Michael Brockway

Advanced Applications Development in Java

J2ME -- Introduction

Introduction / Overview Java 2 Micro Edition

CLDC MIDP

Examples

2

Java 2 Micro Edition -- CLDC

A version of the Java platform which supports small devices -- hand-helds, cell phones, pagers, embedded systems, ...

The Connected Limited Device Configuration (CLDC) a set of APIs for applications for devices with limited screens size, memory,

power, bandwidth. Contains the kilobyte virtual machine (KVM) packages java.io, java.lang, java.util

small subsets of the corresponding J2SE packages See java.sun.com/j2me/docs/pdf/cldcapi.pdf for details Package java.io contains

interfaces DataInput, DataOutput classes InputStream, OutputStream

DataInputStream, DataOutputStreamByteArrayInputStream, ByteArrayOutputStreamInputStreamReader, OutputStreamReaderPrintStreamReader Writer

exception, error classes etc

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J2ME -- CLDC

The Connected Limited Device Configuration (CLDC) Package java.lang contains

interface Runnable classes Boolean Byte Character Class

Integer Long Math ObjectRuntime Short String StringBuffer

System Thread Throwable Package java.util contains

interface Enumeration classes Calendar Data Hashtable

Random Stack TimerTimerTask TimeZone Vector

CLDC version 1.0 contained no floating point types, no serializable objects no thread groups no JNI

CLDC 1.1 which appeared in March 2004 contains more features, including floating point arithmetic support

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J2ME -- MIDP

The Mobile Information Device Profile APIs for programming mobile devices -- phones, Palm Pilots, ...

Application software in MIDlets

Package javax.microedition.lcdui contains GUI classes for devices with LCD screens

interfaces Choice CommandListenerItemListener

classes Alert AlertType CanvasChoiceGroup

Command DataField Display Displayable

Font Form Gauge GraphicsImage ImageItem Item ListScreen ScreenItem TextBox TextFieldTicker

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J2ME -- MIDP

The Mobile Information Device Profile (ctd)

Package javax.microedition.io contains support for networking - interfaces Connection ContentConnection

Datagram DatagramConnectionHttpConnection InputConnectionOutputConnection StreamConnection StreamConnectionNotifier

class Connector

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J2ME -- MIDP

The Mobile Information Device Profile Package javax.microedition.rms contains support for local storage -

interfaces RecordComparitor RecordEnumerationRecordFilter RecordListener

class RecordStore

Package javax.microedition.midlet contains the MIDlet class

The minimum hardware for a MIDlet: at least 96 X 54 pixels monochrome display a two-way wireless network an input device 128 kb for CLDC & MIDP classes at least 32 kb for the KVM

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Graphics in a MIDlet

<<interface>>javax.microediiton.lcdui.Displayable

<<abstract>> Screen

<<abstract>>Canvas

Alert TextBox List Form

(low-level)

(high-level)

Canvas is “low leve1” not a container, but we can override its paint method to use Graphics draw

methods Screen is “high level”

a container of laid-out components

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Practicalities

Download the J2ME Wireless Toolkit from http://java.sun.com/products/j2mewtoolkit/index.html Install in Windows or Linux Documentation accompanies the software

Look at the tutorial material in http://developers.sun.com/techtopics/mobility/learn/ Especially MIDlet Life Cycle and Getting Started with MIDP.

Exercises Make a MIDlet which will display a multiplication table when an integer

between 1 and 12 is input. Make a MIDlet which will do simple (+, -, X, /) calculations on two input

numbers