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Controlling Light settings in Java ME

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This snippet shows how to control the lighting on devices through the setLights() method of the DeviceControl class.

Article Metadata
Code ExampleTested with
Devices(s): Nokia 6131, Nokia N81, Nokia 701, Nokia Asha 305
CompatibilityArticle
Created: IlGolub (28 Nov 2008)
Reviewed: mtilli (15 Aug 2012)
Last edited: hamishwillee (08 Aug 2013)

Source file: ControllingLightMIDlet.java

import com.nokia.mid.ui.DeviceControl;
 
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 ControllingLightMIDlet extends MIDlet implements CommandListener {
/**
* Command for setting light
*/

private Command controllingLightCommand;
/**
* exit midlet command
*/

private Command exitCommand;
 
private Form mainForm;
 
/**
* The ControllingLightMIDlet constructor.
*/

public ControllingLightMIDlet() {
//Empty implementation
}
 
/**
* Performs an action assigned to the Mobile Device - MIDlet Started point.
*/

public void startMIDlet() {
switchDisplayable(getForm());
}
 
/**
* Switches a current displayable in a display. The Display instance is
* taken from getDisplay() method. This method is used by all actions
* in the design for switching displayable.
* @param nextDisplayable the Displayable to be set
*/

public void switchDisplayable(Displayable nextDisplayable) {
Display display = getDisplay();
display.setCurrent(nextDisplayable);
}
 
/**
* From CommandListener.
* Called by a system to indicated that a command has been invoked on a
* particular displayable.
* @param command the Command that was invoked
* @param displayable the Displayable where the command was invoked
*/

public void commandAction(Command command, Displayable displayable) {
if (displayable == mainForm) {
if (command == exitCommand) {
exitMIDlet();
} else if(command == controllingLightCommand) {
//up light level from 0 to 100
for(int i = 0; i < 100; i++) {
// void setLights(int num, int level) is a static function of
//com.nokia.mid.ui.DeviceControl class that
//activates and deactivates the lights on the device.
//Parameter num indicates the number of the device light
//to control. Currently only one num parameter value is
//specified: num value 0 is used for controlling the
//screen backlight. Parameter level is a value between
//0-100, which indicates the brightness of the light.
//In many implementations, there are only two levels:
//on or off(Sony Ericsson). Value 0 indicates lights off
//for monochrome displays or the minimum brightness setting
//for color displays. All other level values (1-100) are
//used for turning the lights on, possibly with different
//brightness levels, depending on the value. A larger value
//always results in either the same brightness setting as a
//lower one, or a brighter setting. For many products,
//values 1-100 will just turn the lights on.
DeviceControl.setLights(0, i);
try {
Thread.sleep(30);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
}
}
/**
* Returns an initiliazed instance of mainForm component.
* @return the initialized component instance
*/

public Form getForm() {
if (mainForm == null) {
mainForm = new Form("Lighting test!");
 
exitCommand = new Command("Exit", Command.EXIT, 0);
mainForm.addCommand(exitCommand);
controllingLightCommand = new Command("Light", Command.SCREEN, 0);
mainForm.addCommand(controllingLightCommand);
mainForm.setCommandListener(this);
}
return mainForm;
}
 
/**
* Returns a display instance.
* @return the display instance.
*/

public Display getDisplay () {
return Display.getDisplay(this);
}
 
/**
* Exits MIDlet.
*/

public void exitMIDlet() {
switchDisplayable(null);
destroyApp(true);
notifyDestroyed();
}
 
/**
* From MIDlet.
* Called when MIDlet is started.
* Checks whether the MIDlet have been already started and
* initialize/starts or resumes the MIDlet.
*/

public void startApp() {
switchDisplayable(getForm());
}
 
/**
* From MIDlet.
* Called when MIDlet is paused.
*/

public void pauseApp() {
//Empty implementation
}
 
/**
* From MIDlet.
* Called to signal the MIDlet to terminate.
* @param unconditional if true, then the MIDlet has to be unconditionally
* terminated and all resources has to be released.
*/

public void destroyApp(boolean unconditional) {
//Empty implementation
}
}


Postconditions

This MIDlet implements a simple example of controlling the light property.

Turns off the light then raises the light level from 1 to 100.

Supplementary material

You can download this application and source code here: Controlling Light Settings.zip

Related articles:

Flashing the backlight using Java ME

How to block the screen saver

This page was last modified on 8 August 2013, at 07:37.
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