Writing Your First MIDlet Running JAVA on a Cell Phone

1
Writing Your First MIDletRunning JAVA on a Cell
Phone

• Jon A. Batcheller
• January 27, 2004

2
Overview

• The MID
• The CLDC MIDP
• API
• Developing Code
• Emulation
• Deployment

3
MID Mobile Information Device

• Cell Phones, Palms, Blackberry.
• Pocket Fisherman?
• JAVA one program, multi-platforms
• similar platforms - WORA

4
MIDP

• Reduced JVM
• J2ME Java 2 Mobile Edition
• CLDC Connected Limited Device Configuration
• CDC Connected Device Configuration full JVM
  imp.
• MIDP Mobile Information Device Profile
• Personal Java, Embedded Java, JavaPhone

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MIDP
JAVA MIDP Apps
MIDP
CLDC
Native Apps
MID Native (SYMBIAN OS)
MID
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CLDC

• 128K to 512K total memory
• Limited Power
• Limited Connectivity (9600bps)
• Reduced UI
• Cell Phones, Pagers, PDAs

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MIDP

• API and virtual machine to device domain
• java.lang
• java.util
• java.io
• javax.microedition.io
• javax.microedition.lcdui
• javax.microedition.rms
• javax.microedition.midlet

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Development Tools

• Sun Micro J2ME Wireless Toolkit
• MIDP 1.0.3
• Borland Sun Forte
• Nokia Standalone JBuilder attachment
• Need environment to compile (library), verify,
  package, emulate, and finally deploy

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Writing our first MIDlet

• Application written for the MIDP Profile
• Must derive from javax.microedition.midlet.MIDlet
• Must implement startApp(), pauseApp() and
  destroyApp()
• Typically also implement a default constructor
  and a commandAction() from the CommandListener
  interface

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MIDlet Lifecycle
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HelloMIDlet.java

• Extends MIDlet
• Implements startApp, pauseApp, destroyApp
• Like an Applet, need something and somewhere to
  display
• Display .vs. Displayable
• Foreground .vs. Background
• Current Displayable

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HelloMIDlet.java

• Extends MIDlet
• Implements startApp, pauseApp, destroyApp
• Like an Applet, need something and somewhere to
  display
• Display .vs. Displayable
• Foreground .vs. Background
• Current Displayable

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Display Object

• Displayable current Display.getDisplay(this).get
  Current()
• Returns current Displayable
• Typically in startApp(), look for current
  Displayable, if null, create own and set it as
  current.

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HelloScreen

• Displayable current Display.getDisplay(this).get
  Current()
• Returns current Displayable
• Typically in startApp(), look for current
  Displayable, if null, create own and set it as
  current.

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HelloMIDlet.java

• Compile
• Note project library
• Package
• Emulate
• Deploy
• Test

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Package

• JAD
• Versions JAD, CLDC, MIDP
• Multiple MIDlets Suites
• Other Classes
• Other Files
• JAR

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JAD Java Application Descriptor

• Usually a link on a WAP site
• Info on the MIDlet
• Most Important URL of the JAR
• Downloaded to MID then user queried to download
  JAR

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JAD Java Application Descriptor

• MIDlet-Name HelloWorld
• MIDlet-Version 0.0.1
• MIDlet-Vendor Solidware, Inc
• MicroEdition-Profile MIDP-1.0
• MicroEdition-Configuration CLDC-1.0
• MIDlet-Jar-URL HelloWorld.jar
• MIDlet-Jar-Size 1592
• MIDlet-1 HelloWorldApp, , HelloWorldApp

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Deploy

• JAD first
• JAR on request
• Methods
• IR
• BlueTooth
• Email
• WEB Over the Air
• http//www.javac.com/index.wml

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Emulate

• Emulators part of toolkits Sun or Phone
• http//developers.sun.com/techtopics/mobility/midp
  /articles/emulators
• Debugging Environment
• Interesting Behaviors

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Test

• Test
• Download jad
• Queries user if new or different version
• Download jar
• Execute Application
• Review Application details

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PropExample.java

• Review Code
• Emulators
• Test

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javax.microedition.lcdui

• MIDP Low High-level APIs

Displayable
Canvas
Screen
Alert
Form
List
TextBox
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javax.microedition.lcdui

• Contents of Form and Alert Screens

Item
ChoiceGroup
DateField
Gauge
ImageItem
StringItem
TextField
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UiDemo.java

• Look and Feel
• Bejeweled

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javax.microedition.io

• CLDC HTTP protocol!
• Connection object
• Content, Datagram, HTTP, Stream
• Normal Stream I/O
• Open with URL
• Get input/output streams
• Read/Write
• Close

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javax.microedition.io

• HttpExample.java
• Log Server2.java

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javax.microedition.rms

• Named record store
• Access to byte array records
• Add, Get, Store
• Stock Ticker

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Writing Your First MIDletRunning JAVA on a Cell
Phone

• And the discussion continues at McMenamins
  Greenway Pub, 12272 SW Scholls Ferry Road
• North on 217 next exit, then West