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Revision as of 07:46, 10 May 2012 by hamishwillee (Talk | contribs)

Creating CustomItem in Java ME

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Article Metadata
Code ExampleTested with
Devices(s): Nokia 6131, Nokia E70, Nokia N78
Compatibility
Platform(s): Series 40 3rd Edition, FP1, S60 3rd Edition, S60 3rd Edition, FP1, S60 3rd Edition, FP2
Series 40
Series 40 6th Edition FP1
Series 40 3rd Edition FP1
Symbian
S60 3rd Edition FP2
S60 3rd Edition FP1
S60 3rd Edition (initial release)
Article
Keywords: javax.microedition.lcdui.CustomItem
Created: vltsoy (27 Nov 2008)
Last edited: hamishwillee (10 May 2012)


Contents

Overview

This code snippet demonstrates how to create and display custom control. It consist of two files:

1. CustomControl.java - Inherited from MIDlet, displays the MyItem control.

2. MyItem.java - Inherited from CustomItem.

Custom contol class MyItem implements the method keyPressed(), which is responsible for storing the last key-pressed code. It also implements the paint() method, which displays the last key-pressed code inside the control.


Source file: CustomControl.java

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.midlet.MIDlet;
 
 
 
public class CustomControl extends MIDlet implements CommandListener{
//Main form.
 
private Form form;
private Display display;
private Command exitCommand;
private MyItem myItem;
 
/**
* Constructor. Constructs the object and initializes displayables.
*/

public CustomControl() {
form = new Form("Custom Control MIDlet.");
 
// Add command buttons
exitCommand = new Command("Exit", Command.EXIT, 1);
form.addCommand(exitCommand);
form.setCommandListener(this);
 
display = Display.getDisplay(this);
display.setCurrent(form);
 
myItem = new MyItem("Custom control");
form.append(myItem);
}
 
/**
* From CommandListener.
* Called by the system to indicate that a command has been invoked on a
* particular displayable.
* @param cmd the command that was invoked
* @param displayable the displayable where the command was invoked
*/

public void commandAction(Command cmd, Displayable displayable) {
if (cmd == exitCommand) {
notifyDestroyed();
}
}
 
/**
* From MIDlet.
* Called when the MIDlet is started.
*/

public void startApp() {
// No implementation required.
}
 
/**
* From MIDlet.
* Called to signal the MIDlet to enter the Paused state.
*/

public void pauseApp() {
// No implementation required.
}
 
/**
* From MIDlet.
* Called to signal the MIDlet to terminate.
* @param unconditional whether the MIDlet has to be unconditionally
* terminated
*/

public void destroyApp(boolean unconditional) {
// No implementation required.
}
}

Source file: MyItem.java

import javax.microedition.lcdui.CustomItem;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
 
class MyItem extends CustomItem {
// Last key pressed code.
private int key;
 
/**
* Constructor.
*/

public MyItem( String label ){
super( "" );
}
 
/**
* From CustomItem.
* Called by the system to redraw canvas.
* @param graphics used for drawing operations.
*/

public void paint(Graphics g, int width, int height) {
//Display last key pressed.
String output = "Key code:"+String.valueOf(key);
 
g.drawString(output,(width-g.getFont().stringWidth(output))/2,
(height-g.getFont().getHeight())/2, 0);
 
g.setStrokeStyle(Graphics.DOTTED);
for (int i= 0;i<(height+width)/10;i++)
{
g.setColor(i*10000);
g.drawRect( 0+i, 0+i, (width-i*2), (height-i*2));
}
}
 
/**
* From CustomItem.
* Called by the system to retrieve minimum width required for this control.
*/

protected int getMinContentWidth() {
return 150;
}
 
/**
* From CustomItem.
* Called by the system to retrieve minimum height required for this control.
*/

protected int getMinContentHeight() {
return 100;
}
 
/**
* From CustomItem.
* Called by the system to retrieve preferred width for this control.
*/

protected int getPrefContentWidth(int arg0) {
return 200;
}
 
/**
* From CustomItem.
* Called by the system to retrieve preferred height for this control.
*/

protected int getPrefContentHeight(int arg0) {
return 100;
}
 
/**
* From CustomItem.
* Called by the system to redraw canvas.
* @param graphics used for drawing operations.
*/

protected void keyPressed(int keyCode) {
key = keyCode;
this.repaint();
}
}

Postconditions

After starting the MIDlet, the user will see custom control with the last key-pressed code.

Supplementary material

You can view the source file and executable application in the attached zip archive. The archive is available for download at Media:Creating custom control in J2ME.zip

Related articles:

LCDUI CustomItem content remains blank when appended to a Form before setting the Form as current Displayable (Known Issue)

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