Development of Java ME

(1)

Y3

9

9 PDA

PDA

D

evelopment of Java ME

application

Jan

Jan VystrVystrččil_il

Č_{eské vysoké u}č_{ení technické v Praze}

(2)

Content

What is Java ME

Low Level a High Level API

What is JSR

LBS

(3)

Jan Vystrčil

Development of Java ME application

3/29

Is Java ME still important?

(4)

What is Java ME?

Officially Java Platform, Micro Edition Formerly known as J2ME,

Platform for devices with limited computing power

– Cell phones

– Handheld devices – Industrial controls – Set-top boxes

(5)

Jan Vystrčil

(6)

What is KVM?

KVM – virtual machine for mobile devices Supports only subset of JVM functions

– For ex. no floating point operation support

Written in C

K in KVM stands for Kilobyte

– Running on kilobytes of memory

(7)

Jan Vystrčil

7/29

Configurations CDC and CLDC

CDC - Connected Device Configuration

CLDC - Connected, Limited Device

(8)

Configuration CDC

Using full Java VM Typical requirements

– 32-bit processor

– Minimum 512K for the runtime environment – at least 256K to hold and run applications.

(9)

Jan Vystrčil

9/29

Configuration CLDC

Using KVM

Typical requirements

– 160 to 512 KB total memory available for the Java platform

– 16-bit or 32-bit processor

– low power consumption, often battery powered

– intermittent network connectivity (often wireless) with potentially limited bandwidth

(10)

Profile MIDP

screen size of approximately (at least) 96x54

pixels

display color depth of 1 bit

one- or two-handed keyboard or touch screen

input device

128 KB nonvolatile memory for MIDP components 8 KB nonvolatile memory for application-persistent

data

32 KB volatile runtime memory for Java heap two-way wireless connectivity

(11)

Jan Vystrčil

11/29

Low Level and High Level API

Java ME supports two approaches of GUI

development

– Low Level API

•javax.microedition.lcdui.Canvas

– High Level API

(12)

Difference between Low Level and High Level API (1)

Low Level API

– Fully control graphical design of application (drawing on canvas)

– More difficult application development – Depends on target device (display size) – Limited portability on other devices

– Possible usage of numerical keypad (0-9) for controlling application (keyPressed events)

(13)

Jan Vystrčil

13/29

Difference between Low Level and High Level API

Difference between Low Level and High Level API (2)(2)

High Level API

– Application build up from set of UI components and user controls (forms, text boxes, check boxes etc.)

– Easy and rapid app. development

– Functionality independent on target device

– Easy portability on other devices (high compatibility) – Impossible to fully control graphical design of app.

(depends on device and implementation of MIDP in device) – Impossible -> left/right soft key (controlled by application

manager)

(14)

Difference between Low Level and High Level API

(15)

Jan Vystrčil

15/29

Other

UI

toolkits

Based on Low Level API

(javax.microedition.lcdui.Canvas)

LWUIT

(Lightweight User Interface Toolkit) J2ME Polish

(16)

LWUIT

Inspired by the architecture of Java Swing MVC Features

– Basic set of components – Flexible layouts – Style – Theming Runs on – JavaME – Android – BlackBerry

(17)

Jan Vystrčil

17/29

What is JSR?

JSR = Java Specification Requests

Formal documents that describe proposed

specifications and technologies for adding to the Java platform.

Final JSR provides a reference implementation

that is a free implementation of the technology in source code form and Technology Compatibility Kit to verify the API specification

(18)

(19)

Jan Vystrčil

19/29

Useful

JSR

’

s

JSR 75 - PIM and FileConnection API

– Calendars – Filesystem

JSR 82 - APIs for Bluetooth communication JSR 179 - Location API

– Connection to GPS (A-GPS)

• Internal • Bluetooth

(20)

LBS

–

Location Based Services

Parsing of NMEA-0183 messages

– Used by GPS for communication with other devices – Complicated development

Using Location API (JSR 179) if target device

implements it

(21)

Jan Vystrčil

21/29 NMEA

NMEA -- National Marine Electronics AssociationNational Marine Electronics Association

$GPRMC,162352,A,5053.10,N,00849.14,E,150.0,2 35.3,301294,,*10 $GPRMB,A,0.42,L,EDFN,EDFQ,5102.20,N,00840.80 ,E,010.5,330.1,-018.6,V*08 $GPWPL,5052.50,N,00848.88,E,EDFN*41 $GPGLL,5053.10,N,00849.12,E*6F $PGRMZ,635,f,3*1B $GPXTE,A,A,0.41,L,N*6B $GPBWC,162352,5102.20,N,00840.80,E,330.2,T,, M,010.5,N,EDFQ*3C

(22)

NMEA

NMEA -- National Marine Electronics AssociationNational Marine Electronics Association

NMEA message

$GPGLL,4916.45,N,12311.12,W,225444,A,*1D

Where:

GLL Geographic position, Lat and Lon

4916.46,N Latitude 49 deg. 16.45 min. North

12311.12,W Longitude 123 deg. 11.12 min. West

225444 Fix taken at 22:54:44 UTC

A Data Active or V (void)

(23)

Jan Vystrčil

23/29

LBS

–

using of Location API

...

// Set criteria for selecting a location provider: // accurate to 500 meters horizontally

Criteria cr= new Criteria(); cr.setHorizontalAccuracy(500);

// Get an instance of the provider

LocationProvider lp= LocationProvider.getInstance(cr);

// Request the location, setting a one-minute timeout Location l = lp.getLocation(60);

Coordinates c = l.getQualifiedCoordinates();

if(c != null ) {

// Use coordinate information double lat = c.getLatitude(); double lon = c.getLongitude(); }

(24)

MIDlet

vs. Java ME application

start paused active destroyed startApp() pauseApp() destroyApp() not supported by S40, S60

public class Test extends MIDlet{ private boolean once = false; Pokus() { }

public void startApp() { if ( once == false ) {

once = true;

// resource allocation }

// other resource allocation // logic

}

public void pauseApp() { // resource release }

public void destroyApp() { // all resource release }

(25)

Jan Vystrčil

25/29

MIDlet

vs. Java ME application

start

running

main() class Test extends net.rim.device.api.ui.UiApplication {

public static void main(String[] args) { // resource allocation // logic // resource release } } end

(26)

MIDlet

vs. Java ME application

start paused active destroyed startApp() pauseApp() destroyApp() start running main() end

(27)

Jan Vystrčil

27/29

Java ME

Architecture

for

BlackBerry

HW

Java Virtual Machine

BlackBerry API Java ME API

(MIDP 2.0, CLDC 1.1)

Java Application

Mixing Java ME GUI and BlackBerry GUI not possible • javax.microedition.lcdui

(28)

Java ME code performance

use local variables

– faster access than to class members

use threads for operation longer than 0.1 seconds

– filesystem, network, bluetooth, etc.

access and declaration of data structures

– everything what can be private declare it as private – use final declaration

memory allocation

– do not relay on efficiency of garbage collection

• do not allocate to much memory at once -> reuse objects

– use scalar types (int) instead of objects (Integer)

optimize algorithms

(29)

Jan Vystrčil

29/29

Java ME application deployment

JAR vs. JAD

– JAR: Manifest, Java classes, resource files – JAD: description about Java application

• needed for downloading Java application via network On BlackBerry JAR -> COD

On Android -> MicroEmulator

(30)

More

Resources

and

inspiration

http://pda.felk.cvut.cz

Martin Rýzl - Úvod do Java Micro Edition

(31)

Jan Vystrčil

31/29