Java/J2ME/Event Command

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Accessing Commands

   <source lang="java">

/*--------------------------------------------------

  • AccessingCommands.java
  • Example from the book: Core J2ME Technology
  • Copyright John W. Muchow http://www.CoreJ2ME.ru
  • You may use/modify for any non-commercial purpose
  • -------------------------------------------------*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; public class AccessingCommands extends MIDlet implements CommandListener { 

 private Display display;      // Reference to Display object
 private Form fmMain;         // A Form  
 private Command cmExit;      // A Command to exit the MIDlet
 public AccessingCommands()
 {
   display = Display.getDisplay(this);
   cmExit = new Command("Exit", Command.EXIT, 1);
   fmMain = new Form("Core J2ME");
   fmMain.addCommand(cmExit);
   fmMain.setCommandListener(this);
 }
 // Called by application manager to start the MIDlet.
 public void startApp()
 {
   display.setCurrent(fmMain);
 }
 // A required method
 public void pauseApp()
 { }
 // A required method
 public void destroyApp(boolean unconditional)
 { }
 // Check to see if our Exit command was selected
 public void commandAction(Command c, Displayable s)
 {
   if (c == cmExit)
   {
     destroyApp(false);
     notifyDestroyed();
   }
 }

} 


      </source>



A first MIDlet with simple text and a few commands.

   <source lang="java">

/* 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.midlet.*; import javax.microedition.lcdui.*; // A first MIDlet with simple text and a few commands. public class FirstMIDlet 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 FirstMIDlet() {
   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();
   }
 }

} 


      </source>



An example MIDlet with simple Hello text and an Exit command

   <source lang="java">

/* 

*
* Copyright (c) 2000 Sun Microsystems, Inc. All Rights Reserved.
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information").  You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; /** 

* An example MIDlet with simple "Hello" text and an Exit command.
* Refer to the startApp, pauseApp, and destroyApp
* methods so see how each handles the requested transition.
*/

public class HelloCommandMIDlet extends MIDlet implements CommandListener { 

 private Command exitCommand; // The exit command
 private Command okCommand; // The exit command
 private Command cancelCommand; // The exit command
 private Command nextCommand; // The exit command
 private Command backCommand; // The exit command
   private Display display;  // The display for this MIDlet
   public HelloCommandMIDlet() {
       display = Display.getDisplay(this);
      exitCommand = new Command("Exit", Command.EXIT, 2);
   }
   /**
    * Start up the Hello MIDlet by creating the TextBox and associating
    * the exit command and listener.
    */
   public void startApp() {
       TextBox t = new TextBox("Hello", "Hello World!", 256, 0);
       t.addCommand(exitCommand);
       t.setCommandListener(this);
       display.setCurrent(t);
   }
   /**
    * Pause is a no-op since there are no background activities or
    * record stores that need 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, including exit
    * On 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();
 } 
   }

} 


      </source>



Api concepts Refer to the startApp pauseApp, and destroyApp

   <source lang="java">

/* 

* AdvanceCommands.java 
* Copyright (c) 2000 Sun Microsystems, Inc. All Rights Reserved.
*
* Author: Srikanth Raju
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information").  You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*/

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; /** 

* An MIDlet that illustrates more MIDP UI Api concepts Refer to the startApp,
* pauseApp, and destroyApp methods so see how each handles the requested
* transition.
*/

public class AdvanceCommands extends MIDlet implements CommandListener { 

 private Command exitCommand; // The exit command
 private Command nextCommand; // next command
 private Command backCommand; // back command
 private TextBox t1;
 private TextBox t;
 private Display display; // The display for this MIDlet
 public AdvanceCommands() {
   display = Display.getDisplay(this);
   nextCommand = new Command("Next", Command.SCREEN, 1);
   exitCommand = new Command("Quit", Command.SCREEN, 2);
   backCommand = new Command("Back", Command.BACK, 2);
 }
 /**
  * Start up the Hello MIDlet by creating the TextBox and associating the
  * exit command and listener.
  */
 public void startApp() {
   t = new TextBox("Hello MIDlet", "Test string", 256, 0);
   t.addCommand(nextCommand);
   t.addCommand(exitCommand);
   t.setCommandListener(this);
   display.setCurrent(t);
 }
 /**
  * Pause is a no-op since there are no background activities or record
  * stores that need 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, including exit On 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();
   }
   if (c == nextCommand) {
     t1 = new TextBox("2nd TextBox", "2nd TextBox", 256, 0);
     t1.addCommand(backCommand);
     t1.addCommand(exitCommand);
     t1.setCommandListener(this);
     display.setCurrent(t1);
   }
   if (c == backCommand) {
     display.setCurrent(t);
   }
 }

} 


      </source>



A quick sample of graphics, commands, and event handling.

   <source lang="java">

/* 

* @(#)Sample.java  1.9 01/06/08
* Copyright (c) 1999-2001 Sun Microsystems, Inc. All Rights Reserved.
*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*;

/* 

* A quick sample of graphics,  commands, and event handling.
*/

public class SampleCanvasMIDlet extends MIDlet implements CommandListener { 

   Display display;
   Command exitCommand;
   Command backCommand;
   Command okCommand;
   SampleCanvas sample; // Instance of sample canvas
   List itemMenu;
   List exclusiveList;
   List multipleList;
   TextBox textbox;
   Ticker ticker;
   Alert alert;
   Form form;
   StringItem stringItem;
   ImageItem imageItem;
   Image image;
   TextField textItem;
   ChoiceGroup choiceItem;
   DateField dateItem;
   Gauge gaugeItem;

   public SampleCanvasMIDlet() {
       display = Display.getDisplay(this);
       exitCommand = new Command("Exit", Command.EXIT, 1);
       backCommand = new Command("Back", Command.BACK, 2);
       okCommand = new Command("OK", Command.OK, 3);
       ticker = new Ticker("Select an item to display");
       itemMenu = new List(null, Choice.IMPLICIT);
       itemMenu.append("Canvas", null);
       itemMenu.append("Form", null);
       itemMenu.append("Alert", null);
       itemMenu.append("TextBox", null);
       itemMenu.append("Exclusive List", null);
       itemMenu.append("Multiple Choice", null);
       itemMenu.setCommandListener(this);
       itemMenu.addCommand(exitCommand);
       itemMenu.setTicker(ticker);
       display.setCurrent(itemMenu);
   }
   public void startApp () {
   }
   public void destroyApp (boolean unconditional) {
   }
   public void pauseApp () {
   }
   public void commandAction(Command c, Displayable s) {
       if (c == backCommand) {
           display.setCurrent(itemMenu);
       } else if (s == itemMenu) {
           if (c == List.SELECT_COMMAND) {
               // Handle the item sected to be displayed
               int i = itemMenu.getSelectedIndex();
               switch (i) {
                   case 0: // Show Sample canvas
                       display.setCurrent(getCanvas());
                       break;
                   case 1: // Show the form
                       display.setCurrent(getForm());
                       break;
                   case 2: // Show an alert
                       display.setCurrent(getAlert("Warning", 
                               "This window will dismiss in two seconds."));
                       break;
                   case 3: // Show TextBox
                       display.setCurrent(getTextBox());
                       break;
                   case 4: // Show Exclusive list
                       display.setCurrent(getExclusiveList());
                       break;
                   case 5: // Show Multiple List
                       display.setCurrent(getMultipleList());
                       break;
               }
           } else if (c == exitCommand) {
               notifyDestroyed();
           }
       } else if (s == exclusiveList) {
           int i = exclusiveList.getSelectedIndex();
           String value = exclusiveList.getString(i);
           alert = getAlert("Border selected:", value);
           display.setCurrent(alert, itemMenu);
       } else if (s == multipleList) {
           StringBuffer b = new StringBuffer();
           for (int i = 0; i <= 2; i++) {
               if (multipleList.isSelected(i)) {
                   b.append(multipleList.getString(i));
                   b.append("\n");
               }
           }
           alert = getAlert("Colors selected:", b.toString());
           display.setCurrent(alert, itemMenu);
       } else if (s == textbox) {
           String value = textbox.getString();
           alert = getAlert("Text Entered:", value);
           display.setCurrent(alert, itemMenu);
       } else if (s == form) {
           alert = getAlert("Image options  saved", "");
           display.setCurrent(alert, itemMenu);
       }
   }
   SampleCanvas getCanvas() {
       if (sample == null) {
           sample = new SampleCanvas();
           sample.addCommand(backCommand);
           sample.setCommandListener(this);
       }
       return sample;
   }
   List getExclusiveList() {
       if (exclusiveList == null) {
           exclusiveList = new List("Border Style", Choice.EXCLUSIVE);
           exclusiveList.append("None", null);
           exclusiveList.append("Plain", null);
           exclusiveList.append("Fancy", null);
           exclusiveList.addCommand(backCommand);
           exclusiveList.addCommand(okCommand);
           exclusiveList.setCommandListener(this);
       }
       return exclusiveList;
   }
   List getMultipleList() {
       if (multipleList == null) {
           multipleList = new List("Colors to mix", Choice.MULTIPLE);
           multipleList.append("Red", null);
           multipleList.append("Green", null);
           multipleList.append("Blue", null);
           multipleList.addCommand(backCommand);
           multipleList.addCommand(okCommand);
           multipleList.setCommandListener(this);
       }
       return multipleList;
   }
   TextBox getTextBox() {
       if (textbox == null) {
           textbox = new TextBox("Enter a phone number","", 40,
         TextField.PHONENUMBER);
           textbox.addCommand(backCommand);
           textbox.addCommand(okCommand);
           textbox.setCommandListener(this);
       }
       return textbox;
   }
   
   Alert getAlert(String title, String contents) {
       if (alert == null) {
           alert = new Alert(title);
           alert.setType(AlertType.WARNING);
           alert.setTimeout(2000);
     alert.setString(contents); 
       } else {
           alert.setTitle(title);
           alert.setString(contents);
       }
       return alert;
   }
   
   Form getForm() {
        if (form == null) {
           form = new Form("Options");
           try {
               image = Image.createImage("/images/PhotoAlbum.png");
               imageItem = new ImageItem("Preview:", image, 
                           ImageItem.LAYOUT_NEWLINE_BEFORE, "Mountain");
               form.append(imageItem);
           } catch (java.io.IOException ex) {
           }
           textItem = new TextField("Title:", "Mountain", 32,
            TextField.ANY);
           form.append(textItem);
           
           dateItem = new DateField("Date:", DateField.DATE);
           dateItem.setDate(new java.util.Date());
           form.append(dateItem);
           choiceItem = new ChoiceGroup("Size:", Choice.EXCLUSIVE);
           choiceItem.append("Small", null);
           choiceItem.append("Large", null);
           form.append(choiceItem);
           
           gaugeItem = new Gauge("Speed:", true, 10, 5);
           form.append(gaugeItem);
           form.addCommand(backCommand);
           form.addCommand(okCommand);
           form.setCommandListener(this);
       }
       return form;
   }

}

class SampleCanvas extends Canvas { 

   int     x, y;           // Location of cross hairs
   String  event = "";     // Last key event type
   int     keyCode;        // Last keyCode pressed
   Font    font;           // Font used for drawing text
   int     fh;             // height of the font
   int     w, h;           // width and height of the canvas
   int     titleHeight;    // Height of the title
   int     pieSize;        // Size of the Pie chart used for width and height
   int     barSize;        // Size of the Bar chart used for width and height
   int     eventHeight;    // Size of the event region
   int     pad;            // Padding used between items
   SampleCanvas() {
       w = getWidth();
       h = getHeight();
       font = Font.getFont(Font.FACE_SYSTEM,
         Font.STYLE_PLAIN, Font.SIZE_SMALL);
       fh = font.getHeight();
       /* Compute the sizes of the bar and pie charts
        * It should use all the space except for the title
  * and event regions.
        * Don"t let the charts get too small
        */
       pad = 2;
       titleHeight = fh + pad * 2;
       eventHeight = fh * 3;
       barSize = h - (titleHeight + pad) - (eventHeight + pad);
       if (barSize < 20)               // Don"t let them get too small
           barSize = 20;
       if (barSize > (w - pad) / 2)    // Shrink to 1/2 width
           barSize = (w - pad) / 2;
       pieSize = barSize;
   }
   protected void keyPressed(int key) {
       keyCode = key;
       event = "Pressed";
       handleActions(key);
       repaint();
   }
   protected void keyRepeated(int key) {
       keyCode = key;
       event = "Repeated";
       handleActions(key);
       repaint();
   }
   protected void keyReleased(int key) {
       keyCode = key;
       event = "Released";
       repaint();
   }
   protected void pointerPressed(int x, int y) {
       this.x = x;
       this.y = y;
       keyCode = 0;
       event = "Pressed";
       repaint();
   }
   protected void pointerReleased(int x, int y) {
       this.x = x;
       this.y = y;
       keyCode = 0;
       event = "Released";
       repaint();
   }
   protected void pointerDragged(int x, int y) {
       this.x = x;
       this.y = y;
       keyCode = 0;
       event = "Dragged";
   }
   void handleActions(int keyCode) {
       int action = getGameAction(keyCode);
       switch (action) {
           case LEFT:
           x -= 1;
           break;
           case RIGHT:
           x += 1;
           break;
           case UP:
           y -= 1;
           break;
           case DOWN:
           y += 1;
           break;
       }
   }
   protected void paint(Graphics g) {
       g.setFont(font);
       g.setGrayScale(255);
       g.fillRect(0, 0, w, h);
       x = (x < 0) ? w - 1 : x;
       y = (y < 0) ? h - 1 : y;
       x = x % w;
       y = y % h;
       // Draw Fill and outline for background of title Text
       int swidth = pad * 2 + font.stringWidth("Pie and Bar Samples");
       int title_x = (w - swidth)/2;
       g.setGrayScale(128);
       g.fillRoundRect(title_x, 0, swidth, fh, 5, 5);
       g.setGrayScale(0);
       g.drawRoundRect(title_x, 0, swidth, fh, 5, 5);
       // Sample Text
       g.setColor(0, 0, 0);
       g.drawString("Pie and Bar Samples", 
        title_x + pad, pad, Graphics.TOP|Graphics.LEFT);
 // Translate to below title text
       g.translate(0, titleHeight + pad);
       /*
  * Draw pie chart on the left side
  * using the barSize for width and height
  */
       g.setColor(255, 0, 0);
       g.fillArc(0, 0, pieSize, pieSize, 45, 270);
       g.setColor(0, 255, 0);
       g.fillArc(0, 0, pieSize, pieSize, 0, 45);
       g.setColor(0, 0, 255);
       g.fillArc(0, 0, pieSize, pieSize, 0, -45);
       g.setColor(0);
       g.drawArc(0, 0, pieSize, pieSize, 0, 360);
       // Draw Bar chart on right side of the display
       // scale the values to the pieSize maximum value
       int yorig = barSize;
       int h1 = barSize / 3, h2 = barSize / 2, h3 = barSize;
       int avg = (h1 + h2 + h3) / 3;
       // Move over to draw Bar chart
       g.translate((w + pad) / 2, 0);
       int bw = pieSize / 7;
       if (bw < 2)
            bw = 2;
       g.setColor(255, 0, 0);
       g.fillRect(bw*1, yorig-h1, bw+1, h1);
       g.setColor(0, 255, 0);
       g.fillRect(bw*3, yorig-h2, bw+1, h2);
       g.setColor(0, 0, 255);
       g.fillRect(bw*5, yorig-h3, bw+1, h3);
       g.setColor(0);
       g.drawRect(bw*1, yorig-h1, bw, h1);
       g.drawRect(bw*3, yorig-h2, bw, h2);
       g.drawRect(bw*5, yorig-h3, bw, h3);
       // Draw axis for bar chart.
       g.setGrayScale(0);
       g.drawLine(0, 0, 0, yorig);
       g.drawLine(0, yorig, barSize, yorig);
       g.setStrokeStyle(Graphics.DOTTED);
       g.drawLine(0, yorig - avg, barSize, yorig-avg);
       g.setStrokeStyle(Graphics.SOLID);
 // Restore to left and move down
       g.translate(-(w + pad) / 2, pieSize + pad);
       // Draw the key and pointer status
       g.setColor(128, 128, 128);
       int col1 = font.stringWidth("Action:");
       g.drawString("Key: ",      col1,     0,
        Graphics.TOP|Graphics.RIGHT);
       g.drawString(keyString(keyCode), col1, 0,
        Graphics.TOP|Graphics.LEFT);
       g.drawString("Action:",    col1,     fh,
        Graphics.TOP|Graphics.RIGHT);
       g.drawString(actionString(keyCode), col1, fh,
        Graphics.TOP|Graphics.LEFT);
       g.drawString("Event:",     col1,     fh*2,
        Graphics.TOP|Graphics.RIGHT);
       g.drawString(event,        col1,     fh*2,
        Graphics.TOP|Graphics.LEFT);
       int col2 = 80;
       g.drawString("x:",         col2,     0,
        Graphics.TOP|Graphics.RIGHT);
       g.drawString(Integer.toString(x), col2, 0,
        Graphics.TOP|Graphics.LEFT);
       g.drawString("y:",         col2,     fh,
        Graphics.TOP|Graphics.RIGHT);
       g.drawString(Integer.toString(y), col2, fh,
        Graphics.TOP|Graphics.LEFT);
       // Restore the origin and draw the crosshairs on top
       g.translate(-g.getTranslateX(), -g.getTranslateY());
       g.setColor(0, 0, 0);
       g.drawLine(x, y - 5, x, y + 5);
       g.drawLine(x - 5, y, x + 5, y);
   }

   String keyString(int keyCode) {
       if (keyCode == 0) {
           return "";
       }
       return Integer.toString(keyCode);
   }
   String actionString(int keyCode) {
       if (keyCode == 0) {
           return "";
       }
 int action = getGameAction(keyCode);
 switch (action) {
 case FIRE:
     return "Fire";
 case LEFT:
     return "Left";
 case RIGHT:
     return "Right";
 case DOWN:
     return "Down";
 case UP:
     return "Up";
 case GAME_A:
     return "Game A";
 case GAME_B:
     return "Game B";
 case GAME_C:
     return "Game C";
 case GAME_D:
     return "Game D";
 case 0:
     return "";
 default:
     return Integer.toString(action);
 }
   }

} 

      </source>



Capture Item Events

   <source lang="java">

/*--------------------------------------------------

  • CaptureItemEvents.java
  • Example from the book: Core J2ME Technology
  • Copyright John W. Muchow http://www.CoreJ2ME.ru
  • You may use/modify for any non-commercial purpose
  • -------------------------------------------------*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; public class CaptureItemEvents extends MIDlet implements ItemStateListener, CommandListener { 

 private Display display;      // Reference to Display object for this MIDlet
 private Form fmMain;         // The main Form
 private Command cmExit;      // A Command to exit the MIDlet
 private DateField dfDate;    // Display the date
 public CaptureItemEvents()
 {
   display = Display.getDisplay(this);
   // Create the date and populate with current date
   dfDate = new DateField("Date is:", DateField.DATE);
   dfDate.setDate(new java.util.Date());
   cmExit = new Command("Exit", Command.EXIT, 1);
   // Create the Form, add Command and DateField
   // listen for events from Command and DateField
   fmMain = new Form("Core J2ME");
   fmMain.addCommand(cmExit);
   fmMain.append(dfDate);
   fmMain.setCommandListener(this);     // Capture Command events (cmExit)
   fmMain.setItemStateListener(this);   // Capture Item events (dfDate)
 }
 // Called by application manager to start the MIDlet.
 public void startApp()
 {
   display.setCurrent(fmMain);
 }
 public void pauseApp()
 { }
 
 public void destroyApp(boolean unconditional)
 { }
 public void commandAction(Command c, Displayable s)
 {
   if (c == cmExit)
   {
     destroyApp(false);
     notifyDestroyed();
   } 
 }
 
 public void itemStateChanged(Item item)              
 {
   System.out.println("Inside itemStateChanged()");
   dfDate.setLabel("New Date: ");
 }

} 

      </source>



Commander

   <source lang="java">

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.lcdui.TextField; import javax.microedition.midlet.MIDlet; public class Commander extends MIDlet { 

 public void startApp() {
   Displayable d = new TextBox("TextBox", "Commander", 20, TextField.ANY);
   Command c = new Command("Exit", Command.EXIT, 0);
   d.addCommand(c);
   d.setCommandListener(new CommandListener() {
     public void commandAction(Command c, Displayable s) {
       notifyDestroyed();
     }
   });
   Display.getDisplay(this).setCurrent(d);
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) {
 }

} 


      </source>



Commands, Items, and Event Processing

   <source lang="java">

//jad file (please verify the jar size) /* MIDlet-Name: ThrowException MIDlet-Version: 1.0 MIDlet-Vendor: MyCompany MIDlet-Jar-URL: ThrowException.jar MIDlet-1: ThrowException, ThrowException.png, ThrowException MicroEdition-Configuration: CLDC-1.0 MicroEdition-Profile: MIDP-1.0 MIDlet-JAR-SIZE: 100

  • /

import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.StringItem; import javax.microedition.midlet.MIDlet; import javax.microedition.midlet.MIDletStateChangeException; public class ThrowException extends MIDlet implements CommandListener { 

 private Display display;
 private Form form = new Form("Throw Exception");
 private Command exit = new Command("Exit", Command.SCREEN, 1);
 private boolean isSafeToQuit = false;
 public ThrowException() {
   display = Display.getDisplay(this);
   form.addCommand(exit);
   form.setCommandListener(this);
 }
 public void startApp() {
   display.setCurrent(form);
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) throws MIDletStateChangeException {
   if (unconditional == false) {
     throw new MIDletStateChangeException();
   }
 }
 public void commandAction(Command command, Displayable displayable) {
   if (command == exit) {
     try {
       if (isSafeToQuit == false) {
         StringItem msg = new StringItem("Busy", "Please try again.");
         form.append(msg);
         destroyApp(false);
       } else {
         destroyApp(true);
         notifyDestroyed();
       }
     } catch (Exception exception) {
       isSafeToQuit = true;
     }
   }
 }

} 


      </source>



Many Commands

   <source lang="java">

/*--------------------------------------------------

  • TooManyCommands.java
  • Example from the book: Core J2ME Technology
  • Copyright John W. Muchow http://www.CoreJ2ME.ru
  • You may use/modify for any non-commercial purpose
  • -------------------------------------------------*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; public class TooManyCommands extends MIDlet implements CommandListener { 

 private Display display;      // Reference to Display object for this MIDlet
 private Form fmMain;          // The main Form  
 private TextBox tbAction;     // Textbox to show when user selects upload/download
 private Command cmExit;       // Exit the MIDlet
 private Command cmBack;       // Go "back" to the main form
 private Command cmUload;      // "upload" data - no real action done
 private Command cmDload;      // "download" data - no real action done
 
 public TooManyCommands()
 {
   display = Display.getDisplay(this);
   cmExit = new Command("Exit", Command.EXIT, 1);
   cmBack = new Command("Back", Command.BACK, 1);
   cmUload = new Command("Upload", Command.SCREEN, 2);        
   cmDload = new Command("Download", Command.SCREEN, 3);
   // Create the Form, add Commands, listen for events
   fmMain = new Form("Core J2ME");
   fmMain.addCommand(cmExit);
   fmMain.addCommand(cmUload);
   fmMain.addCommand(cmDload);
   fmMain.setCommandListener(this);    
   // Create a Textbox, add Command, listen for events
   tbAction = new TextBox("Process Data", "Upload/download data ", 25, 0);
   tbAction.addCommand(cmBack);
   tbAction.setCommandListener(this);      
 }
 // Called by application manager to start the MIDlet.
 public void startApp()
 {
   display.setCurrent(fmMain);
 }
 // A required method
 public void pauseApp()
 { }
 // A required method
 public void destroyApp(boolean unconditional)
 { }
 // Process events
 public void commandAction(Command c, Displayable s)
 {
   if (c == cmExit)
   {
     destroyApp(false);
     notifyDestroyed();
   }
   else if (c == cmUload || c == cmDload)
     display.setCurrent(tbAction);     
   else if (c == cmBack)
     display.setCurrent(fmMain);     
 }

} 

      </source>



Mapping Commands

   <source lang="java">

/*--------------------------------------------------

  • MappingCommands.java
  • Example from the book: Core J2ME Technology
  • Copyright John W. Muchow http://www.CoreJ2ME.ru
  • You may use/modify for any non-commercial purpose
  • -------------------------------------------------*/

import javax.microedition.midlet.*; import javax.microedition.lcdui.*; public class MappingCommands extends MIDlet implements CommandListener { 

 private Display display;      // Reference to Display object for this MIDlet
 private Form fmMain;          // Main Form  
 private TextBox tbHelp;       // Textbox to display help message
 private Command cmExit;       // Exit the MIDlet
 private Command cmHelp;       // Ask for Help
 private Command cmBack;       // Go "back" to the main form
 public MappingCommands()
 {
   display = Display.getDisplay(this);
   
   cmHelp = new Command("Help", Command.HELP, 1);
   cmBack = new Command("Back", Command.BACK, 1);
   cmExit = new Command("Exit", Command.EXIT, 1);
   
   // Create the Form, add Commands, listen for events
   fmMain = new Form("Core J2ME");
   fmMain.addCommand(cmExit);
   fmMain.addCommand(cmHelp);    
   fmMain.setCommandListener(this);
           
   // Create the help Textbox with a maximum of 25 characters
   tbHelp = new TextBox("Help", "Help text here...", 25, 0);
   tbHelp.addCommand(cmBack);
   tbHelp.setCommandListener(this);      

 }
 // Called by application manager to start the MIDlet.
 public void startApp()
 {
   display.setCurrent(fmMain);
 }
 // A required method
 public void pauseApp()
 { }
 // A required method
 public void destroyApp(boolean unconditional)
 { }
 // Process events
 public void commandAction(Command c, Displayable s)
 {
   if (c == cmExit)
   {
     destroyApp(false);
     notifyDestroyed();
   }
   else if (c == cmHelp)
     display.setCurrent(tbHelp);     
   else if (c == cmBack)
     display.setCurrent(fmMain);     
 }

} 


      </source>



Online Help

   <source lang="java">

// jad file /* MIDlet-Name: OnlineHelp MIDlet-Version: 1.0 MIDlet-Vendor: MyCompany MIDlet-Jar-URL: OnlineHelp.jar MIDlet-1: OnlineHelp, , OnlineHelp MicroEdition-Configuration: CLDC-1.0 MicroEdition-Profile: MIDP-1.0 MIDlet-JAR-SIZE: 100

  • /

import javax.microedition.lcdui.rumand; import javax.microedition.lcdui.rumandListener; import javax.microedition.lcdui.Display; import javax.microedition.lcdui.Displayable; import javax.microedition.lcdui.Form; import javax.microedition.lcdui.TextBox; import javax.microedition.midlet.MIDlet; public class OnlineHelp extends MIDlet implements CommandListener { 

 private Display display;
 private Command back = new Command("Back", Command.BACK, 2);
 private Command exit = new Command("Exit", Command.EXIT, 1);
 private Command help = new Command("Help", Command.HELP, 3);
 private Form form = new Form("Online Help Example");
 private TextBox helpMesg = new TextBox("Online Help", "Message.", 81, 0);
 public OnlineHelp() {
   display = Display.getDisplay(this);
   helpMesg.addCommand(back);
   form.addCommand(exit);
   form.addCommand(help);
   form.setCommandListener(this);
   helpMesg.setCommandListener(this);
 }
 public void startApp() {
   display.setCurrent(form);
 }
 public void pauseApp() {
 }
 public void destroyApp(boolean unconditional) {
 }
 public void commandAction(Command command, Displayable displayable) {
   if (command == back) {
     display.setCurrent(form);
   } else if (command == exit) {
     destroyApp(false);
     notifyDestroyed();
   } else if (command == help) {
     display.setCurrent(helpMesg);
   }
 }

} 


      </source>



Simple Command Demo

   <source lang="java">

/* 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.midlet.*; import javax.microedition.lcdui.*; public class HelloMIDlet extends MIDlet 

      implements CommandListener {
 // The exit command
 private Command exitCommand; 
 // The display for this MIDlet
 private Display display;    
 // create a ticker
 private Ticker hi = new Ticker("J2ME is cool"); 
 public HelloMIDlet() {
   display = Display.getDisplay(this);
   exitCommand = new Command("Exit", Command.SCREEN, 2);
 }
 public void startApp() {
   TextBox t = new TextBox("Hello MIDlet", 
               "Wireless Internet", 256, 0);
   t.addCommand(exitCommand);
   t.setCommandListener(this);
   t.setTicker(hi); // set the ticker
   display.setCurrent(t);
 }
 public void pauseApp() { }
 public void destroyApp(boolean unconditional) { }
 public void commandAction(Command c, Displayable s) {
   if (c == exitCommand) {
     destroyApp(false);
     notifyDestroyed();
   }
 }

} 


      </source>



Various Event

   <source lang="java">

/* Learning Wireless Java Help for New J2ME Developers By Qusay Mahmoud ISBN: 0-596-00243-2

  • /

import javax.microedition.lcdui.*; import javax.microedition.midlet.*; public class VariousEvent extends MIDlet implements CommandListener { 

  // display manager
  Display display = null;
   
  // a menu with items
  List menu = null; // main menu
  // list of choices
  List choose = null;
  // textbox
  TextBox input = null;
  // ticker
  Ticker ticker = new Ticker("Test GUI Components");
  // alerts
  final Alert soundAlert = new Alert("sound Alert");
  // date
  DateField date = new DateField("Today"s date: ", DateField.DATE);
  // form
  Form form = new Form("Form for Stuff");
    
  // gauge
  Gauge gauge = new Gauge("Gauge Label", true, 10, 0);
  // text field
  TextField textfield = new TextField("TextField Label", "abc", 50, 0);
  // command
  static final Command backCommand = new Command("Back", Command.BACK, 0);
  static final Command mainMenuCommand = new Command("Main", Command.SCREEN, 1);
  static final Command exitCommand = new Command("Exit", Command.STOP, 2);
  String currentMenu = null;
  // constructor.
  public VariousEvent() {
  }
  /**
   * Start the MIDlet by creating a list of items and associating the
   * exit command with it.
   */
  public void startApp() throws MIDletStateChangeException {
    display = Display.getDisplay(this);
    // open a db stock file
    menu = new List("Test Components", Choice.IMPLICIT);
    menu.append("Test TextBox", null);
    menu.append("Test List", null);
    menu.append("Test Alert", null);
    menu.append("Test Date", null);
    menu.append("Test Form", null);
    menu.addCommand(exitCommand);
    menu.setCommandListener(this);
    menu.setTicker(ticker);
    mainMenu();
  }
  public void pauseApp() {
    display = null;
    choose = null;
    menu = null;
    ticker = null;
    form = null;
    input = null;
    gauge = null;
    textfield = null;      
  }
  public void destroyApp(boolean unconditional) {
    notifyDestroyed();
  }
  // main menu
  void mainMenu() {
    display.setCurrent(menu);
    currentMenu = "Main"; 
  }
  /**
   * Test the TextBox component.
   */
  public void testTextBox() {
    input = new TextBox("Enter Some Text:", "", 5, TextField.ANY);
    input.setTicker(new Ticker("testTextBox"));
    input.addCommand(backCommand);
    input.setCommandListener(this);
    input.setString("");
    display.setCurrent(input);
    currentMenu = "input";
  }
  
  /**
   * Test the List component.
   */
  public void testList() {
     choose = new List("Choose Items", Choice.MULTIPLE);
     choose.setTicker(new Ticker("listTest"));
     choose.addCommand(backCommand);
     choose.setCommandListener(this);
     choose.append("Item 1", null);
     choose.append("Item 2", null);
     choose.append("Item 3", null);
     display.setCurrent(choose);
     currentMenu = "list"; 
  }
  /**
   * Test the Alert component.
   */
  public void testAlert() {
     soundAlert.setType(AlertType.ERROR);
     soundAlert.setString("** ERROR **");
     display.setCurrent(soundAlert);
  }
  /**
   * Test the DateField component.
   */
  public void testDate() {
     java.util.Date now = new java.util.Date();
     date.setDate(now);
     Form f = new Form("Today"s date");
     f.append(date);
     f.addCommand(backCommand);
     f.setCommandListener(this);
     display.setCurrent(f);
     currentMenu = "date";
  }
  /**
   * Test the Form component.
   */
  public void testForm() {
     form.append(gauge);
     form.append(textfield);
     form.addCommand(backCommand);
     form.setCommandListener(this);
     display.setCurrent(form);
     currentMenu = "form";
  }
  /**
   * Handle events.
   */  
  public void commandAction(Command c, Displayable d) {
     String label = c.getLabel();
     if (label.equals("Exit")) {
        destroyApp(true);
     } else if (label.equals("Back")) {
        if(currentMenu.equals("list") || currentMenu.equals("input") || 
           currentMenu.equals("date") || currentMenu.equals("form")) {
           // go back to menu
           mainMenu();
        } 
     } else {
        List down = (List)display.getCurrent();
        switch(down.getSelectedIndex()) {
           case 0: testTextBox();break;
           case 1: testList();break;
           case 2: testAlert();break;
           case 3: testDate();break;
           case 4: testForm();break;
        }
     }
  }

} 


      </source>
Источник — «http://jexp.ru/index.php?title=Java/J2ME/Event_Command&oldid=7289»