate Professor

Department of Computing and Info ScienceUniversity of Guelph, Canada

http://www.cis.uoguelph.ca/~qmahmoud

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Mobile Applications

Mobile Apps are apps or services that can be pushed to a mobile device or downloaded and installed locally.

Classification• Browser-based: apps/services developed in a

markup language• Native: compiled applications (device has a

runtime environment). Interactive apps such as downloadable games.

• Hybrid: the best of both worlds (a browser is needed for discovery)

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Mobile PlatformsA wide variety of devices supporting different

platforms BlackBerry Palm OS Windows Mobile Symbian

Runtime environments & apps Browser-based apps (WAP) Flash-lite Java ME Qualcomm’s BREW Google’s Android

Having a choice is good…but not always… Device fragmentation

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Web Content for Mobile Devices

Markup languages to deliver Web content to device browsers: HDML

Phone.com (now Openwave)

Compact HTML (cHTML)NTT DoCoMo’s i-mode network

WAP Forum’s WMLA standard for content delivered to mobile

devicesNow: openmobilealliance.org

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WAP Network Structure

The WAP Gateway plays an important role

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WAP Programming Model

Similar to the Web programming model with extensions for the wireless environment

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WML Example

<?xml version="1.0"?> <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN" "http://www.wapforum.org/DTD/wml_1.1.xml"> <wml>   <card id="MyFirstCard" title="First Card">     <p align="center">       My First WML Example     </p>   </card>

</wml>

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Java Platform

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Java 2 Platform

Virtual Machines and horizontal and vertical APIs specified in configurations and Profiles

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Configurations

A configuration defines the minimum APIs and VM capabilities for a family of devices: Similar requirements of memory size and

processing capabilitiesThe minimum APIs that an application

developer can expect to be available on implementing devices

May not contain any optional features

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Profiles

A profile is a collection of APIs that supplement a configuration to provide capabilities for a specific vertical market

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How do they fit together?

Profiles are built on top of configurations

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CLDC

Connected Limited Device Configuration Defines APIs and JVM capabilities APIs are subset of Java SE (java.lang, java.util, java.io) Also defines connectivity framework

(javax.microedition, io) but implementation left for profiles

CLDC 1.0 released in May 2000 (no support for floating point numbers). CLDC 1.1 in March 2003

Targets devices (such as cell phones) with: 160 (192) to 512 KB of total memory available for

Java technology Limited power (e.g. battery) Limited connectivity to a network (wireless) Constrained User Interface (small screen)

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MIDP

Targets mobile two-way communication devices implementing the CLDC

Built on top of CLDC to add other functionality like GUI, network implementation, local storage

It addresses: Display toolkit (user input) Persistent data storage HTTP based networking using CLDC generic connection

framework MIDP 1.0 released in December 2000, and MIDP 2.0

in November 2002 MIDP 2.0 new features: support for secure

networking (https), Game API, security mechanisms (code signing)

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KVM

Stands for Kilo Virtual MachineOriginated from a research project

called Spotless at Sun Research LabsImplements the classes defined in the

CLDC specificationNote: the UI classes are not part of the

CLDC

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KVM…

A complete runtime environment for small devices

Built from the ground up in CSmall footprint (40 – 80 KB)Class file verification takes place off-

deviceSupports multi-threadingSupports garbage collection

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KVM Security

VM level security Off-device pre-verification Small in-device verification

Application level security No Security Manager Sandbox security model:

Applications run in a closed environmentApplications can call classes supported by the

device

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Optional Packages

Core MIDP 2.0 functionality is limited. Vendors may include optional packages: JSR-75: File Connection and PIM APIs JSR-82: Bluetooth API JSR-120: Mobile Messaging API JSR-135: Mobile Media API JSR-179: Location API Many others…

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JTWI

JSR-185: Java Technology for Wireless Industry (umbrella specification)

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MSA

JSR-248: Mobile Service Architecture

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Wireless Device Stack

Host OSHost OS

MIDPMIDP

MIDlet

Other Profiles

Other Profiles

Train Schedule

UIHTTP

No floats (CLDC 1.0)KVM

CLDC

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CLDC Internals

The CLDC specification specifies VM features required by a CLDC implementation

Specifies requirements and APIs for Input/Output Networking

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Beyond the CLDC scope

Profiles implemented on top of CLDC specify APIs for: User Interface support Event handling Persistent support High-level application model

An example profile is the Mobile Information Device Profile (MIDP)

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Language & VM Compatibility

Goal: Full Java language and VM specification

compatibilityLanguage-level exception:

No floating point support in CLDC 1.0Manufacturers and developers can include their

own floating point

CLDC 1.1 supports floating point numbers

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CLDC vs. Java SE JVM

Limitations in CLDC supporting JVM: No floating point support (yes in CLDC 1.1) No finalization Limited error handling No Java Native Interface (JNI) No support for reflection No thread groups or daemon threads No weak references (yes in CLDC 1.1) No class loaders Partial bytecode verifier

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CLDC APIs

Classes inherited from J2SE v1.3 are in packages: java.lang java.io java.util

New classes introduced by the CLDC are in package: javax.microedition javax.lang.ref (CLDC 1.1 only)

CLDC 1.1 (JSR 139) has superseded the original CLDC 1.0 spec (JSR 30).

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CLDC Libraries: java.lang.*

BooleanByteCharacterClassIntegerLongMathObjectRunnable

RuntimeShortStringStringBufferSystemThreadThrowable

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CLDC Libraries: java.io.*

ByteArrayInputStreamByteArrayOutputStrea

mDataInputDataOutputDataInputStreamDataOutputStream InputStream

OutputStreamInputStreamReaderOutputStreamWrite

rPrintStreamReaderWriter

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CLDC Libraries: java.util.*

CalendarDateEnumerationHashtableRandomStackTimeZoneVector

No java.util.concurrent (use Threads)

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CLDC 1.0 vs. CLDC 1.1

Very similar. The most important differences are floating-point math capabilities and support for weak references. Classes Float and Double have been added A small subset of Java SE weak-reference

classes

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MIDP internals

Goal: MIDP implementation must fit in small

footprint (128KB ROM) Must run with limited heap size (32-200KB

RAM)

To be implemented by device manufacturers, operators, or developers

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MIDlets

A MIDlet consists of a class that extends the MIDlet class and other classes as needed

To handle events it must implement the CommandListener interface

public class MyMIDlet extends MIDlet implements CommandListener{

}

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MIDP Application Lifecycle

MIDlets move from state to state in the lifecycle: Start: acquire resources and start executing Pause: release resources and wait Destroyed: release all resources and end all

activities Paused

Active

Destroyed

startApp()

destroyApp()

destroyApp()

pauseApp()

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Example MIDlet

import javax.microedition.midlet.MIDlet;import javax.microedition.lcdui.*;

public class FirstMIDlet extends MIDlet { Display display = null; TextBox tb = null; public FirstMIDlet() { display = Display.getDisplay(this); }

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Example MIDlet …

public void startApp() { tb = new TextBox("FirstMIDlet", "Welcome to MIDP Programming", 40, 0); display.setCurrent(tb); }

public void pauseApp() { }

public void destroyApp(boolean unconditional) { } }}

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MIDlet Packaging

Two or mode MIDlets form a MIDlet suiteOne or more MIDlets may be packaged

in a single JAR file that includes: A manifest describing the contents Java classes for the MIDlet(s) Resource file(s) used by the MIDlet(s)

Each jar file is accompanied by a Java Application Descriptor (JAD) file

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MIDlet Packaging

Java Application Descriptor (JAD) file provides info:

Configuration properties Pre-download properties

Size, version, storage requirements

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Example MIDlet…

Compile (javac) Preverify (off device preverification) Create a JAR file: first.jar Create a JAD file: first.jad

MIDlet-Name: MyFirst MIDlet-Version: 1.0.0 MIDlet-Vendor: Sun Microsystems, Inc. MIDlet-Description: My First MIDlet MIDlet-Info-URL: http://java.sun.com/j2me/ MIDlet-Jar-URL: first.jar MIDlet-Jar-Size: 1063 MicroEdition-Profile: MIDP-1.0 MicroEdition-Configuration: CLDC-1.0 MIDlet-1: MyFirst,, FirstMIDlet

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Example MIDlet: Testing

emulator –Xdescriptor first.jad

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MIDlet Example: Deploy

Local: USB, Bluetooth Web:

To deploy a MIDlet on a web server, you need to add a new MIME type:

text/vnd.sun.j2me.app-descriptor jad application/java-archive jar

Create an HTML file with link to the .jar file Use the following command to run:

emulator –Xdescriptor:<JAD file>

Push registry: incoming network connections can launch specific MIDlets

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Simplifying the Development Effort

Sun Java Wireless Toolkit for CLDC

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RIM’s BlackBerry

A smart phoneSelling feature has been instance, secure,

mobile access to emailAttracting a wider range of mobile consumersWell-engineering (consistency across

handhelds)Friction-free path to market applications (no

excessive certification)

Supports Java MERIM’s Java Development Environment (JDE)

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BlackBerry

BlackBerry file format (.cod)RIM’s JDE comes with tools to convert

existing Java ME apps (.jad & .jar) into .cod files

Example: Use rapc to convert .jad & .jar into .cod Use javaloader to load on BlackBerry

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BlackBerry

To utilize BlackBerry-specific features, use BlackBerry APIs

Application lifecycle is different

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BlackBerry

Rest of code…

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MIDP APIs

MIDP specifies APIs for:

User Interface Networking (based on CLDC) Persistent Storage Others…(Game API, security, etc)

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MIDP Packages

MIDP 1.0 java.lang Java.util Java.io Javax.microedition.io Javax.microedition.lcdui Javax.microedition.midlet Javax.microedition.rms

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MIDP Packages

MIDP 2.0 Javax.microedition.lcdui.game Javax.microedition.media Javax.microedition.media.control Javax.microedition.pki

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MIDP User Interface

Not a subset of AWT or Swing because: AWT is designed for desktop computers Assumes certain user interaction models

(pointing device such as a mouse) Window management (resizing overlapping

windows). This is impractical for cell phones

Consists of high-level and low-level APIs

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MIDP UI APIs

High-level API Applications should be runnable and usable

in all MIDP devices No direct access to native device features

Low-level API Provides access to native drawing primitives,

device key events, native input devices Allows developers to choose to compromise

portability for user experience

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MIDP UI Programming Model

The central abstraction is a screenOnly one screen may be visible at a timeThree types of screens:

Predefined screens with complex UI components (List, TextBox)

Generic screens (Form where you can add text, images, etc)

Screens used with low-level API (Canvas)

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MIDP UI and Display

The Display class is the display manager

It is instantiated for each active MIDletProvides methods to retrieve

information about the device’s display capabilities

A screen is made visible by calling: Display’s setCurrent(screen);

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MIDP UI Classes

javax.microedition.lcdui classes:Alert, AlertType, Canvas, ChoiceGroup, Command, DateField, Display, Displayable, Font, Form, Gauge, Graphics, Image, ImageItem, Item, List, Screen, StringItem, TextBox, TextField, Ticker

javax.microedition.lcdui interfaces:Choice, CommandListener, ItemStateListener

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MIDP UI Class Diagram

Major classes and interfaces:

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High-Level API Examples

List:Display display = Display.getDisplay(this);

List menu = new List(“Method of payment”, Choice.EXCLUSIVE);

menu.append(“Visa”);

menu.append(“MasterCard”);

menu.append(“Amex”);

display.setCurrent(menu);

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High-Level API Examples…

Form (Date/Time info):

DateField date = new DateField(“Today’s

date”, DateField.TIME);

Form form = new Form(“Date Info”);

form.append(date);

display.setCurrent(form);

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High-Level Examples…

Form (Sign in screen):Display display = Display.getDisplay(this);TextField userName = new TextField(“LoginID:”, “”,

10, TextField.ANY);TextField password = new TextField(“Password:”, “”,

10, TextField.PASSWORD);Form form = new Form(“Sign in”);form.append(userName);form.append(password);display.setCurrent(form);

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Low-level Example

Canvas:public class MyCanvas extends Canvas {

public void paint(Graphics g) {

g.setColor(255, 0, 0);

g.fillRect(0, 0, getWidth(), getHeight());

g.setColor(255, 255, 255);

g.drawString("Hello World!", 0, 0, g.TOP | g.LEFT);

}

}

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Low-level Example…

Instantiate and display MyCanvaspublic class MyMidlet extends MIDlet { public MyMidlet() { // constructor }  public void startApp() { Canvas canvas = new MyCanvas(); Display display = Display.getDisplay(this); display.setCurrent(canvas); }  // pauseApp() and destroyApp()}

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Input Handling

High-Level API input is handled using abstract commands No direct access to soft buttons Commands are mapped to appropriate soft

buttons or menu items

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Input Handling: Example

TextBox screen with commands:Display display = Display.getDisplay(this);TextBox tb = new TextBox(“MIDP”, “Welcome to MIDP

Programming”, 40, TextField.ANY);Command exit = new Command(“Exit”, Command.SCREEN, 1);Command info = new Command(“Info”, Command.SCREEN, 2);Command buy = new Command(“Buy”, Command.SCREEN, 2);tb.addCommand(exit);tb.addComment(info);tb.addCommand(buy);display.setCurrent(tb);

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Event Handling: High-level

High-level Events:

Based on a listener model Screen objects can have listeners for

commands For an object to be a listener, it must

implement the CommandListener interface This interface has one method: commandAction

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Event Handling: Example

MIDlet implements CommandListenerpublic class MyMIDlet extends MIDlet implements

CommandListener { Command exitCommand = new Command(…); // other stmts public void commandAction(Command c, Displayable s) { if (c == exitCommand) { destroyApp(false); notifyDestroyed(); } }}

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Event Handling: Example

Handling List events:public void commandAction(Command c, Displayable d) { if (c == exitCommand) { ..

} else { List down = (List)display.getCurrent(); switch(down.getSelectedIndex()) { case 0: testTextBox();break; case 1: testList();break; case 2: testAlert();break; case 3: testDate();break; case 4: testForm();break; }

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Event Handling: Low-level

Low-level Events:

Low-level API gives developers access to key press events

Key events are reported with respect to key codes

MIDP defines key codes: KEY_NUM0 .. KEY_NUM9, KEY_STAR, KEY_POUND

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Handling Events: example

Low-level eventsprotected void keyPressed(int keyCode) { if (keyCode > 0) { System.out.println("keyPressed " +((char)keyCode)); } else { System.out.println("keyPressed action “

+getGameAction(keyCode)); } }

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MIDP UI Design Principles

Make the UI simple and easy to useUse the high-level API (portability)If you need to use low-level API, keep

to the platform-independent partMIDlets should not depend on any

specific screen sizeEntering data is tedious, so provide a

list of choices to select from

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Networking

J2SE and J2EE networking APIs are not suitable for handheld devices Require several megabytes of memory to run Device manufacturers who work with circuit-

switched networks require TCP support Device manufacturers who work with packet-

switched networks require UDP support Other devices have specific mechanisms for

communications

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CLDC Generic Connections

A set of related abstractions at the programming level

No abstractions for different forms of communications

All connections are created using the Connector.open()

If successful, it returns an object that implements one of the generic connection interfaces

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Connection Interfaces

MIDP 1.0

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MIDP 2.0

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Example Connections

HTTP: Connector.open(“http://www.host.com”);

Socket: Connector.open(“socket://host.com:80”);

Datagram: Connector.open(“datagram://address:port”);

File: Connector.open(“file:/myfile.txt”);

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Advantages of CLDC Generic Connections

Isolate the differences between the setup of one protocol and another

Most of the application code remains the same regardless of the protocol you use

Note: CLDC itself does not provide any protocol implementation

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MIDP Connectivity

It provides support for HTTP (HttpConnection)

Why? HTTP can be implemented using IP protocols or non-IP protocols

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HttpConnection

Part of the javax.microedition.ioDefines the necessary methods and

constants for an HTTP connection

HttpConnection c = (HttpConnection) Connector.open(“http://quotes.yahoo.com”);

C.setRequestMethod(HttpConnection.POST);C.setRequestProperty(“Content-Language”, “en-CA”);

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Invoking Remote Applications

A MIDlet may invoke remote applications:

Fetching a page Invoking a CGI script (GET or POST

method) Invoking a Servlet

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Example: Invoke a CGI Script

GET Method:

String url = “http://host/cgi-bin/getgrade?idnum=182061”;c = (HttpConnection) Connector.open(url);c.setRequestMethod(HttpConnection.GET);// set some request properties: c.setRequestPropert(“ “, “

“);is = c.openDataInputStream();while((ch = is.read()) != -1) { b.append((char)ch);}

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Example…

If you want to send data to a remote application:

String s = “stuffToSend”;byte postmsg[] = s.getBytes();for(int i=0;i<postmsg.length;i++) { os.writeBytes(postmsg[i]);}// ORos.write(s.getBytes());

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Databases

A persistent storage: a place to store the state of objects

Facilities provided in J2SE and J2EE are not suitable for handheld devices

MIDP provides a record-oriented database mechanism to persistently store data and retrieve it later

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MIDP’s RMS

Lightweight record-oriented database

Device independent API Unique recordID for each record within the

store A record is an array of bytes Shared within MIDlet suite Support for enumeration, sorting, and filtering

javax.microedition.rms

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MIDP RMS Methods

Record StoreopenRecordStore, closeRecordStore, listRecordStore, deleteRecordStore, getRecordSize, getNumRecords

Record DataaddRecord, deleteRecord, getRecord, setRecord, getRecordSize

Record SelectionRecordEnumeration, RecordFilter, RecordComparator

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RMS: Record Stores

To open a record store: RecordStore db =

RecordStore.openRecordStore(“myDB”, true);

To close a record store: db.closeRecordStore();

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Create/Add a new record

To create a new record:

ByteArrayOutputStream baos = new ByteArrayOutputStream()

DataOutputStream dos = new DataOutputStream(baos);

dos.writeUTF(record);Byte b[] = baos.toByteArray();db.addRecord(b, 0, b.length);

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Building a Stock Database

See appendix for source code: Stock.java StockDB.java QuotesMIDlet.java

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StockQuotes MIDlet

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Protection DomainsMIDP provides a security model to prevent

bad MIDlets from misbehavingModel: protection domains (determine what

operations are permitted in a MIDlet) When a MIDlet suite is installed, it goes into

some protection domain (rules to determine what happens when trying to perform a sensitive operation) Net connection (costs money) Reading a file (privacy)

Operation: allowed, denied, user prompted for permission

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Protection Domains

The specification is flexible and leaves manufacturers and carriers room for implementing security models

Implementations vary: Capturing an image restricted on some

devices Playing audio or video restricted on some

deviceMIDlet suites can be signed or unsigned

(different protection domains)

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Protection DomainsWhat to expect?

Un-trusted domain where unsigned MIDlets are denied permission or user promoted for every sensitive operation

Manufacturer or carrier domain: allow MIDlets the most freedom

Identified 3rd party domain: signed MIDlets with keys obtained from known certification authorities (less freedom because no testing or certification by authorized parties)

Devices from different vendors behave differently…

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BlackBerry…

That is why the BLackBerry rules! If your application uses Controlled APIs

(e.g. email), your must sign your application using keys from RIM

Register for keysCost: $100Request through online formTakes a couple of daysCan be used for 1,000,000 signatures

http://www.blackberry.com/SignedKeys

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Java ME Resources Java ME:

http://java.sun.com/j2me Sun Java Wireless Toolkit for CLDC:

http://java.sun.com/products/sjwtoolkit RIM BlackBerry JDE:

http://na.blackberry.com/eng/developers/downloads/jde.jsp

NetBeans: http://www.netbeans.org

JCP:http://www.jcp.org

Resources for academicshttp://www.uoguelph.ca/~qmahmoud/javame & http://cmer.cis.uoguelph.ca

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Thank you

Q&A