Java Tutorial/J2ME/MIDlet

A first MIDlet with simple text and a few commands

/* License
 * 
 * Copyright 1994-2004 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  
 *  * Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *  * Redistribution in binary form must reproduce the above copyright notice,
 *      this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *  
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *  
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility. 
 */
import javax.microedition.lcdui.rumand;
import javax.microedition.lcdui.rumandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.TextBox;
import javax.microedition.midlet.MIDlet;
// A first MIDlet with simple text and a few commands.
public class SimpleTextCommandMIDlet extends MIDlet implements CommandListener {
  // The exit, info, and buy commands
  private Command exitCommand;
  private Command infoCommand;
  private Command buyCommand;
  // The display for this MIDlet
  private Display display;
  public SimpleTextCommandMIDlet() {
    display = Display.getDisplay(this);
    exitCommand = new Command("Exit", Command.SCREEN, 1);
    infoCommand = new Command("Info", Command.SCREEN, 2);
    buyCommand = new Command("Buy", Command.SCREEN, 2);
  }
  // Start the MIDlet by creating the TextBox and
  // associating the exit command and listener.
  public void startApp() {
    TextBox t = new TextBox("FirstMIDlet", "Welcome to MIDP Programming", 256,
        0);
    t.addCommand(exitCommand);
    t.addCommand(infoCommand);
    t.addCommand(buyCommand);
    t.setCommandListener(this);
    display.setCurrent(t);
  }
  // Pause is a no-op because there are no background
  // activities or record stores to be closed.
  public void pauseApp() {
  }
  // Destroy must cleanup everything not handled
  // by the garbage collector.
  // In this case there is nothing to cleanup.
  public void destroyApp(boolean unconditional) {
  }
  // Respond to commands. Here we are only implementing
  // the exit command. In the exit command, cleanup and
  // notify that the MIDlet has been destroyed.
  public void commandAction(Command c, Displayable s) {
    if (c == exitCommand) {
      destroyApp(false);
      notifyDestroyed();
    }
  }
}

detect and report MIDlet run-time environment

/* License
 * 
 * Copyright 1994-2004 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  
 *  * Redistribution of source code must retain the above copyright notice,
 *  this list of conditions and the following disclaimer.
 * 
 *  * Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the
 *  documentation and/or other materials provided with the distribution.
 * 
 * Neither the name of Sun Microsystems, Inc. or the names of contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *  
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *  
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility. 
 */
/* imports  */
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;
public class J2MEEnvMyMidlet extends MIDlet {
  /**
   * PropertyOutput - lookup and report one application property.
   */
  private void PropertyOutput(String key) {
    String value = getAppProperty(key);
    if (value != null)
      System.out.println(key + " = " + value);
  }
  /**
   * PropertyReport - detect and report MIDlet run-time environment.
   */
  private void PropertyReport() {
    final int Npush = 10; /* maximum number of Push"s to report */
    final int Nmidlet = 10; /* maximum number of MIDlet"s to report */
    final String key[] = { /* standard names */
    "MIDlet-Name", "MIDlet-Version", "MIDlet-Vendor", "MIDlet-Icon",
        "MIDlet-Description", "MIDlet-Info-URL", "MIDlet-Jar-URL",
        "MIDlet-Jar-Size", "MIDlet-Data-Size", "MicroEdition-Profile",
        "MicroEdition-Configuration", "MIDlet-Permissions",
        "MIDlet-Permissions-Opt", "MIDlet-Install-Notify",
        "MIDlet-Delete-Notify", "MIDlet-Delete-Confirm", null };
    final String push_key = "MIDlet-Push-";
    final String midlet_key = "MIDlet-";
    int i;
    for (i = 0; key[i] != null; ++i)
      /* report standard properties */
      PropertyOutput(key[i]);
    for (i = 1; i <= Npush; ++i)
      /* report push entries */
      PropertyOutput(push_key + i);
    for (i = 1; i <= Nmidlet; ++i)
      /* report MIDlet entries */
      PropertyOutput(midlet_key + i);
    return;
  }
  /**
   * MyMIDlet - constructor
   */
  public J2MEEnvMyMidlet() {
    PropertyReport();
  }
  /**
   * startApp - MIDlet has entered the Active state.
   */
  public void startApp() {
  }
  /**
   * pauseApp - enter the Paused state.
   */
  public void pauseApp() {
  }
  /**
   * destroyApp - enter the Destroyed state.
   * 
   * @param unconditional
   */
  public void destroyApp(boolean unconditional)
      throws MIDletStateChangeException {
    if (unconditional == false) {
      throw new MIDletStateChangeException();
    }
  }
}
/*
Running with storage root C:\Documents and Settings\Administrator\j2mewtk\2.5.2\appdb\MediaControlSkin
Running with locale: English_United States.1252
Running in the identified_third_party security domain
No audio device found.
MIDlet-Name = Main Midlet Suite
MIDlet-Version = 1.0.0
MIDlet-Vendor = Midlet Suite Vendor
MIDlet-Jar-URL = Main.jar
MIDlet-Jar-Size = 1691
MicroEdition-Profile = MIDP-2.0
MicroEdition-Configuration = CLDC-1.1
Execution completed.
3399135 bytecodes executed
166 thread switches
1667 classes in the system (including system classes)
17751 dynamic objects allocated (535200 bytes)
2 garbage collections (457948 bytes collected)
*/

extends MIDlet

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.TextBox;
import javax.microedition.midlet.MIDlet;
public class J2MEHiSmallWorld extends MIDlet {
  private TextBox textbox;
  public J2MEHiSmallWorld() {
    textbox = new TextBox("", "Hi Small World!", 20, 0);
  }
  public void startApp() {
    Display.getDisplay(this).setCurrent(textbox);
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
}

KVM Properties

public class KVMProperties {
    private static final String[] properties = {
        "microedition.configuration",
        "microedition.encoding",
        "microedition.platform",
        "microedition.profiles"
    };
    
    public static void main(String[] args) {
        for (int i = 0; i < properties.length; i++) {
            System.out.println(properties[i] + " = " +
                                System.getProperty(properties[i]));
        }
    }
}

list Capabilities

import javax.microedition.lcdui.Choice;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.List;
import javax.microedition.midlet.MIDlet;
public class CapabilitiesMIDlet extends MIDlet {
  private String[] capabilitiesIdx = { "microedition.media.version", "supports.mixing",
      "supports.audio.capture", "supports.video.capture", "supports.recording", "audio.encodings",
      "video.encodings", "video.snapshot.encodings", "streamable.contents" };
  public void startApp() {
    List list = new List("Audio/Video Capabilities", Choice.IMPLICIT);
    for (int i = 0; i < capabilitiesIdx.length; ++i) {
      list.append(System.getProperty(capabilitiesIdx[i]) + " - " + capabilitiesIdx[i], null);
    }
    Display.getDisplay(this).setCurrent(list);
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
}

Retrieving the predefined properties

import java.io.IOException;
import java.io.InputStream;
import javax.microedition.midlet.MIDlet;
public class RuntimeAccessMIDlet extends MIDlet {
  public void startApp() {
    System.out.println("MIDlet-Name: " + getAppProperty("MIDlet-Name"));
    System.out.println("MIDlet-Vendor: " + getAppProperty("MIDlet-Vendor"));
    System.out.println("MIDlet-Version: " + getAppProperty("MIDlet-Version"));
    System.out.println("MIDlet-Description: " + getAppProperty("MIDlet-Description"));
    System.out.println("Target-Devices: " + getAppProperty("Target-Devices"));
    System.out.println("Display-Size: " + getAppProperty("Display-Size"));
    InputStream is = this.getClass().getResourceAsStream("/readme.txt");
    try {
      if (is != null) {
        int character;
        while ((character = is.read()) != -1) {
          System.out.print((char) character);
        }
        is.close();
      }
    } catch (IOException e) {
      System.out.println(e);
    }
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
}

Skeleton of a MIDlet

import javax.microedition.midlet.MIDlet;
public class MyMIDlet extends MIDlet {
  public MyMIDlet() {
    // constructor
  }
  public void startApp() {
    // entering active state
  }
  public void pauseApp() {
    // entering paused state
  }
  public void destroyApp() {
    // entering destroyed state
  }
}