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Writing Your First MIDlet Running JAVA on a Cell Phone

Writing Your First MIDlet Running JAVA on a Cell Phone. Jon A. Batcheller January 27, 2004. Overview. The MID The CLDC & MIDP API Developing Code Emulation Deployment. MID – Mobile Information Device. Cell Phones, Palms, Blackberry…. Pocket Fisherman?

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Writing Your First MIDlet Running JAVA on a Cell Phone

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  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

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

  6. CLDC • 128K to 512K total memory • Limited Power • Limited Connectivity (9600bps) • Reduced UI • Cell Phones, Pagers, PDA’s

  7. 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

  8. 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

  9. 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

  10. MIDlet Lifecycle

  11. 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

  12. 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

  13. Display Object • Displayable current = Display.getDisplay(this).getCurrent(); • Returns current Displayable • Typically in startApp(), look for current Displayable, if null, create own and set it as current.

  14. HelloScreen • Displayable current = Display.getDisplay(this).getCurrent(); • Returns current Displayable • Typically in startApp(), look for current Displayable, if null, create own and set it as current.

  15. HelloMIDlet.java • Compile • Note project library • Package • Emulate • Deploy • Test

  16. Package • JAD • Versions – JAD, CLDC, MIDP • Multiple MIDlets – Suites • Other Classes • Other Files • JAR

  17. 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

  18. 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

  19. Deploy • JAD first • JAR on request • Methods • IR • BlueTooth • Email • WEB – “Over the Air” http://www.javac.com/index.wml

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

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

  22. PropExample.java • Review Code • Emulators • Test

  23. javax.microedition.lcdui • MIDP Low & High-level APIs Displayable Screen Canvas Alert Form List TextBox

  24. javax.microedition.lcdui • Contents of Form and Alert Screens Item ChoiceGroup DateField Gauge ImageItem StringItem TextField

  25. UiDemo.java • Look and Feel • Bejeweled

  26. 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

  27. javax.microedition.io • HttpExample.java • Log & Server2.java

  28. javax.microedition.rms • Named record store • Access to byte array records • Add, Get, Store • Stock Ticker

  29. Writing Your First MIDletRunning JAVA on a Cell Phone And the discussion continues at McMenamin’s Greenway Pub, 12272 SW Scholls Ferry Road North on 217 next exit, then West

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